Prof. Dr. Jochen Stefan Gutmann

Physical Chemistry
University of Duisburg-Essen

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  • Immobilization of peroxidase on textile carrier materials and their application in the bleaching of colored whey
    Courth, K. and Binsch, M. and Ali, W. and Ingenbosch, K. and Zorn, H. and Hoffmann-Jacobsen, K. and Gutmann, J.S. and Opwis, K.
    Journal of Dairy Science 104 (2021)
    Textiles represent promising support materials for enzymes. The goal of the present work was to investigate the immobilization of commercial peroxidase on a polyester needle felt and the repeated use in the gentle degradation of norbixin in whey from dairy cheese as a practical application. High enzyme loads were obtained by a 2-step immobilization procedure. First, the number of functional groups on the textile surface was increased by a modification with amino-functional polyvinylamine. Second, the enzyme was immobilized by using 2 types of crosslinking agents. Due to the iron content of peroxidase, inductively coupled plasma–optical emission spectrometry was used for the quantitative determination of the enzyme load on the textile. The enzyme activity was evaluated using common 2,2'-azino-di-(3-ethylbenzthiazoline-6-sulfonic acid) assay for peroxidases. By the variation of enzyme input and crosslinker concentration, a maximal enzyme load of 80 mg/g of textile was achieved, and a maximum specific activity of 57 U/g of textile. For the visualization of the enzyme on the fiber surface, fluorescence microscopy as well as scanning probe microscopy were used. The immobilized peroxidase showed significant activity, even after 50 reuse cycles. In addition, the potential of the new support and enzyme combination in commercial whey bleaching was demonstrated successfully on a 10-L scale. © 2021 American Dairy Science Association
    view abstract10.3168/jds.2019-17110
  • NIR-Sensitized Cationic and Hybrid Radical/Cationic Polymerization and Crosslinking
    Pang, Y. and Shiraishi, A. and Keil, D. and Popov, S. and Strehmel, V. and Jiao, H. and Gutmann, J.S. and Zou, Y. and Strehmel, B.
    Angewandte Chemie - International Edition 60 (2021)
    NIR-sensitized cationic polymerization proceeded with good efficiency, as was demonstrated with epoxides, vinyl ether, and oxetane. A heptacyanine functioned as sensitizer while iodonium salt served as coinitiator. The anion adopts a special function in a series selected from fluorinated phosphates (a: [PF6]−, b: [PF3(C2F5)3]−, c: [PF3(n-C4F9)3]−), aluminates (d: [Al(O-t-C4F9)4]−, e: [Al(O(C3F6)CH3)4]−), and methide [C(O-SO2CF3)3]− (f). Vinyl ether showed the best cationic polymerization efficiency followed by oxetanes and oxiranes. DFT calculations provided a rough pattern regarding the electrostatic potential of each anion where d showed a better reactivity than e and b. Formation of interpenetrating polymer networks (IPNs) using trimethylpropane triacrylate and epoxides proceeded in the case of NIR-sensitized polymerization where anion d served as counter ion in the initiator system. No IPN was formed by UV-LED initiation using the same monomers but thioxanthone/iodonium salt as photoinitiator. Exposure was carried out with new NIR-LED devices emitting at either 805 or 870 nm. © 2020 The Authors. Published by Wiley-VCH GmbH
    view abstract10.1002/anie.202010746
  • A flame-retardant phytic-acid-based LbL-coating for cotton using polyvinylamine
    Zilke, O. and Plohl, D. and Opwis, K. and Mayer-Gall, T. and Gutmann, J.S.
    Polymers 12 (2020)
    Phytic acid (PA), as a natural source of phosphorus, was immobilized on cotton (CO) in a layer-by-layer (LbL) approach with polyvinylamine (PVAm) as the oppositely charged electrolyte to create a partly bio-based flame-retardant finish. PVAm was employed as a synthetic nitrogen source with the highest density of amine groups of all polymers. Vertical flame tests revealed a flame-retardant behavior with no afterflame and afterglow time for a coating of 15 bilayers (BL) containing 2% phosphorus and 1.4% nitrogen. The coating achieved a molar P:N ratio of 3:5. Microscale combustion calorimetry (MCC) analyses affirmed the flame test findings by a decrease in peak heat release rate (pkHRR) by more than 60% relative to unfinished CO. Thermogravimetric analyses (TGA) and MCC measurements exhibited a shifted CO peak to lower temperatures indicating proceeding reactions to form an isolating char on the surface. Fourier transform infrared spectroscopy (FTIR) coupled online with a TGA system, allowed the identification of a decreased amount of acrolein, methanol, carbon monoxide and formaldehyde during sample pyrolysis and a higher amount of released water. Thereby the toxicity of released volatiles was reduced. Our results prove that PA enables a different reaction by catalyzing cellulosic dehydration, which results in the formation of a protective char on the surface of the burned fabric. © 2020 by the authors.
    view abstract10.3390/POLYM12051202
  • Dyeing of m-aramid fibers in ionic liquids
    Opwis, K. and Celik, B. and Benken, R. and Knittel, D. and Gutmann, J.S.
    Polymers 12 (2020)
    Aramids represent a class of high-performance fibers with outstanding properties and manifold technical applications, e.g., in flame-retardant protective clothing for firefighters and soldiers. However, the dyeing of aramid fibers is accompanied by several economic and ecological disadvantages, resulting in a high consumption ofwater, energy and chemicals. In this study, a newand innovative dyeing procedure form-aramid fibers using ionic liquids (ILs) is presented. Themost relevant parameters of IL-dyed fibers, such as tensile strength, elongation and fastness towards washing, rubbing and light, were determined systematically. In summary, all aramid textiles dyed in ILs show similar or even better results than the conventionally dyed samples. In conclusion, we have successfully paved the way for a new, eco-friendly and more sustainable dyeing process for aramids in the near future. © 2020 by the authors.
    view abstract10.3390/polym12081824
  • Enzymatic epoxidation of cyclohexene by peroxidase immobilization on a textile and an adapted reactor design
    Wunschik, D.S. and Ingenbosch, K.N. and Süss, P. and Liebelt, U. and Quint, S. and Dyllick-Brenzinger, M. and Zuhse, R. and Menyes, U. and Hoffmann-Jacobsen, K. and Opwis, K. and Gutmann, J.S.
    Enzyme and Microbial Technology 136 (2020)
    A textile-based reaction system for new peroxidase reactions in non-native media was implemented. The epoxidation of cyclohexene by the commercial peroxidase MaxiBright® was realized with the textile-immobilized enzyme in an adapted liquid-liquid two-phase reactor. A commercially available polyester felt was used as low-price carrier and functionalized with polyvinyl amine. The covalent immobilization with glutardialdehyde lead to an enzyme loading of 0.10 genzyme/gtextile. The textile-based peroxidase shows a high activity retention in the presence of organic media. This catalyst is shown to enable the epoxidation of cyclohexene in various solvents as well as under neat conditions. A model reactor was produced by 3D printing which places the textile catalyst at the interphase between the liquid reaction phase and the product extracting solvent. © 2020 Elsevier Inc.
    view abstract10.1016/j.enzmictec.2020.109512
  • Investigation of roughness correlation in polymer brushes via X-ray scattering
    Hildebrandt, M. and Shin, E. and Yang, S. and Ali, W. and Altinpinar, S. and Gutmann, J.S.
    Polymers 12 (2020)
    Thin polymer films and coatings are used to tailor the properties of surfaces in various applications such as protection against corrosion, biochemical functionalities or electronic resistors. Polymer brushes are a certain kind of thin polymer films, where polymer chains are covalently grafted to a substrate and straighten up to form a brush structure. Here we report on differences and similarities between polymer brushes and spin-coated polymer films from polystyrene and polymethyl methacrylate with special emphasis on surface roughness and roughness correlation. The phenomenon of roughness correlation or conformality describes the replication of the roughness profile from the substrate surface to the polymer surface. It is of high interest for polymer physics of brush layers as well as applications, in which a homogeneous polymer layer thickness is required. We demonstrate that spin-coated films as well as polymer brushes show roughness correlation, but in contrast to spin-coated films, the correlation in brushes is stable to solvent vapor annealing. Roughness correlation is therefore an intrinsic property of polymer brushes. © 2020 by the authors.
    view abstract10.3390/POLYM12092101
  • NIR Light-Induced ATRP for Synthesis of Block Copolymers Comprising UV-Absorbing Moieties
    Kütahya, C. and Meckbach, N. and Strehmel, V. and Gutmann, J.S. and Strehmel, B.
    Chemistry - A European Journal 26 (2020)
    NIR exposure at 790 nm activated photopolymerization of monomers comprising UV-absorbing moieties by using [CuII/(TPMA)]Br2 (TPMA=tris(2-pyridylmethyl)amine) in the ppm range and an alkyl bromide as initiator. Some of them comprised structural elements selected either from those showing proton transfer or photocycloaddition upon UV excitation. Polymers obtained comprise living end groups serving as macroinitiator for controlled synthesis of block copolymers with relatively narrow molecular weight distributions. Chromatographic results indicated formation of block copolymers produced by this synthetic approach. Free-radical polymerization of monomers pursued for comparison exhibited the expected broader dispersity of molecular weight compared to photo-ATRP. Polymerization of these monomers by UV photo-ATRP failed on the contrary to NIR photo-ATRP demonstrating the UV-filter function of the monomers. This work conclusively provides a new approach for the polymerization of monomers comprising UV-absorbing moieties through photo-ATRP in the NIR region. This occurred in a simple and efficient pathway. However, studies also showed that not all monomers chosen successfully proceeded in the NIR photo-ATRP protocol. © 2020 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA
    view abstract10.1002/chem.202001099
  • Porous ultra-thin films from photocleavable block copolymers: In-situ degradation kinetics study of pore material
    Altinpinar, S. and Ali, W. and Schuchardt, P. and Yildiz, P. and Zhao, H. and Theato, P. and Gutmann, J.S.
    Polymers 12 (2020)
    On the basis of the major application for block copolymers to use them as separation membranes, lithographic mask, and as templates, the preparation of highly oriented nanoporous thin films requires the selective removal of the minor phase from the pores. In the scope of this study, thin film of polystyrene-block-poly(ethylene oxide) block copolymer with a photocleavable junction groups based on ortho-nitrobenzylester (ONB) (PS-h-PEO) was papered via the spin coating technique followed by solvent annealing to obtain highly-ordered cylindrical domains. The polymer blocks are cleaved by means of a mild UV exposure and then the pore material is washed out of the polymer film by ultra-pure water resulting in arrays of nanoporous thin films to remove one block. The removal of the PEO materials from the pores was proven using the grazing-incidence small-angle X-ray scattering (GISAXS) technique. The treatment of the polymer film during the washing process was observed in real time after two different UV exposure time (1 and 4 h) in order to draw conclusions regarding the dynamics of the removal process. In-situ X-ray reflectivity measurements provide statistically significant information about the change in the layer thickness as well as the roughness and electron density of the polymer film during pore formation. 4 H UV exposure was found to be more efficient for PEO cleavage. By in-situ SFM measurements, the structure of the ultra-thin block copolymer films was also analysed and, thus, the kinetics of the washing process was elaborated. The results from both measurements confirmed that the washing procedure induces irreversible change in morphology to the surface of the thin film. © 2020 by the authors.
    view abstract10.3390/POLYM12040781
  • Singlet-Oxygen Generation by Peroxidases and Peroxygenases for Chemoenzymatic Synthesis
    Ingenbosch, K.N. and Quint, S. and Dyllick-Brenzinger, M. and Wunschik, D.S. and Kiebist, J. and Süss, P. and Liebelt, U. and Zuhse, R. and Menyes, U. and Scheibner, K. and Mayer, C. and Opwis, K. and Gutmann, J.S. and Hoffmann-Jacobsen, K.
    ChemBioChem (2020)
    Singlet oxygen is a reactive oxygen species undesired in living cells but a rare and valuable reagent in chemical synthesis. We present a fluorescence spectroscopic analysis of the singlet-oxygen formation activity of commercial peroxidases and novel peroxygenases. Singlet-oxygen sensor green (SOSG) is used as fluorogenic singlet oxygen trap. Establishing a kinetic model for the reaction cascade to the fluorescent SOSG endoperoxide permits a kinetic analysis of enzymatic singlet-oxygen formation. All peroxidases and peroxygenases show singlet-oxygen formation. No singlet oxygen activity could be found for any catalase under investigation. Substrate inhibition is observed for all reactive enzymes. The commercial dye-decolorizing peroxidase industrially used for dairy bleaching shows the highest singlet-oxygen activity and the lowest inhibition. This enzyme was immobilized on a textile carrier and successfully applied for a chemical synthesis. Here, ascaridole was synthesized via enzymatically produced singlet oxygen. © 2020 Wiley-VCH GmbH
    view abstract10.1002/cbic.202000326
  • Tuning the density of zwitterionic polymer brushes on PET fabrics by aminolysis: Effect on antifouling performances
    Lorusso, E. and Ali, W. and Leniart, M. and Gebert, B. and Oberthür, M. and Gutmann, J.S.
    Polymers 12 (2020)
    Here, we synthesize zwitterionic polymer brushes on polyester fabrics by atom transfer radical polymerization (ATRP) after a prefunctionalization step involving an aminolysis reaction with ethylenediamine. Aminolysis is an easy method to achieve homogeneous distributions of functional groups on polyester fibers (PET) fabrics. Varying the polymerization time and the prefunctionalization conditions of the reaction, it is possible to tune the amount of water retained over the surface and study its effect on protein adhesion. This study revealed that the polymerization time plays a major role in preventing protein adhesion on the PET surface. © 2019 by the authors.
    view abstract10.3390/polym12010006
  • A green water‐soluble cyclophosphazene as a flame retardant finish for textiles
    Mayer‐Gall, T. and Plohl, D. and Derksen, L. and Lauer, D. and Neldner, P. and Ali, W. and Fuchs, S. and Gutmann, J.S. and Opwis, K.
    Molecules 24 (2019)
    Poly and cyclophosphazenes are excellent flame retardants but currently, are not used as textile finishing agents because watersoluble and permanent washing systems are missing. Here, we demonstrate for the first time, the successful usage of a watersoluble cyclotriphosphazene derivative for textile finishing for cotton, different cotton/polyester, and cotton/polyamide blend fabrics. A durable finish was achieved using a photoinduced grafting reaction. The flame retardant properties of the various fabrics were improved with a higher limiting oxygen index, a reduced heat release rate, and an exhibition of intumescent. Furthermore, the finished textiles passed several standardized flammability tests. © 2019 by the authors.
    view abstract10.3390/molecules24173100
  • Abrasion resistance of textiles: Gaining insight into the damaging mechanisms of different test procedures
    Textor, T. and Derksen, L. and Bahners, T. and Gutmann, J.S. and Mayer-Gall, T.
    Journal of Engineered Fibers and Fabrics 14 (2019)
    Three established test methods employed for evaluating the abrasion or wear resistance of textile materials were compared to gain deeper insight into the specific damaging mechanisms to better understand a possible comparability of the results of the different tests. The knowledge of these mechanisms is necessary for a systematic development of finishing agents improving the wear resistance of textiles. Martindale, Schopper, and Einlehner tests were used to analyze two different fabrics made of natural (cotton) or synthetic (polyethylene terephthalate) fibers, respectively. Samples were investigated by digital microscopy and scanning electron microscopy to visualize the damage. Damage symptoms are compared and discussed with respect to differences in the damaging mechanisms. © The Author(s) 2019.
    view abstract10.1177/1558925019829481
  • Aroma Molecules as Dynamic Volatile Surfactants: Functionality beyond the Scent
    Soboleva, O.A. and Protsenko, P.V. and Korolev, V.V. and Viktorova, J. and Yakushenko, A. and Kudla, R. and Gutmann, J.S. and Tsarkova, L.A.
    ACS Applied Materials and Interfaces 11 (2019)
    Understanding of nonequilibrium processes at dynamic interfaces is indispensable for advancing design and fabrication of solid-state and soft materials. The research presented here unveils specific interfacial behavior of aroma molecules and justifies their usage as multifunctional volatile surfactants. As nonconventional volatile amphiphiles, we study commercially available poorly water-soluble compounds from the classes of synthetic and essential flavor oils. Their disclosed distinctive feature is a high dynamic interfacial activity, so that they decrease the surface tension of aqueous solutions on a time scale of milliseconds. Another potentially useful property of such amphiphiles is their volatility, so that they notably evaporate from interfaces on a time scale of seconds. This behavior allows for control of wetting and spreading processes. A revealed synergetic interfacial behavior of mixtures of conventional and volatile surfactants is attributed to a decrease of the activation barrier as a result of high statistical availability of new sites at the surface upon evaporation of the volatile component. Our results offer promising advantages in manufacturing technologies which involve newly creating interfaces, such as spraying, coating technologies, ink-jet printing, microfluidics, laundry, and stabilization of emulsions in cosmetic and food industry, as well as in geosciences for controlling aerosol formation. Copyright © 2019 American Chemical Society.
    view abstract10.1021/acsami.9b15596
  • Electrical conductivity of silver nanoparticle doped carbon nanofibres measured by CS-AFM
    Ali, W. and Shabani, V. and Linke, M. and Sayin, S. and Gebert, B. and Altinpinar, S. and Hildebrandt, M. and Gutmann, J.S. and Mayer-Gall, T.
    RSC Advances 9 (2019)
    In this work, a pioneering study on the electrical properties of composite carbon nanofibres (CNFs) using current-sensitive atomic force microscopy (CS-AFM) has been demonstrated. CNFs are highly interesting materials which are usable in a wide array of applications e.g. electrode materials for biosensors, lithium ion batteries, fuel cells and supercapacitors. CNFs offer a high specific surface area and thus have a high contact area for charge transfer. CNFs can be produced using spinnable polyacrylonitrile (PAN) as a precursor for carbonisation. For the purpose of developing efficient CNFs with high conductivity and power density, silver nanoparticle (AgNPs)-containing PAN solutions were electrospun to form composite nanofibres which was followed by heat treatment. The applied voltage of the spinning setup and the content of both PAN and the silver nanoparticles in the spinning solution were varied in order to study their influence on the morphology and the electrical properties of the nanofibres. The resultant morphologies and fibre diameters were determined by scanning electron microscopy (SEM). The formation of silver nanoparticles was characterised in solution by UV-visible absorption spectroscopy and dynamic light scattering (DLS), while energy-dispersive X-ray spectroscopy (EDX) and transmission electron microscopy (TEM) were carried out to investigate the presence as well as the average diameter of the AgNPs. The electrical properties of the CNFs were investigated using CS-AFM. This technique gives us the possibility to explore the electrical properties of single fibers and hence derive relationships between the structural features and the electrical properties. Our results show that the composite CNFs have a higher electrical conductivity than the neat CNFs and both the average diameter of the fibers and the electrical conductivity increase with an increasing AgNP content. © The Royal Society of Chemistry.
    view abstract10.1039/C8RA04594A
  • Hydrogel functionalized polyester fabrics by UV-induced photopolymerization
    Lorusso, E. and Ali, W. and Hildebrandt, M. and Mayer-Gall, T. and Gutmann, J.S.
    Polymers 11 (2019)
    We address a strategy to graft hydrogels onto polyethylene terephthalate (PET) fabrics using different acrylate-based monomers. The hydrogel-modified fabrics were prepared by a two-step modification. To this end, double functional groups were firstly introduced onto the PET surface via an aminolysis reaction involving allylamine. The final grafted polymer networks were then obtained after UV-induced radical photopolymerization by varying acrylate monomer types in the presence of a cross-linker. After characterization, the resulting hydrogels showed different morphologies and abrasion resistance performances depending on their chemical nature. UV-photopolymerization is a fast and low-cost method to achieve technical fabrics with specific desired properties. © 2019 by the author.
    view abstract10.3390/polym11081329
  • In Situ Monitoring Mesoscopic Deformation of Nanostructured Porous Titania Films Caused by Water Ingression
    Song, L. and Rawolle, M. and Hohn, N. and Gutmann, J.S. and Frielinghaus, H. and Müller-Buschbaum, P.
    ACS Applied Materials and Interfaces 11 (2019)
    Nanostructured porous titania films are used in many energy-related applications. In this work, the temporal evolution of the mesoscopic deformation of mesoporous titania films synthesized via block copolymer-assisted sol-gel chemistry is investigated with in situ grazing incidence small-angle neutron scattering (GISANS) during exposure to D2O vapor. Two types of mesoporous titania films are compared, which have a different degree of structural stability, depending on the applied annealing temperature (400 °C vs 600 °C) in a nitrogen atmosphere. Water ingression causes a gradual structure deformation in terms of decreasing center-to-center distances and broadening of the size distribution of the titania nanostructures. Based on the evolution of the mesopore size obtained from in situ GISANS measurements, the results show that structures synthesized at lower temperature undergo a stronger deformation because of the lower elastic modulus originating from larger pores, despite having a higher degree of order. © 2019 American Chemical Society.
    view abstract10.1021/acsami.9b10750
  • Microplastic fibers released by textile laundry: A new analytical approach for the determination of fibers in effluents
    Haap, J. and Classen, E. and Beringer, J. and Mecheels, S. and Gutmann, J.S.
    Water (Switzerland) 11 (2019)
    The detection of shedded fibers in effluents from textile washing has attracted much attention due to its reported contribution to microplastic pollution. Commonly used analytical methods for fiber detection in liquids are based on filtration with subsequent microscopic analysis and/or gravimetric weighing. These approaches are time-consuming and prone to errors. In this study, an approach based on dynamic image analysis was applied in order to set up an efficient method to analyze fibers in effluents from washing processes. In an initial validation step, reliable information on the counts of fibers and the morphological characteristics were confirmed. For wastewaters from polyester-cotton blends, the chemical nature of the fiber debris (natural vs. synthetic origin) was determined by combining the dynamic image analysis with a chemical pretreatment. In this study, dynamic image analysis was revealed as a rapid, non-destructive, precise, and reliable technology for the characterization and quantification of the fiber debris, offering a promising approach for fiber analysis in liquids. © 2019 by the authors.
    view abstract10.3390/w11102088
  • Nonfouling textiles with tunable antimicrobial activity based on a zwitterionic polyamine finish
    Timma, L.M. and Lewald, L. and Gier, F. and Homey, L. and Neyer, C. and Nickisch-Hartfiel, A. and Gutmann, J.S. and Oberthür, M.
    RSC Advances 9 (2019)
    Antimicrobial finishes for textiles and other surfaces that act without the release of biocides to the environment (contact biocides) or by inhibiting microbial adhesion (antifouling action) are viewed as promising and environmentally friendly alternatives to current products. We have used polyvinylamine polymers that were functionalized with zwitterionic sulfobetaine side chains with different degrees of substitution (DS) for the finishing of poly(ethylene terephthalate) (PET) and cotton fabrics in a water-based pad-dry-cure process. After washing with different surfactants, a stable finish with total polymer add-ons of 0.2-0.5 wt% was achieved. The finished textiles efficiently inhibited the adhesion of proteins and bacteria to the surface even with a small DS as low as 20%. Textiles finished with polymers with a low DS also showed significant antibacterial activity, most notably against Staphylococcus aureus. Accordingly, textile finishes with either pure antiadhesive (DS > 50%) or combined antiadhesive and antibacterial properties (DS = 20-50%) are accessible using this approach. © The Royal Society of Chemistry.
    view abstract10.1039/C8RA09975H
  • Polymorphism of hydrogen-bonded star mesogens-a combinatorial DFT-D and FT-IR spectroscopy study
    Pfletscher, M. and Wysoglad, J. and Gutmann, J.S. and Giese, M.
    RSC Advances 9 (2019)
    A comprehensive study combining detailed computational analyses with temperature-variable FT-IR experiments was performed in order to elucidate the structure of the hydrogen-bonded liquid crystals based on phloroglucinol and azopyridine in their mesophase. Conformational analysis revealed three relevant conformers: star, λ- and E-shape. The results demonstrate an entropy-driven unfolding mechanism of the assembly. The stability of the conformers is given by intermolecular π-π and dispersion interactions of the azopyridine side chains. Correlating the calculated vibrational frequency with experimental FT-IR spectra suggests a λ-folded conformation of the assemblies as the predominant species in the mesophase. © 2019 The Royal Society of Chemistry.
    view abstract10.1039/c8ra09458f
  • Procedures for the characterization of wettability and surface free energy of textiles - use, abuse, misuse and proper use: A critical review
    Bahners, T. and Gutmann, J.S.
    Reviews of Adhesion and Adhesives 7 (2019)
    Functional finishing and surface functionalization play an ever-increasing role in the design of functional textiles for, e.g., technical and industrial applications. Surface treatments impart chemical modifications to the fiber surface that affect the surface free energy, either with the aim to alter the wetting behavior, or to influence related properties, such as adhesion, surface conductivity, adsorption of proteins, etc. On planar substrates, the measurement of contact angles of specific liquids and making use of formalisms such as the Owens-Wendt is a common approach to determine the surface free energy (SFE) and thus characterize the effects of surface treatments. This direct approach is often uncritically applied to porous and textured samples such as textiles, too. One cannot overemphasize, though, how the complex geometry of a textile fabric, defined by the topography of the fiber, construction of the yarn, and construction of the fabric, affects its wetting behavior. Spreading on a rough surface, penetration, and capillary-driven liquid motion in the multi-porous yarn system will occur at the same time. Accordingly, the observed contact angle will in most cases be neither static nor a reliable measure of fiber SFE. Therefore, a critical consideration of any analytical method for SFE or wettability characterization is of utmost importance. The scope of the present critical analysis is to compare and discuss the pros and cons of various methods commonly used in textile research. It can be summarized that contact angles can be useful for comparative measurements on hydrophobic samples, while the established drop penetration tests characterize the effects of fabric finishing, fiber surface modifications, etc. with limited quantitative discrimination. The single fiber micro-Wilhelmy test is in theory a reliable method to obtain contact angles on fibers but has experimental limitations. More recent concepts based on the Washburn or IGC analysis of more or less defined fiber bundles appear to be promising approaches to deliver reliable information on SFE and also on adhesion. © 2019 Scrivener Publishing LLC.
    view abstract10.7569/RAA.2019.097310
  • Carbodiimide-mediated immobilization of acidic biomolecules on reversed-charge zwitterionic sensor chip surfaces
    Risse, F. and Gedig, E.T. and Gutmann, J.S.
    Analytical and Bioanalytical Chemistry 410 (2018)
    The carbodiimide-mediated amine coupling of protein ligands to sensor chips coated with anionic polycarboxylate hydrogels, such as carboxymethyl dextran, is the predominant covalent immobilization procedure utilized in optical biosensors, namely surface plasmon resonance (SPR) biosensors. Usually, electrostatic interactions at a slightly acidic pH and low ionic strength are employed to efficiently accumulate neutral and basic ligands on the chip surface, which are then covalently coupled by surface-bound active N-hydroxysuccinimide (NHS) esters. Unfortunately, this approach is not suitable for acidic proteins or other ligands with low isoelectric points (IEPs), such as nucleic acids, because the charge density of the polycarboxylates is greatly reduced at acidic pH or because electrostatic attraction cannot be achieved. To overcome these drawbacks, we have established a charge-reversal approach that allows the preconcentration of acidic proteins above their IEPs. A precisely controlled amount of tertiary amines is applied to reverse the previous anionic surface charge while maintaining carbodiimide compatibility with future protein immobilization. The mechanism of this reversed-charge immobilization approach was demonstrated employing protein A as a model protein and using attenuated total reflectance Fourier transform infrared spectroscopy, dynamic contact angle measurements, colorimetric quantification, and SPR analysis to characterize surface derivatization. Furthermore, even though it had previously proven impossible to preconcentrate DNA electrostatically and to covalently couple it to polyanionic chip surfaces, we demonstrated that our approach allowed DNA to be preconcentrated and immobilized in good yields. [Figure not available: see fulltext.]. © 2018, Springer-Verlag GmbH Germany, part of Springer Nature.
    view abstract10.1007/s00216-018-1048-0
  • Conformational study of melamine crosslinkers and spectroscopical comparison of HMMM molecules by practical measurements and quantum chemical calculations
    Wysoglad, J. and Ehlers, J.-E. and Lewe, T. and Dornbusch, M. and Gutmann, J.S.
    Journal of Molecular Structure 1166 (2018)
    To understand and improve network formation processes and performance properties makes structural molecular studies critically important for the coil-coating industry. Crosslinking agents such as hexamethoxymethylmelamine (HMMM) or less methylated derivatives, e.g. methoxymethylmelamine (MMM), are often added to industrial coating formulations. For molecules with considerably fewer atoms and accordingly less rotational freedom (such as MMM) it is readily accessible to identify principal conformations. Thus, an MMM conformer study is straightforward and serves as orientation concerning HMMM conformer studies. For HMMM molecules an extensive computation method was developed to investigate the conformational distribution average and probably most likely molecular structures. Using the density functional theory (DFT) B3LYP-D3BJ method with Dunning's correlation basis set, calculations were performed to investigate the three-dimensional structural geometries of HMMM (basis set cc-pVDZ) and MMM (basis set cc-pVTZ). Beginning with 1500 conformations for HMMM and using various cut-off filters we focused on final residual 22 conformers for solvent phase calculations and 16 conformers for gas phase calculations. To the best of our knowledge, this is the first time that chemical properties for melamine crosslinkers were presented under consideration of conformational population distribution. Thus, computations of fully optimized structural geometries, energies and vibrational states indicate that preferred structural alignments for the methoxymethyl (MM) group in melamine molecules exist. Nevertheless, we suppose that as a matter of principle the MM group of MMM molecules can easily perform rotations by itself and all conformational structure geometries of MMM will exist. Concerning the MM groups position compared to triazine plane HMMM molecules have two main configurations,”3up-3down” and “4up-2down”, as dominant conformer species. Computations of weighted and averaged IR and Raman spectra of final conformations for HMMM monomers, dimers and trimers at ambient temperature are novel and in good agreement with experiment. Prediction of a final UV–Vis spectrum of top ten Boltzmann-weight and averaged monomeric HMMM conformers is in perfect agreement with practical measurement of commercially available HMMM. © 2018 Elsevier B.V.
    view abstract10.1016/j.molstruc.2018.04.069
  • Corrigendum to "Simplifying cantilever sensors: Segmental analysis, a way to multiply your output" [Sens. Actuators B 177 (2013) 1142-1148]
    Ochsmann, J.W. and Cavaliere, A. and Lenz, S. and Raiteri, R. and Gutmann, J.S. and Berger, R.
    Sensors and Actuators, B: Chemical (2018)
    view abstract10.1016/j.snb.2017.12.113
  • Corrosion analysis of decorative microporous chromium plating systems in concentrated aqueous electrolytes
    Langer, C. and Wendland, W. and Honold, K. and Schmidt, L. and Gutmann, J.S. and Dornbusch, M.
    Engineering Failure Analysis 91 (2018)
    The corrosion behavior of microporous chromium plating systems in concentrated aqueous electrolytes was studied to describe the so-called Russian-mud corrosion of microporous chromium plating systems from decorative car parts. Corrosive stressed chromium plating systems from Russia were analyzed with scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDX) to characterize the specific corrosion mechanism. The electrochemical corrosion behavior was evaluated by potentiodynamic polarization curves, zero resistance ammetry and electrochemical impedance spectroscopy (EIS). The obtained results show two different corrosion mechanisms, dissolving of the chromium plating and undercutting of the chromium plating at specific conditions. © 2018 Elsevier Ltd
    view abstract10.1016/j.engfailanal.2018.04.031
  • Deformation of Mesoporous Titania Nanostructures in Contact with D2O Vapor
    Song, L. and Rawolle, M. and Hohn, N. and Gutmann, J.S. and Frielinghaus, H. and Müller-Buschbaum, P.
    Small 14 (2018)
    For many applications, mesoporous titania nanostructures are exposed to water or need to be backfilled via infiltration with an aqueous solution, which can cause deformations of the nanostructure by capillary forces. In this work, the degree of deformation caused by water infiltration in two types of mesoporous, nanostructured titania films exposed to water vapor is compared. The different types of nanostructured titania films are prepared via a polymer template assisted sol–gel synthesis in conjunction with a polymer-template removal at high-temperatures under ambient conditions versus nitrogen atmosphere. Information about surface and inner morphology is extracted by scanning electron microscopy and grazing incidence small-angle neutron scattering (GISANS) measurements, respectively. Furthermore, complementary information on thin film composition and porosity are probed via X-ray reflectivity. The backfilling induced deformation of near surface structures and structures inside the mesoporous titania films is determined by GISANS before and after D2O infiltration. The respective atmosphere used for template removal influences the details of the titania nanostructure and strongly impacts the degree of water induced deformation. Drying of the films shows reversibility of the deformation. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
    view abstract10.1002/smll.201801461
  • Improvement of fibre–matrix adhesion in cellulose/polyolefin composite materials by means of photo-chemical fibre surface modification
    Bahners, T. and Kelch, M. and Gebert, B. and Osorio Barajas, X.L. and Schmidt, T.C. and Gutmann, J.S. and Müssig, J.
    Cellulose 25 (2018)
    The mechanical performance of composites made from viscose fibre reinforcement fabrics and PP matrix polymers could be enhanced by photo-chemical surface modification of the viscose fibres. The surface modification was achieved by deposition of UV-polymerized organic thin layers using pentaerythritol triacrylate or diallylphthalate as monomers. The main effects of the photo-chemical modification refer to a decrease in wettability of the highly hydrophilic and water adsorbing viscose fibres and an increase in their affinity towards non-polar substances. Both effects were found to yield an increase in fibre–matrix adhesion and interfacial shear strength, resulting in better impact and tensile properties compared to untreated samples. The experimental composites were slightly inferior with regard to fibre–matrix adhesion and IFSS than established systems using modified matrix polymers such as the maleic anhydride modified PP, but exhibited similar or even improved properties in view of tensile strength and impact behaviour. The latter indicates superior energy transfer by the thin organic layers forming the fibre–matrix interface. Based on these observations, the studied concept of photo-polymerized inter-layers between fibre and matrix can be understood as a biomimetic concept mimicking the graded transitions of natural structures. © 2018, Springer Science+Business Media B.V., part of Springer Nature.
    view abstract10.1007/s10570-018-1724-4
  • On the potential of using dual-function hydrogels for brackish water desalination
    Ali, W. and Gebert, B. and Altinpinar, S. and Mayer-Gall, T. and Ulbricht, M. and Gutmann, J.S. and Graf, K.
    Polymers 10 (2018)
    Although current desalination technologies are mature enough and advanced, the shortage of freshwater is still considered as one of the most pressing global issues. Therefore, there is a strong incentive to explore and investigate new potential methods with low energy consumption. We have previously reported that reversible thermally induced sorption/desorption process using polymeric hydrogels hold promise for water desalination with further development. In order to develop a more effective hydrogels architecture, polyelectrolyte moieties were introduced in this work as pendent chains and a thermally responsive polymer as network backbone using reversible addition-fragmentation chain transfer (RAFT) polymerisation. The ability of the comb-type polymeric hydrogels to desalinate water was evaluated. These hydrogels were proved to absorb water with low salinity from brine solution of 2 g L-1 NaCl and release the absorbed water at relatively low temperature conditions of 50 °C. The fraction of the grafted polyacrylic acid and the comb-chain length were varied to understand their influence on the swelling/deswelling behaviour for these hydrogels. The ionic fraction in the hydrogels and the resulting hydrophilic/hydrophobic balance are crucial for the proposed desalination process. In contrast, the comb-chain length impacted the swelling behaviour of hydrogels but showed relatively little influence on the dewatering process. © 2018 by the authors.
    view abstract10.3390/polym10060567
  • Patterned functionalization of textiles using uv-based techniques for surface modification - patterned wetting behavior
    Bahners, T. and Mayer-Gall, T. and Mölter-Siemens, W. and Gutmann, J.S.
    Advances in Contact Angle, Wettablility and Adhesion 3 (2018)
    A long-standing goal of surface functionalization of textile fabrics has been to impart a (super-)hydrophobic or oleophobic character. While the majority of reported solutions have aimed at a homogeneous finish with identical wetting behavior of the whole fabric area on front and back faces, patterned or graded wetting properties have come into focus only in recent years. This sort of patterned processing opens avenues to functionalities far beyond conventional textile finishing. Interesting wetting effects of, e.g., plant and animal surfaces can thus be mimicked and transferred to textile substrates. In this context, photon-based processes for surface modification such as photo-grafting, photo-polymerization, or laser-induced surface roughening are highly interesting, as their effects can easily be confined to chosen areas by, e.g., masking or scanning. In case of porous substrates such as textile fabrics, patterning can also refer to creating differing properties of inner and outer surfaces simply based on the shading of UV light by strongly absorbing fibers, thus preventing modification of pores and capillaries. Various examples of patterned wetting behavior created by photonic processes are presented here in order to indicate the potential of the concept. © 2018 John Wiley & Sons Ltd. Published 2018 by John Wiley & Sons Ltd.
    view abstract10.1002/9781119459996.ch6
  • Polymer Diffusion in the Interphase between Surface and Solution
    Weger, L. and Weidmann, M. and Ali, W. and Hildebrandt, M. and Gutmann, J.S. and Hoffmann-Jacobsen, K.
    Langmuir 34 (2018)
    Total internal reflection fluorescence correlation spectroscopy (TIR-FCS) is applied to study the self-diffusion of poly(ethylene glycol) solutions in the presence of weakly attractive interfaces. Glass coverslips modified with aminopropyl- and propyl-terminated silanes are used to study the influence of solid surfaces on polymer diffusion. A model of three phases of polymer diffusion allows to describe the experimental fluorescence autocorrelation functions. Besides the two-dimensional diffusion of adsorbed polymer on the substrate and three-dimensional free diffusion in bulk solution, a third diffusion time scale is observed with intermediate diffusion times. This retarded three-dimensional diffusion in the solution is assigned to the long-range effects of solid surfaces on diffusional dynamics of polymers. The respective diffusion constants show Rouse scaling (D ∼ N-1), indicating a screening of hydrodynamic interactions by the presence of the surface. Hence, the presented TIR-FCS method proves to be a valuable tool to investigate the effect of surfaces on polymer diffusion beyond the first adsorbed polymer layer on the 100 nm length scale. © 2018 American Chemical Society.
    view abstract10.1021/acs.langmuir.8b00660
  • UV-light assisted patterned metallization of textile fabrics
    Bahners, T. and Gebert, B. and Prager, A. and Hartmann, N. and Hagemann, U. and Gutmann, J.S.
    Applied Surface Science 436 (2018)
    A UV-assisted process allows full-faced or local deposition of silver domains on textiles made of natural as well as synthetic fibers, which act as nuclei for subsequent galvanic metallization. SEM and XPS analyses indicate that the process generates particulate depositions – particles, aggregates – of elementary silver. Masking the UV irradiation confines silver deposition strictly to the exposed areas thus allowing patterning. Adhesion of the deposited silver is high on the studied natural fiber cotton and polyamide fibers. Adhesion on smooth and chemically inert synthethic fibers such as, e.g., poly(ethylene terephthalate) or para- and meta-aramids could be enhanced by finishing with poly(vinylamine) thus providing complex-forming amino groups. Although the process does not deposit a closed, electrically conducting layer, all studied samples could be metallized by galvanization. The resulting metal coatings exhibit high conductivity and wash stability. Following a patterned silver deposition, the subsequent galvanic metallization produced conductive patterns of identical geometry thus opening an avenue towards printed circuits on textile fabrics. © 2017 Elsevier B.V.
    view abstract10.1016/j.apsusc.2017.12.119
  • Gradual modification of ITO particle's crystal structure and optical properties by pulsed UV laser irradiation in a free liquid jet
    Lau, M. and Straube, T. and Aggarwal, A.V. and Hagemann, U. and De Oliveira Viestel, B. and Hartmann, N. and Textor, T. and Lutz, H. and Gutmann, J.S. and Barcikowski, S.
    Dalton Transactions 46 (2017)
    Indium tin oxide (ITO) particle coatings are known for high transparency in the visible, good conductive properties and near-infrared absorption. These properties depend on ITO particle's stoichiometric composition, defects and size. Here we present a method to gradually change ITO particle's optical properties by a simple and controlled laser irradiation process. The defined irradiation process and controlled energy dose input allows one to engineer the absorption and transmission of coatings made from these particles. We investigate the role of the surrounding solvent, influence of laser fluence and the specific energy dose targeting modification of the ITO particle's morphology and chemistry by stepwise laser irradiation in a free liquid jet. TEM, SEM, EDX, XPS, XRD and Raman are used to elucidate the structural, morphological and chemical changes of the laser-induced ITO particles. On the basis of these results the observed modification of the optical properties is tentatively attributed to chemical changes, e.g. laser-induced defects or partial reduction. © 2017 The Royal Society of Chemistry.
    view abstract10.1039/c7dt00010c
  • Laser-induced surface activation of biocomposites for electroless metallization
    Rytlewski, P. and Bahners, T. and Polewski, F. and Gebert, B. and Gutmann, J.S. and Hartmann, N. and Hagemann, U. and Moraczewski, K.
    Surface and Coatings Technology 311 (2017)
    In this work biocomposites containing polylactide (PLA), polycaprolactone (PCL), copper(II) oxide and copper acetylacetonate were manufactured by an extrusion process. The extruded composites differed with respect to the PLA/PCL ratio whereas the content of mixed copper(II) oxide and copper acetylacetonate powders was held constant at 20 wt%. The main aims for the addition of PCL was to increase impact strength resistance, improve surface catalytic properties and reduce the temperature of extrusion, thus limiting degradation effects initiated by copper acetylacetonate. The composite samples were irradiated with an ArF excimer laser varying the number of laser pulses and then metalized by electroless plating. Based on optical microscopy, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS) measurements, it was found that (i) PCL was dispersed in the form of droplets in all volume of PLA, (ii) the copper compounds were preferably located in the dispersed PCL phase, and (iii) composites with higher PCL content were more effectively metalized. © 2016 Elsevier B.V.
    view abstract10.1016/j.surfcoat.2016.12.048
  • Poly (glycerol sebacate)-poly (ε-caprolactone) blend nanofibrous scaffold as intrinsic bio- and immunocompatible system for corneal repair
    Salehi, S. and Czugala, M. and Stafiej, P. and Fathi, M. and Bahners, T. and Gutmann, J.S. and Singer, B.B. and Fuchsluger, T.A.
    Acta Biomaterialia 50 (2017)
    A major challenge in corneal tissue engineering and lamellar corneal transplantation is to develop synthetic scaffolds able to simulate the optical and mechanical properties of the native cornea. As a carrier, the graft scaffolds should provide the basis for anchorage, repair and regeneration. Although quite a number of scaffolds have been engineered to date, they have not been able to simultaneously recapitulate chemical, mechanical, and structural properties of the corneal extracellular matrix (ECM). Here, we examined different compositions of elastomeric biodegradable poly (glycerol sebacate) (PGS)-poly (ε-caprolactone) (PCL) nanofibrous scaffolds with respect to their cyto- and immunocompatibility. These scaffolds were semi-transparent with well-defined mechanical properties and direct positive effects on viability of human corneal endothelial cells (HCEC) and human conjunctival epithelial cells (HCjEC). Moreover, within 3. days HCEC established monolayers with the hexagonal morphology typical for this cell type. All PGS-PCL mixtures analyzed did not trigger effects in granulocytes, naïve and activated peripheral blood mononuclear cells (PBMCs). However, scaffolds with a higher content of PGS-PCL ratio showed the best cell organization, cyto- and immunocompatibility. Subsequently, this PGS-PCL composition could be used for further development of clinical constructs to support corneal tissue repair. Statement of Significance: In corneal tissue engineering a major challenge is the development of synthetic scaffolds with similar properties to native cornea. In our recent works, we introduced the biodegradable, polymeric nanofibrous scaffolds with similar optical and mechanical properties for corneal regeneration and here we examined the cyto- and immunocompatibility of biodegradable nanofibrous scaffolds in contact to white blood cells. Directing the alignment of human corneal cells by nanofibrous scaffolds and high viability of cells was detected by forming of endothelium monolayer with hexagonal morphology on the nanofibrous scaffold. In addition, our results for the first time show that these nanofibrous scaffolds did not trigger effects in white blood cells. These results highlight the considerable translational potential of the nanofibrous scaffolds to clinical applications. © 2017 Acta Materialia Inc.
    view abstract10.1016/j.actbio.2017.01.013
  • Polyol synthesized aluminum doped zinc oxide nanoparticles - Influence of the hydration ratio on crystal growth, dopant incorporation and electrical properties
    Straube, T. and Linders, J. and Mayer-Gall, T. and Textor, T. and Mayer, C. and Gutmann, J.S.
    Materials Today: Proceedings 4 (2017)
    The wet chemical deposition of solution processed transparent conducting oxides (TCO) provides an alternative low cost and economical deposition technique to realize large-areas of conducting films. Since the price for the most common TCO Indium Tin Oxide rises enormously, Aluminum Zinc Oxide (AZO) as alternative TCO reaches more and more interest. The optoelectronical properties of nanoparticle coatings strongly depend beneath the porosity of the coating on the shape and size of the used particles. By using bigger or rod-shaped particles it is possible to minimize the amount of grain boundaries resulting in an improvement of the electrical properties, whereas particles bigger than 100 nm should not be used if highly transparent coatings are necessary as these big particles scatter the visible light and lower the transmittance of the coatings. In this work we present a simple method to synthesize AZO particles with different shape and size, but comparable electronical properties. We use a simple, well reproducible polyol method for synthesis and influence the shape and size of the particles by adding different amounts of water to the precursor solution. We can show that the addition of aluminum as dopant strongly hinders the crystal growth but the addition of water counteracts this, so that both, spherical and rod-shaped particles can be obtained. © 2017 Elsevier Ltd.
    view abstract10.1016/j.matpr.2017.09.196
  • Polyvinylamine-coated polyester fibers as a carrier matrix for the immobilization of peroxidases
    Kiehl, K. and Opwis, K. and Gutmann, J.S.
    Engineering in Life Sciences 17 (2017)
    Biocatalytic transformations that employ immobilized enzymes become increasingly important for industrial applications. Synthetic or natural textile fiber materials such as polyester, polyamide or viscose are support materials that are comparatively inexpensive. Contrary to traditional support materials, their flexibility enables their use in reactors of any geometry and a fast and residue-free removal from batch reactors. In this study a permanently immobilized peroxidase (Baylase®) has been investigated on polyester felt as a solid support as a new heterogeneous catalyst system. The polyester felt was functionalized by coating with polyvinylamine and subsequent activation with glutaraldehyde as a crosslinking agent. The enzyme load on the textile surface, the activity of the immobilized protein after repeated use as well as the storage stability was evaluated. Scanning electron micrographs and UV Vis spectroscopy made it possible to verify the enzyme immobilization on the textile surface. Furthermore, the load of immobilized peroxidase was determined by ICP OE spectrometry to be 9-12 mg per gram of textile. The activity of immobilized Baylase® remained high over 35 reaction cycles and a storage period of 8 weeks. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
    view abstract10.1002/elsc.201600170
  • A modular approach towards functional supramolecular aggregates-subtle structural differences inducing liquid crystallinity
    Pfletscher, M. and Wölper, C. and Gutmann, J.S. and Mezger, M. and Giese, M.
    Chemical Communications 52 (2016)
    Herein we report an efficient modular approach to supramolecular functional materials. Hierarchical self-assembly of azopyridine derivatives and hydrogen-bond donors yielded discotic assemblies. Subtle differences in the core units introduced mesomorphic behaviour and fast photo-response of the liquid crystals based on phloroglucinol. The presented results prove the benefits of a modular methodology towards highly responsive materials with tailor-made properties. © 2016 The Royal Society of Chemistry.
    view abstract10.1039/c6cc03966a
  • Bound rubber morphology and loss tangent properties of carbon-black-filled rubber compounds
    Gabriel, D. and Karbach, A. and Drechsler, D. and Gutmann, J. and Graf, K. and Kheirandish, S.
    Colloid and Polymer Science 294 (2016)
    The bound rubber phenomenon of carbon-black-filled rubber compounds, which is still an intensively discussed subject, is visualized in this research as a stable nanoscale interphase. Using the novel amplitude and phase-modified atomic force microscope technique, a viscoelastic mapping mode, it becomes possible to quantify mechanical loss tangent properties that are defined as the ratio of loss modulus G″ to storage modulus G′. Imaging loss tangent enables the observation of separated energy dissipation of single constituents within a blend system as well as bound rubber dimensions. Determined with the conventional quantification of insoluble rubber, the amount of bound rubber is correlated with values from the analytical evaluation of loss tangent images. Comparing the loss tangent images and histograms to dynamic mechanical analyses allows the characterization of each single component. On the base of the time-temperature superposition principle, bound rubber dimensions and mechanical properties of filled compounds can be optimized. © 2015, Springer-Verlag Berlin Heidelberg.
    view abstract10.1007/s00396-015-3802-6
  • Employing ionic liquids to deposit cellulose on PET fibers
    Textor, T. and Derksen, L. and Gutmann, J.S.
    Carbohydrate Polymers 146 (2016)
    Several ionic liquids are excellent solvents for cellulose. Starting from that finishing of PET fabrics with cellulose dissolved in ionic liquids like 1-ethyl-3-methyl imidazolium acetate, diethylphosphate and chloride, or the chloride of butyl-methyl imidazolium has been investigated. Finishing has been carried out from solutions of different concentrations, using microcrystalline cellulose or cotton and by employing different cross-linkers. Viscosity of solutions has been investigated for different ionic liquids, concentrations, cellulose sources, linkers and temperatures. Since ionic liquids exhibit no vapor pressure, simple pad-dry-cure processes are excluded. Before drying the ionic liquid has to be removed by a rinsing step. Accordingly rinsing with fresh ionic liquid followed by water or the direct rinsing with water have been tested. The amount of cellulose deposited has been investigated by gravimetry, zinc chloride iodine test as well as reactive dyeing. Results concerning wettability, water up-take, surface resistance, wear-resistance or washing stability are presented. © 2016 Elsevier Ltd. All rights reserved.
    view abstract10.1016/j.carbpol.2016.03.053
  • Flame retardants based on amino silanes and phenylphosphonic acid
    Kappes, R.S. and Urbainczyk, T. and Artz, U. and Textor, T. and Gutmann, J.S.
    Polymer Degradation and Stability 129 (2016)
    The sol-gel approach offers a new class of flame retardants with a high potential for textile applications. Pure inorganic sol-gel systems do, however, typically not provide an effect sufficient for a self-extinguishing behavior on its own. We therefore employed compounds with nitrogen and phosphorous containing groups. Especially the combination of compounds with both elements, using the synergism, is promising for the aim to find well-applicable, environmental friendly, halogen-free flame retardants. In our approach, the sol-gel network ensured on the one hand the link to the textile as non-flammable binder. On the other hand, the sol-gel-based networks modified with functional groups containing nitrogen groups provided flame retardancy. In this way, a flame retardant finishing for textiles could be obtained by simple finishing techniques as, e.g., padding. Besides a characterization with various flame tests (e.g., according to EN ISO 15025 - protective clothing), we used a combination of cone calorimetry, thermogravimetry coupled with infrared spectroscopy analysis and scanning electron microscopy to analyze the mechanism of flame retardancy. Thus, we could show that the main mechanism is based on the formation of a protection layer. This work provides a model system for sol-gel-based flame retardants and has the potential to show the principle feasibility of the sol-gel approach in flame retardancy of textiles. It therefore lays the groundwork for tailoring sol-gel layers from newly synthesized sol-gel precursors containing nitrogen and phosphorous groups. © 2016 Elsevier Ltd. All rights reserved.
    view abstract10.1016/j.polymdegradstab.2016.04.012
  • Immobilization of peroxidases on textile carrier materials and their use in bleaching processes
    Opwis, K. and Kiehl, K. and Gutmann, J.S.
    Chemical Engineering Transactions 49 (2016)
    The economical use of often high-priced enzymes in chemical synthesis can be improved by the immobilization of the catalyst on a suitable carrier. Particularly some synthetic or natural textile fiber materials such as polyester, polyamide or viscose are well-suited carrier materials, which are comparatively inexpensive. The flexibility of the textile media allows the use in reactors of any geometry and a fast and residue-free removal after the end of each reaction. Enzymatically catalyzed reactions combine a number of advantages compared to conventional chemical processes. For instance enzymes can be used at moderate temperatures, generally in the pH ranges close to neutral and stay unchanged after the reaction. Therefore, often very small quantities are enough for a sufficiently high implementation rate. Other advantages are their high substrate selectivity, their biodegradability and their mostly safe and easy handling. Especially in food industries bleaching processes with chemical additives such as benzoyl peroxide could be replaced by innovative methods of 'white biotechnology'. Here, we present an efficient method for the permanent immobilization of peroxidases on modified textile carrier materials and their use in the gentle enzymatic degradation of food colors (e.g. norbixin) in whey from cheese dairy. The textile-fixed peroxidase shows a distinct bio-catalytc activity over at least 15 reactions cycles. In addition, the fiber-fixed enzyme is able to bleach industrial whey completely. © 2016, AIDIC Servizi S.r.l.
    view abstract10.3303/CET1649012
  • Preparation of a Textile-Based Dye-Sensitized Solar Cell
    Opwis, K. and Gutmann, J.S. and Lagunas Alonso, A.R. and Rodriguez Henche, M.J. and Ezquer Mayo, M. and Breuil, F. and Leonardi, E. and Sorbello, L.
    International Journal of Photoenergy 2016 (2016)
    Solar energy conversion is an object of continuous research, focusing on improving the energy efficiency as well as the structure of photovoltaic cells. With efficiencies continuously increasing, state-of-the-art PV cells offer a good solution to harvest solar energy. However, they are still lacking the flexibility and conformability to be integrated into common objects or clothing. Moreover, many sun-exposed surface areas are textile-based such as garments, tents, truck coverings, boat sails, and home or outdoor textiles. Here, we present a new textile-based dye-sensitized solar cell (DSC) which takes advantage from the properties inherent to fabrics: flexibility, low weight, and mechanical robustness. Due to the necessary thermostability during manufacturing, our DSC design is based on heat-resistant glass-fiber fabrics. After applying all needed layers, the overall structure was covered by a transparent and simultaneously conductive protective film. The light and still flexible large-area devices (up to 6 cm2 per individual unit) are working with efficiencies up to 1.8% at 1/5 of the sun. Stability tests assure no loss of photovoltaic activity over a period of at least seven weeks. Therefore, our technology has paved the way for a new generation of flexible photovoltaic devices, which can be used for the generation of power in the mentioned applications as well as in modern textile architecture. © 2016 Klaus Opwis et al.
    view abstract10.1155/2016/3796074
  • Textile Catalysts - An unconventional approach towards heterogeneous catalysis
    Mayer-Gall, T. and Lee, J.-W. and Opwis, K. and List, B. and Gutmann, J.S.
    ChemCatChem 8 (2016)
    Textile catalysts are a new approach utilizing immobilization of different classes of catalysts onto textile materials such as polyethylene terephthalate and polyamide. Robust, inexpensive fibrous materials are chosen because they are available in many variations. By a photochemical approach a series of different supported organocatalysts (organotextile catalysts) has been prepared, showing high catalytic activity and good reusability. The aim of this concept article is to present the scope, limits and open questions of our innovative approach. The working principle of the immobilization and its control parameters will be explained and the scope of useable catalysts is shown. Therefore we will show the significant influence of the anchoring group on loading and more importantly on catalyst activity. This concept is also applicable to organometallic catalysts and enzymes. Understanding the different phenomena allows us to develop "textile catalysts" as a new powerful tool for heterogeneous catalysis. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
    view abstract10.1002/cctc.201501252
  • Using bulk properties of uv-polymerized thin layers for fiber modification
    Bahners, T. and Gutmann, J.S.
    Surface Innovations 4 (2016)
    The surface properties of fibers can be regarded as instrumental toward innovative functional textiles as applied in many high-end industries. Accordingly, not only the modification of surface chemistry, but also of the physical and morphological properties is an important objective in modern materials science and technology. Besides other powerful chemical and physical techniques, UV-induced graft copolymerization and photopolymerization are interesting ways to improve or introduce surface functionalities of the fiber. While the majority of reported work focused on the surface of the deposited thin layer itself and its potential effect on – for example, wettability, adhesion, protein adsorption and microbial activity, this paper reviews earlier studies by the authors which were devoted to bulk properties of these thin, less than 500-nm thick layers and the resulting effect on fiber properties. One major factor is the high and controllable cross-linking of polymerized layers, which affects mechanical, thermal and chemical stability. This results in interesting applications as thin barrier coating in view of improved fiber stability in critical environments and stress conditions, examples of which are reported in this paper. A recent observation is the effect of the controlled cross-linking on the mobility of monomers and electrical charges in the thin layer, which could open an avenue toward thin-layer capacitors and energy storage on textiles. © ICE Publishing: All rights reserved.
    view abstract10.1680/jsuin.15.00021
  • Application of hybrid blocking layers in solid-state dye-sensitized solar cells
    Lellig, P. and Meister, M. and Ochsmann, J.W. and Niedermeier, M.A. and Rawolle, M. and Laquai, F. and Müller-Buschbaum, P. and Gutmann, J.S.
    SpringerPlus 4 (2015)
    A hybrid blocking layer consisting of a conducting TiO<inf>2</inf> network embedded in a ceramic matrix is implemented in a solid-state dye-sensitized solar cell. This novel type of blocking layer is thinner than the classical blocking layer films as shown with SEM and XRR measurements, and thereby the conductivity of the hybrid film is increased by 110%. A percolating TiO<inf>2</inf> network, proven by TEM/ESI and GISAXS measurements, allows for the charge transport. Although being thinner, the hybrid film completely separates the rough electrode material from the hole-transport medium in solar cells to avoid the recombination of charge carriers at this interface. In total, the power conversion efficiency of solar cells is improved: the application in photovoltaics shows that the efficiency of devices with the hybrid blocking layer is increased by 6% compared to identical solar cells employing the conventional blocking layer. © 2015, Lellig et al.
    view abstract10.1186/s40064-015-1140-2
  • Design of Thermally Responsive Polymeric Hydrogels for Brackish Water Desalination: Effect of Architecture on Swelling, Deswelling, and Salt Rejection
    Ali, W. and Gebert, B. and Hennecke, T. and Graf, K. and Ulbricht, M. and Gutmann, J.S.
    ACS Applied Materials and Interfaces 7 (2015)
    In this work, we explore the ability of utilizing hydrogels synthesized from a temperature-sensitive polymer and a polyelectrolyte to desalinate salt water by means of reversible thermally induced absorption and desorption. Thus, the influence of the macromolecular architecture on the swelling/deswelling behavior for such hydrogels was investigated by tailor-made network structures. To this end, a series of chemically cross-linked polymeric hydrogels were synthesized via free radical-initiated copolymerization of sodium acrylate (SA) with the thermoresponsive comonomer N-isopropylacrylamide (NIPAAm) by realizing different structural types. In particular, two different polyNIPAAm macromonomers, either with one acrylate function at the chain end or with additional acrylate functions as side groups were synthesized by controlled polymerization and subsequent polymer-analogous reaction and then used as building blocks. The rheological behaviors of hydrogels and their estimated mesh sizes are discussed. The performance of the hydrogels in terms of swelling and deswelling in both deionized water (DI) and brackish water (2 g/L NaCl) was measured as a function of cross-linking degree and particle size. The salt content could be reduced by 23% in one cycle by using the best performing material. (Figure Presented). © 2015 American Chemical Society.
    view abstract10.1021/acsami.5b03878
  • Distortion of Ultrathin Photocleavable Block Copolymer Films during Photocleavage and Nanopore Formation
    Altinpinar, S. and Zhao, H. and Ali, W. and Kappes, R.S. and Schuchardt, P. and Salehi, S. and Santoro, G. and Theato, P. and Roth, S.V. and Gutmann, J.S.
    Langmuir 31 (2015)
    Highly ordered block copolymer thin films have been studied extensively during the last years because they afford versatile self-assembled morphologies via a bottom-up approach. They promise to be used in applications such as polymeric membranes or templates for nanostructured materials. Among the block copolymer structures, perpendicular cylinders have received strong attention due to their ability to fabricate highly ordered nanopores and nanowires. Nanopores can be created from a thin block copolymer film upon the removal of one block by selective etching or by dissolution of one polymer block. Here we demonstrate the utilization of polystyrene-block-poly(ethylene oxide) diblock copolymer (PS-hν-PEO) with an ortho-nitrobenzyl ester (ONB) as the photocleavable block-linker to create highly ordered thin films. Removal of the PEO block by choosing an appropriate solvent upon photocleavage is expected to yield arrays of nanopores decorated with functional groups, thus lending itself to adsorption or filtration uses. While the feasibility of this approach has been demonstrated, it is crucial to understand the influence of removal conditions (i.e., efficiency of photocleavage as well as best washing solvent) and to evaluate changes in the surface topology and inner structure upon photocleavage. To this end, the time dependence evolution of the surface morphology of block copolymer thin films was studied using grazing-incidence small-angle X-ray scattering (GISAXS) technique in combination with scanning probe microscopy. © 2015 American Chemical Society.
    view abstract10.1021/acs.langmuir.5b00750
  • Effect of sol-gel reaction time on the morphology transition in mesoporous titania/PS-b-PEO composite films
    Cheng, Y.-J. and Zhou, S. and Wolkenhauer, M. and Bumbu, G.-G. and Lenz, S. and Memesa, M. and Nett, S. and Emmerling, S. and Steffen, W. and Roth, S.V. and Gutmann, J.S.
    Science of Advanced Materials 7 (2015)
    A morphology transition from the coexistence of spherical and worm-like mesopores to highly branched wormlike mesopores within the titania thin films has been realized by varying the sol-gel reaction time from 51 minutes to 50 hours in the four-component templating system of PS-b-PEO, 1,4-dioxane, concentrated HCl, and Titanium tetraisopropoxide (TTIP). The impact of sol-gel reaction time on the local structure, long range lateral structure, and vertical structure of the as-prepared, calcined, and UV degraded thin films, and structure change in solution have been systematically investigated by scanning electron microscopy (SEM), atomic force microscopy (AFM), grazing incidence small angle X-ray scattering (GISAXS), X-ray reflectivity (XRR), and dynamic light scattering (DLS) respectively. With the sol-gel reaction time up to 5 hours, the morphology does not change significantly. Both spherical and worm-like domains exist, which are converted to spherical and worm-like mesopores after calcination or UV degradation due to the removal of the PS block. However, with the sol-gel reaction time extended to 25 and 50 hours, highly branched worm-like domains appear. As a result, highly porous mesopores are formed by calcination or UV degradation. The GISAXS results prove that the local structure change revealed by AFM and SEM is representative over macroscopic scale. X-ray reflectivity results indicate that an additional thin layer exists beneath the mesoporous titania layer due to the presence of large amount of worm-like domains. Dynamic light scattering (DLS) studies imply that the morphology transition is due to the fusion process of the worm-like micelles in solution. © 2015 by American Scientific Publishers.
    view abstract10.1166/sam.2015.1957
  • Everything clean? Transfer of DNA traces between textiles in the washtub
    Kamphausen, T. and Fandel, S. B. and Gutmann, J. S. and Bajanowski, T. and Poetsch, M.
    International Journal of Legal Medicine 129 (2015)
    Forensic genetic analysis of items possibly handled by a suspect or a victim is frequently inquired by the law enforcement authorities, since DNA left on touched objects can often be linked to an individual. Due to technical improvement, even poor traces, which seemed to be unsuitable for DNA analysis a few years ago, may be amplified successfully today. Yet, DNA can be transferred to a crime scene artificially or unintentionally without any primary contact between the individual and the object found at the crime scene, the so-called secondary transfer or indirect transfer in general. In this study, "secondary transfer" scenarios with cells and DNA of different origins under wet conditions were investigated. Transfer was simulated as either "washing by hand" in a washtub or as "machine laundry" in a washing machine. As expected, major differences were seen between blood stains and epithelial abrasions. DNA from blood donors could be detected clearly both on the donor and on the acceptor textile, regardless of washing method. Regarding epithelial abrasions, simulating worn clothes, after washing by hand, only little residual DNA was found, and partial profiles were displayed on the donor textile, while transfer to the acceptor textile occurred even less and not in noteworthy amount and quality. Single alleles could be found both on donor textiles and acceptor textiles after simulated machine wash, but no reliable DNA profile could be verified after laundry in machine. Therefore, a DNA transfer from one worn cloth (without blood stains) to another textile in the washing machine seems to be extremely unlikely.
    view abstract10.1007/s00414-015-1203-5
  • Permanent flame retardant finishing of textiles by allyl-functionalized polyphosphazenes
    Mayer-Gall, T. and Knittel, D. and Gutmann, J.S. and Opwis, K.
    ACS Applied Materials and Interfaces 7 (2015)
    Despite their excellent flame retardant properties, polyphosphazenes are currently not used as flame retardant agents for textile finishing, because a permanent fixation on the substrate surface has failed so far. Here, we present the successful synthesis and characterization of a noncombustible and foam-forming polyphosphazene derivative, that can be immobilized durably on cotton and different cotton/polyester blended fabrics using photoinduced grafting reactions. The flame retardant properties are improved, a higher limiting oxygen index is found, and the modified textiles pass several standardized flammability tests. As flame retardant mechanism a synergistic effect between the immobilized polyphosphazene and the textile substrate was observed. The polyphosphazene finishing induces an earlier decomposition of the material with a reduced mass loss in thermogravimetric analysis. The decomposition of cotton and polyester leads to the formation of phosphorus oxynitride, which forms a protecting barrier layer on the fiber surface. In addition, the permanence of the flame retardant finishing was proven by laundry and abrasion tests. © 2015 American Chemical Society.
    view abstract10.1021/acsami.5b02141
  • Phenothiazine-functionalized redox polymers for a new cathode-active material
    Golriz, A.A. and Suga, T. and Nishide, H. and Berger, R. and Gutmann, J.S.
    RSC Advances 5 (2015)
    Redox-active, phenothiazine-functionalized polymers were synthesized and employed as a promising cathode-active material (∼3.7 V vs. Li, 77 Ah kg-1) in a rechargeable battery. The longer spacer between phenothiazine and the polymer backbone contributed to the stability of the formed radical cations, resulting in decelerated self-discharge and improved cycle performance. This journal is © The Royal Society of Chemistry.
    view abstract10.1039/c4ra17107a
  • Polyvinylamine modified polyester fibers-innovative textiles for the removal of chromate from contaminated groundwater
    Mayer-Gall, T. and Opwis, K. and Gutmann, J.S.
    Journal of Materials Chemistry A 3 (2015)
    The soil and groundwater of many old industrial areas are polluted by different environmental hazards. Because of their high toxicity and carcinogenic potential, chromate contaminations are especially problematic and a complete cleanup of such areas is necessary to avoid fatal environmental and sanitary impacts. Conventionally, decontamination is carried out by the removal of the soil and a long-term filtration of groundwater with various chromate-adsorbing materials over a period of many years. Efficient, reusable and cheap adsorbing materials, however, are still missing. Here, we present a new, cheap and reusable chromate-adsorbing substrate based on polyvinylamine-coated polyester fibers. The surface modification of the fibrous material is realized by common methods in textile finishing yielding a durable, high-performing and reusable adsorbent for water-dissolved chromate. The functionalized nonwoven fabric has a high binding capacity for chromate and the chromate concentration of highly polluted waters (with concentrations around 50 mg L-1) can easily be decreased below the limit of 50 μg L-1 recommended by the WHO. Moreover, the material is reusable after regeneration under aqueous alkaline conditions. The adsorption properties at different pH values were determined with different adsorption models. In addition, adsorption kinetics were evaluated using artificial and real life chromate-contaminated water samples. This journal is © The Royal Society of Chemistry 2015.
    view abstract10.1039/c4ta04212c
  • Soft Nanocomposites-From Interface Control to Interphase Formation
    Pihan, S.A. and Emmerling, S.G.J. and Butt, H.-J. and Berger, R. and Gutmann, J.S.
    ACS Applied Materials and Interfaces 7 (2015)
    We report measurements of structure, mechanical properties, glass transition temperature, and contact angle of a novel nanocomposite material consisting of swellable silsesquioxane nanoparticles with grafted poly(ethyl methacrylate) (PEMA) brushes and PEMA matrices with varying molecular weight. We measured the interparticle distance at the surface of the composites using scanning probe microscopy (SPM) and in the bulk of ∼0.5 μm thick films by grazing incidence small angle X-ray scattering (GISAXS). For a given molecular weight of the brush unstable dispersions at high molecular weight of the matrix indicate an intrinsic incompatibility between polymer-grafted-nanoparticles and homopolymer matrices. This incompatibility is affirmed by a high contact angle between the polymer-grafted-nanoparticles and the high molecular weight matrix as measured by SPM. For unstable dispersions, we measured a decreased glass transition temperature along with a decreased plateau modulus by dynamic mechanical thermal analysis (DMTA) which indicates the formation of a liquid-like layer at the brush-matrix interface. This proves the ability to decouple the structural and mechanical properties from the potential to be swollen with small molecules. It opens a new area of use of these soft nanocomposites as slow release materials with tailored mechanical properties. © 2015 American Chemical Society.
    view abstract10.1021/am507572q
  • Strategies for permanent immobilization of enzymes on textile carriers
    Kiehl, K. and Straube, T. and Opwis, K. and Gutmann, J.S.
    Engineering in Life Sciences 15 (2015)
    The economical use of expensive enzymes in chemical synthesis can be improved by the immobilization of the catalyst on a suitable support material. Textile fabrics made of polyester, polyamide, or cotton represent comparatively inexpensive alternative carrier materials in contrast to conventional supports. Textile-inherent advantages like its flexible and lightweight construction allow the use in reactors of arbitrary geometry, a quick separation from the reaction liquor, and the generation of residue-free product. A low preparative and economical expense is needed to prepare fabrics with high enzyme loads (20-70 mg enzyme/g textile carrier), high relative activity (up to 20%) and excellent permanence against enzyme desorption as well. In this study, we present different strategies for the covalent fixation of enzymes on fiber forming polymers such as photochemical grafting, the use of bifunctional anchor molecules, monomeric, and polymeric cross-linking agents or specific enzyme modification for direct immobilization. In addition, we compare the strategies in terms of load, catalytic activity, and reusability. All presented immobilization methods yield products, which exhibit a considerable activity even after twenty recycling steps. In conclusion, we have successfully identified textiles as alternative, new and promising low cost carrier materials for enzymes. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
    view abstract10.1002/elsc.201400148
  • Temperature dependence of surface reorganization characteristics of amphiphilic block copolymer in air and in water studied by scanning force microscopy
    Lee, S. and Flores, S.M. and Berger, R. and Gutmann, J.S. and Brehmer, M. and Conrad, L. and Funk, L. and Theato, P. and Yoon, D.Y.
    Journal of Plastic Film and Sheeting 31 (2015)
    We have investigated the surface reorganization characteristics of a novel amphiphilic diblock copolymer, poly(acetic acid-2-(2-(4-vinyl-phenoxy)-ethoxy)-ethylester)-block-polystyrene (PAEES-b-PS), in response to varying interfaces from air to water and vice-versa at various temperatures. The surface reorganization characteristics of the block copolymer films was monitored by scanning force microscopy, in order to delineate the kinetically controlled morphological process of surface reorganization of a diblock copolymer, with a particular emphasis on the phase contrast signal which allowed the determination of local composition patterns of PAEES-b-PS at the surface. Upon heating a water-annealed sample in air, the initially hydrophilic liquid-like surface exhibited a typical dewetting pattern comprising holes and elevations of different copolymer components. In contrast, air-annealed samples with glassy polystyrene surfaces exhibited a distinctly different reorganization pattern upon heating in water, possibly due to the swelling of the underlying liquid-like hydrophilic block by penetrated water. In both air and water environments, the major surface reorganization occurred around 70, well below the glass transition temperature (100) of the higher T<inf>g</inf> block, polystyrene, in the copolymer. ©The Author(s) 2015.
    view abstract10.1177/8756087915595261
  • A novel approach for fixation of β-cyclodextrin on cotton fabrics
    Dehabadi, V.A. and Buschmann, H.-J. and Gutmann, J.S.
    Journal of Inclusion Phenomena and Macrocyclic Chemistry 79 (2014)
    Cyclodextrins are cyclic oligosaccharides, which form complexes with different organic substances such as drugs, odors, and etc. Due to the complexing abilities of cyclodextrins (CDs), they may also be used in textile industry as an auxiliary in washing, dyeing, and wastewater treatment. Fixation of CDs on textiles is possible using reactive derivatives of cyclodextrins or crosslinking agents. In this study we have investigated the use of polyaminocarboxylic acids (PACAs) as novel crosslinking agents for the fixation of β-CD on cotton fabrics. Fixation of β-CD on cotton fabric has been quantified by measuring the weight increase of the treated samples. The influence of the concentration of the catalyst (sodium hypophosphite) was studied, too. The presence of β-CD on the cotton has been investigated by the phenolphthalein test and host-guest complexation with organic volatile molecules: cyclohexene, chlorobenzene, cyclohexene-1-one and toluene. © 2013 Springer Science+Business Media Dordrecht.
    view abstract10.1007/s10847-013-0368-0
  • A study of photothermal laser ablation of various polymers on microsecond time scales
    Kappes, R.S. and Schönfeld, F. and Li, C. and Golriz, A.A. and Nagel, M. and Lippert, T. and Butt, H.-J. and Gutmann, J.S.
    SpringerPlus 3 (2014)
    To analyze the photothermal ablation of polymers, we designed a temperature measurement setup based on spectral pyrometry. The setup allows to acquire 2D temperature distributions with 1 μm size and 1 μs time resolution and therefore the determination of the center temperature of a laser heating process. Finite element simulations were used to verify and understand the heat conversion and heat flow in the process. With this setup, the photothermal ablation of polystyrene, poly(α-methylstyrene), a polyimide and a triazene polymer was investigated. The thermal stability, the glass transition temperature Tg and the viscosity above Tg were governing the ablation process. Thermal decomposition for the applied laser pulse of about 10 μs started at temperatures similar to the start of decomposition in thermogravimetry. Furthermore, for polystyrene and poly(α-methylstyrene), both with a Tg in the range between room and decomposition temperature, ablation already occurred at temperatures well below the decomposition temperature, only at 30–40 K above Tg. The mechanism was photomechanical, i.e. a stress due to the thermal expansion of the polymer was responsible for ablation. Low molecular weight polymers showed differences in photomechanical ablation, corresponding to their lower Tg and lower viscosity above the glass transition. However, the difference in ablated volume was only significant at higher temperatures in the temperature regime for thermal decomposition at quasi-equilibrium time scales. © 2014, Kappes et al.; licensee Springer.
    view abstract10.1186/2193-1801-3-489
  • Characterization of structural, mechanical and nano-mechanical properties of electrospun PGS/PCL fibers
    Salehi, S. and Bahners, T. and Gutmann, J.S. and Gao, S.-L. and Mäder, E. and Fuchsluger, T.A.
    RSC Advances 4 (2014)
    Physical and mechanical studies of aligned nanofibers of poly (glycerol sebacate) (PGS)/poly (ε-caprolactone) (PCL) designed for application in cornea tissue engineering are investigated. The fibers were fabricated by electrospinning different weight ratios of PGS and PCL (1:1, 2:1, 3:1, and 4:1), and had diameters in the range of 300-550 nm. DSC and XRD measurements showed that the overall crystallinity decreased with increasing amount of amorphous PGS in the composition. Accordingly, the elastic modulus of the fibers was found to decrease with increasing PGS/PCL blend ratio. In contrast, the surface modulus of the nanofibers, measured by nanoindentation, exceeded the elastic modulus by two orders of magnitude and increased with weight ratio of PGS. It is assumed that this is caused by the increasing content of PGS forcing the fiber-forming PCL into confined and cross-linked domains near the fiber surface. © 2014 the Partner Organisations.
    view abstract10.1039/c4ra01237b
  • Control of oil-wetting on technical textiles by means of photo-chemical surface modification and its relevance to the performance of compressed air filters
    Bahners, T. and Mölter-Siemens, W. and Haep, S. and Gutmann, J.S.
    Applied Surface Science 313 (2014)
    A two-step process comprising a surface roughening step by excimer laser irradiation and a post-treatment by photo-grafting to decrease the surface free energy was employed to increase the oil repellence of technical fabrics made of poly(ethylene terephthalate) (PET). The modification was designed to improve the performance of multi-layer filters for compressed air filtration, in which the fabrics served to remove, i.e. drain, oil separated from the air stream. In detail, the fibers surfaces were roughened by applying several laser pulses at a wavelength of 248 nm and subsequently photo-grafted with 1H,1H,2H,2H-perfluoro- decyl acrylate (PPFDA). The oil wetting behavior was increased by the treatments from full wetting on the as-received fabrics to highly repellent with oil contact angles of (131 ± 7)°. On surfaces in the latter state, oil droplets did not spread or penetrate even after one day. The grafting of PPFDA alone without any surface roughening yielded an oil contact angle of (97 ± 11)°. However, the droplet completely penetrated the fabric over a period of one day. The drainage performance was characterized by recording the pressure drop over a two-layer model filter as a function of time. The results proved the potential of the treatment, which reduced the flow resistance after 1-h operation by approximately 25%. © 2014 Elsevier B.V. All rights reserved.
    view abstract10.1016/j.apsusc.2014.05.146
  • Flame-retardant finishing of cotton fabrics using polyamino carboxylic acids and sodium hypophosphite
    Ameri Dehabadi, V. and Buschmann, H.-J. and Gutmann, J.S.
    Fire and Materials 38 (2014)
    The purpose of this research was to use polyamino carboxylic acids (PACAs) and their combination with sodium hypophosphite (NaH2PO2) as a flame-retardant finishing system for cotton fabrics. Flammability of cotton fabric was evaluated by 45° flammability test, differential scanning calorimetry and measuring the char yield. The combination of polyamino carboxylic acids and sodium hypophosphite as a phosphorus-containing catalyst reduces the flammability of cotton. The pyrolysis properties and the results of char yield of the finished cotton show that with increasing amount of catalyst, the flame retardancy increases. Fastness against multiple laundering, whiteness and tensile strength of the cotton finished with PACAs/NaH2PO2 to multiple standard laundering have been studied, too. The flame retardancy effect has an acceptable washing fastness. Whiteness and tensile strength of the finished cotton do not change significantly. Copyright © 2012 John Wiley & Sons, Ltd.
    view abstract10.1002/fam.2170
  • From spherical mesopores to worm-shaped mesopores: Morphology transition in titania-polystyrene-b-poly(ethylene oxide) composite films with increasing sol-gel reaction time
    Cheng, Y.-J. and Zhou, S. and Wolkenhauer, M. and Bumbu, G.-G. and Lenz, S. and Memesa, M. and Nett, S. and Emmerling, S. and Steffen, W. and Roth, S.V. and Gutmann, J.S.
    European Journal of Inorganic Chemistry 2014 (2014)
    A morphology transition from spherical mesopores to worm-shaped mesopores within titania block copolymer composite thin films has been observed by varying the sol-gel reaction time from 40 min to 48 h in the four-component templating system of polystyrene-b-poly(ethylene oxide) (PS-b-PEO), 1,4-dioxane, concentrated HCl, and titanium tetraisopropoxide (TTIP) with a PS-b-PEO mass concentration of 0.25 wt.-%. The impact of the sol-gel reaction time on the local structure, long-range lateral structure, and vertical structure of the as-prepared, calcined, and UV-degraded thin films as well as the structural changes in solution have been systematically investigated by scanning electron microscopy (SEM), atomic force microscopy (AFM), grazing-incidence small-angle X-ray scattering (GISAXS), X-ray reflectivity (XRR), and dynamic light scattering (DLS). With sol-gel reaction times of up to 5 h, hexagonally organized spherical micelles are present within the as-prepared composite films, in which the core of the spherical micelles is composed of the polystyrene (PS) block, and the corona is composed of the poly(ethylene oxide)-titania (PEO-titania) hybrid. Upon calcination or UV exposure, ordered mesoporous structures are formed owing to the removal of the PS block. With the sol-gel reaction time extended to 25 and 48 h, worm-shaped micelles appear, and their quantity increases with increasing sol-gel reaction time. Worm-shaped mesopores are formed by calcination or UV degradation. The GISAXS results prove that the local structural changes are representative over a macroscopic scale. The XRR results suggest that with the sol-gel reaction time extended to 48 h there is an additional thin layer beneath the mesoporous titania layer owing to the presence of a large amount of worm-shaped micelles. The results of the DLS studies imply that the morphology transition from spherical micelles to worm-shaped micelles is caused by a fusion process of the spherical micelles in solution. A morphology transition from spherical mesopores to worm-shaped mesopores within titania-polystyrene-b-poly(ethylene oxide) (titania-PS-b-PEO) composite thin films is achieved by varying the sol-gel reaction time from 40 min to 48 h with 0.25 wt.-% PS-b-PEO and fixed solution composition, as confirmed by imaging and scattering techniques. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
    view abstract10.1002/ejic.201301251
  • Generation of PGS/PCL blend nanofibrous scaffolds mimicking corneal stroma structure
    Salehi, S. and Fathi, M. and Javanmard, S.H. and Bahners, T. and Gutmann, J.S. and Ergün, S. and Steuhl, K.P. and Fuchsluger, T.A.
    Macromolecular Materials and Engineering 299 (2014)
    Morphological studies of aligned nanofibers scaffolds made of poly(glycerol sebacate)(PGS)/poly(-caprolactone)(PCL) blends for application as corneal tissue scaffolds are presented. Parallel conductive bars are used as ground electrode to generate unidirectional nanofibers. Scaffolds have fibers diameter in the range of 550-300nm. The structural stability and wettability, especially the in vitro degradation rate, of the electrospun scaffolds can be controlled by regulating the blended ratio of the polymers. The results indicate that PGS/PCL nanofiber scaffolds can be considered as ideal candidates for corneal tissue engineering scaffolds. The particular motivation for this work is to engineer a tissue-like construct that will mimic the stromal tissue of the cornea. Morphological and degradation studies of aligned nanofibers scaffolds made of poly(glycerol sebacate)(PGS)/poly(-caprolactone)(PCL) blends for corneal tissue engineering are reported. Scaffolds have fibers diameter in the range of 550-300nm. The motivation for this work is to engineer a tissue-like construct that will mimic the stromal tissue of cornea. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
    view abstract10.1002/mame.201300187
  • New nanofibrous scaffold for corneal tissue engineering
    Salehi, S. and Grünert, A.K. and Bahners, T. and Gutmann, J.S. and Steuhl, K.P. and Czugala, M. and Singer, B.B. and Fuchsluger, T.A.
    Klinische Monatsblatter fur Augenheilkunde 231 (2014)
    Background: An estimated 10 million people suffer worldwide from vision loss caused by corneal damage. For the worst cases, the only available treatment is transplantation with human donor corneal tissue. However, in numerous countries there is a considerable shortage of corneal tissue of good quality, leading to various efforts to develop tissue substitutes. The present study aims to introduce a nanofibrous scaffold of poly(glycerol sebacate) PGS as a biodegradable implant, for the corneal tissue engineering. Materials and Methods: Nanofibrous scaffolds were produced from PGS and poly(ε- caprolactone) (PCL) by a modified electro-spinning process. The biocompatibility of the material was tested in vitro by colorimetric MTT assay on days 3, 5, and 7 to test the cell viability of human corneal endothelium cells (HCEC). To examine a potential immunological reaction of the scaffolds, samples were exposed to mononuclear cells derived from peripheral blood (PBMCs). After an incubation period of 3 days, supernatants were assayed for apoptotic assessment and immunogenic potentials by annexin V FITC//propidium iodide and flow-cytometric analysis. Results: We could successfully demonstrate that cultivation of HCECs on PGS/PCL scaffolds was possible. Compared to day 3, cell density determined by microplate absorbance was significantly higher after 7 days of cultivation (p 0.0001). According to the MTT data, none of the samples showed toxicity. Apoptotic assessments by FACS analysis showed that no composition stimulated apoptosis or activated PBMCs occurred. All the compositions were inert for native as well as activated T/B/NK cells and monocytes. It can be concluded that leukocytes and their activity was not affected by the scaffolds. Conclusion: A tissue-like scaffold mimicking the human stroma could be developed. The results indicate that PGS/PCL scaffolds could be considered as ideal candidates for corneal tissue engineering as they are biocompatible in contact to corneal endothelial cells and blood cells. © 2014 Georg Thieme Verlag KG Stuttgart New York.
    view abstract10.1055/s-0034-1368533
  • Spectrophotometric estimation of the accessible inclusion sites of β-cyclodextrin fixed on cotton fabrics using phenolic dyestuffs
    Dehabadi, V.A. and Buschmann, H.-J. and Gutmann, J.S.
    Analytical Methods 6 (2014)
    Surface modified textiles with cyclodextrins are used in a wide range of applications. The presence of cyclodextrins on a textile material can be qualitatively proved by application of alkaline solutions of phenolphthalein and visual evaluation of the color change. However, there is no simple and universal method for quantitative determination of the amount of accessible cyclodextrins for complexation with guest molecules. In this article, we report a simple way based on colorimetric investigation of adsorption and desorption of phenolphthalein and phenol red in the cavities of cyclodextrins. To this end, woven cotton fabrics finished with different amounts of β-cyclodextrin were used. With the known stoichiometry of the complex formation of phenolic dyes with β-cyclodextrin, spectrophotometric study of complexation and decomplexation of these dyestuffs in cavities of cyclodextrins enables us to determine the accessible cyclodextrin sites quantitatively. © the Partner Organisations 2014.
    view abstract10.1039/c4ay00293h
  • Thin polyelectrolyte multilayers made by inkjet printing and their characterization by nanomechanical cantilever sensors
    Toda, M. and Chen, Y. and Nett, S.K. and Itakura, A.N. and Gutmann, J. and Berger, R.
    Journal of Physical Chemistry C 118 (2014)
    Measurements with nanomechanical cantilever (NMC) sensors often reveal only qualitative results. Here we overcome this issue by inkjet printing well-defined polyelectrolyte multilayers (PEMs). We present a method that allows fabricating a 40 bilayer (BL) thick and 5 mm long line made of poly(allylamine hydrochloride) (PAH) and polystyrene sulfonate (PSS). NMC sensors were used to quantify the uptake of water in thin PEMs. We measured and analyzed the mass loading and the swelling response of the PEMs upon exposure to relative humidity between 5% and 80%. For a film made of 5 BLs we determined a Young's module of ∼390 MPa for low humidity (<5%). Thicker PEM films made by 10 BLs exhibited a higher Young's module of ∼560 MPa. The Young's module decreased in both cases to 2-3 MPa at 80% relative humidity. Furthermore, the NMC measurements of mass and swelling upon exposure to humidity indicated a thickness-dependent swelling of the PEMs. © 2014 American Chemical Society.
    view abstract10.1021/jp501464j
  • Various strategies for the immobilization of biocatalysts on textile carrier materials
    Opwis, K. and Straube, T. and Kiehl, K. and Gutmann, J.S.
    Chemical Engineering Transactions 38 (2014)
    Textile fabrics made of polyester (PET), polyamide (PA) or cotton represent alternative carrier materials for the immobilization of enzymes. In contrast to conventional carriers, fiber materials are considerably inexpensive. The flexible construction of fabrics enables reactor constructions of any geometry and a quick removal of the catalyst without any residues after the reaction. Moreover, their open structure guarantees an optimal substrate turn-over and the active surface is easily adjustable by the fiber diameter. We have demonstrated successfully, that fabrics with a high enzyme load, a high relative activity and good permanence against enzyme desorption can be produced with low preparative and economic expense. Here, we report various methods for the permanent fixation of enzymes on fiber forming polymers such as photochemical grafting, the use of bifunctional anchor molecules, monomeric and polymeric cross-linking agents or specific enzyme modification for direct immobilization. In addition, we compare the strategies in terms of load, catalytic activity and reusability. © 2014, AIDIC Servizi S.r.l.
    view abstract10.3303/CET1438038
  • Wetting dynamics on superhydrophilic surfaces prepared by photonic microfolding
    Bahners, T. and Prager, L. and Gutmann, J.S.
    Langmuir 30 (2014)
    The wetting dynamic on microrough and perfectly wetting (superhydrophilic) acrylates was studied. These surfaces were achieved by coating polymer films made of poly(ethyleneterephthalate) (PET) with a hydrophilic acrylate based on hydroxypropylacrylate and polyethyleneglycolmonoacrylate, which was then cured and microroughened by photonic microfolding. The high transparency of the thin acrylate layers and polymer films allowed us to record the spreading of an applied water droplet through the film samples. Subsequently, the dynamic radius of the spreading pattern rc(t) was determined from the video recording. Various models for the wetting dynamics of superhydrophilic surfaces, namely, Tanner's law and a roughness-modified derivation published by McHale et al. in 2009, were then compared to the experimental results. Basically, the development of rc(t) in time was found to be in good agreement with McHale's model. Data analysis showed, however, that the initial phase of the spreading, that is, for t < 1 s, was not predicted well. This differing behavior relates well to a theory published by Cazabat and Cohen Stuart, who proposed that, on rough surfaces, spreading follows a power law in three time regimes. In this model, the (very) initial spreading is expected to be similar to the spreading on a smooth surface. © 2014 American Chemical Society.
    view abstract10.1021/la500227w
  • Correlation of material lifetime predictions by artificial aging vs. the relaxation master curve
    Bahners, T. and Schmidt, M. and Gutmann, J.S.
    Polymer Bulletin 70 (2013)
    With regard to lifetime prediction of technical textiles, the correlation of relaxation master curves (RMC) constructed from short-time relaxation measurements performed under variation of (a) elongation and (b) temperature with realtime behavior of PET fibers was studied. The comparison with relaxation measurements covering several days indicated that the actual behavior of the material was better described on the basis of the 'time-temperature-analogy'. Analyses of hydrolyzed material showed that the reliable construction of the RMC of aged monofils was possible by means of a 'time-aging parameter-analogy'. The obtained RMC exhibited a congruent shape to the RMC of the new material, but was shifted on the logarithmic time axis. It is concluded that this time-shift relates to the aging acceleration effected by the hydrolyzing procedure. The similarity of the shape of the curves also indicates, that the RMC of the new material gives a satisfactory prediction of the actual aging behavior. © Springer-Verlag Berlin Heidelberg 2013.
    view abstract10.1007/s00289-013-0951-y
  • Durable press finishing of cotton fabrics: An overview
    Dehabadi, V.A. and Buschmann, H.-J. and Gutmann, J.S.
    Textile Research Journal 83 (2013)
    Durable press (DP) or easy care finishing is almost always used for cotton fabrics or textiles with a high content of cellulosic fibers. This finish provides resistance against shrinkage and improved wet and dry wrinkle recovery to cellulosic textiles. Inhibition of easy movement of the cellulose chains by crosslinking with resins/polymers is the mechanism of a DP finish. Initially, derivatives of urea such as urea-formaldehyde and melamine-formaldehyde resins were used. Environmental concerns and the potential danger of formaldehyde led to the introduction of formaldehyde-free finishes. Among them, polycarboxylic acids such as 1,2,3,4-butanetetracarboxylic acids and citric acids are the most promising chemicals. To enhance the flexibility, tensile strength and whiteness of the easy care finished textiles, novel finishing agents have been recently considered; for example, ionic crosslinking, polyamino carboxylic acids and non-ionic polyurethane, as well as employing nano-materials as the catalyst or co-catalyst. The possible application of the easy care treatment with other functional finishes, mainly antimicrobial, flame retardancy and water–oil repellency, has been also been focused upon. © 2013, SAGE Publications. All rights reserved.
    view abstract10.1177/0040517513483857
  • Electric properties of organic thin-layers deposited by photo-polymerization on a textile substrate
    Bahners, T. and Wego, A. and Gutmann, J.S.
    Progress in Organic Coatings 76 (2013)
    The scope of the reported experiments was to study the charging behavior of photo-polymerized poly-DAP, poly-TAE and poly-PETA thin-layers, namely the remanence or storage of artificially deposited electric charges. The thin-layers were polymerized on the fibers of a technical non-woven under variation of the main parameters of the polymerization process, namely the monomer concentration in the applied precursor and the duration of UV exposure. The charging behavior of the layers was characterized by recording the charge dissipation after defined surface charging by a corona discharge. After the artificial charging, the electric field generated by residual surface charges was measured using an electric field mill as a function of time. It was found that the poly-DAP thin-layer showed no improvement in charge decay over the untreated sample. This is attributed to water absorption due to carboxylic groups. Poly-TAE and poly-PETA showed significant increases in charge remanence with increasing polymerization. It is proposed that the observed change in the electric property is related to increased cross-linking and reduced chain mobility with increasing UV exposure. Best results were achieved with poly-TAE holding, a thin-layer holding 1/e of the initial charge after more than 10 min. © 2012 Elsevier B.V. All rights reserved.
    view abstract10.1016/j.porgcoat.2013.07.001
  • Generalized synthesis of mesoporous rare earth oxide thin films through amphiphilic ionic block copolymer templating
    Xiao, Y. and You, S. and Yao, Y. and Zheng, T. and Lin, C. and Roth, S.V. and Müller-Buschbaum, P. and Steffen, W. and Sun, L.-D. and Yan, C.-H. and Gutmann, J.S. and Yin, M. and Fu, J. and Cheng, Y.-J.
    European Journal of Inorganic Chemistry (2013)
    A new concept to achieve the generalized synthesis of crystalline mesoporous rare earth (RE) oxide thin films templated with an ionic amphiphilic block copolymer is developed. Mesoporous La2O3, Eu 2O3, Tb2O3, and Yb2O 3 thin films as representatives of the light and heavy RE groups are synthesized by using polystyrene-block-poly(acrylic acid) (PS-b-PAA) as a templating agent. The impact of the concentration of PS-b-PAA on the morphologies of the mesopores is investigated. The local and long-range lateral structures, vertical structures, and crystallinities of the mesoporous thin films are probed by scanning electron microscopy, atomic force microscopy, grazing-incidence small-angle X-ray scattering, X-ray reflectivity, and transmission electron microscopy. The mechanism of formation of the mesoporous RE oxide thin films is discussed. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
    view abstract10.1002/ejic.201201524
  • Infiltration of polymer hole-conductor into mesoporous titania structures for solid-state dye-sensitized solar cells
    Rawolle, M. and Sarkar, K. and Niedermeier, M.A. and Schindler, M. and Lellig, P. and Gutmann, J.S. and Moulin, J.-F. and Haese-Seiller, M. and Wochnik, A.S. and Scheu, C. and Müller-Buschbaum, P.
    ACS Applied Materials and Interfaces 5 (2013)
    The degree of filling of titania nanostructures with a solid hole-conducting material is important for the performance of solid-state dye-sensitized solar cells (ssDSSCs). Different ways to infiltrate the hole-conducting polymer poly(3-hexylthiophene) (P3HT) into titania structures, both granular structures as they are already applied commercially and tailored sponge nanostructures, are investigated. The solar cell performance is compared to the morphology determined with scanning electron microscopy (SEM) and time-of-flight grazing incidence small-angle neutron scattering (TOF-GISANS). The granular titania structure, commonly used for ssDSSCs, shows a large distribution of particle and pore sizes, with porosities in the range from 41 to 67%, including even dense parts without pores. In contrast, the tailored sponge nanostructure has well-defined pore sizes of 25 nm with an all-over porosity of 54%. Filling of the titania structures with P3HT by solution casting results in a mesoscopic P3HT overlayer and consequently a bad solar cell performance, even though a filling ratio of 67% is observed. For the infiltration by repeated spin coating, only 57% pore filling is achieved, whereas filling by soaking in the solvent with subsequent spin coating yields filling as high as 84% in the case of the tailored titania sponge structures. The granular titania structure is filled less completely than the well-defined porous structures. The solar cell performance is increased with an increasing filling ratio for these two ways of infiltration. Therefore, filling by soaking in the solvent with subsequent spin coating is proposed. © 2012 American Chemical Society.
    view abstract10.1021/am302255c
  • Low-temperature sol-gel synthesis of nanostructured polymer/titania hybrid films based on custom-made poly(3-alkoxy thiophene)
    Niedermeier, M.A. and Rawolle, M. and Lellig, P. and Körstgens, V. and Herzig, E.M. and Buffet, A. and Roth, S.V. and Gutmann, J.S. and Fröschl, T. and Hüsing, N. and Müller-Buschbaum, P.
    ChemPhysChem 14 (2013)
    A low-temperature route to directly obtain polymer/titania hybrid films is presented. For this, a custom-made poly(3-alkoxy thiophene) was synthesized and used in a sol-gel process together with an ethylene-glycol-modified titanate (EGMT) as a suitable titania precursor. The poly(3-alkoxy thiophene) was designed to act as the structure-directing agent for titanium dioxide through selective incorporation of the titania precursor. The nanostructured titania network, embedded in the polymer matrix, is examined with atomic force microscopy (AFM) and scanning electron microscopy (SEM) measurements. By means of the scattering technique grazing incidence wide-angle X-ray scattering (GIWAXS), a high degree of crystallinity of the polymer as well as successful transformation of the precursor into the rutile phase of titania is verified. UV/Vis measurements reveal an absorption behavior around 500 nm which is similar to poly(3-hexyl thiophene), a commonly used polymer for photoelectronic applications, and in addition, the typical UV absorption behavior of rutile titania is observed. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
    view abstract10.1002/cphc.201200808
  • Morphology evolution in mesoporous titania block copolymer composite films with increasing Sol-Gel reaction time
    Cheng, Y.-J. and Zhou, S. and Wolkenhauer, M. and Bumbu, G.-G. and Lenz, S. and Memesa, M. and Nett, S. and Emmerling, S. and Steffen, W. and Gutmann, J.S.
    European Journal of Inorganic Chemistry (2013)
    A morphology evolution of thin films of titania from spherical mesopores to worm-shaped mesopores was realized by simply varying the sol-gel reaction time from 46 min to 25 h in the quadruple system consisting of polystyrene-block- poly(ethylene oxide) (PS-b-PEO), 1,4-dioxane, concentrated HCl, and titanium tetraisopropoxide (TTIP). Imaging techniques including scanning electron microscopy (SEM) and atomic force microscopy (AFM) were applied to investigate the local structure change of the as-prepared, calcined, and UV-degraded composite films. Grazing incidence small angle X-ray scattering (GISAXS) experiments prove that the structure change in local areas is representative of that over the macroscopic scale. An X-ray reflectivity (XRR) investigation reveals that the vertical structure change happens when the sol-gel reaction is extended from 5 to 25 h. A combination of imaging and scattering techniques provides a powerful tool to elucidate the impact of the sol-gel reaction time on the morphology evolution of the composite films. Dynamic light scattering (DLS) studies imply that the morphology evolution within the films is due to the structure change in solution. A mechanism of the morphology evolution with sol-gel reaction time is proposed on the basis of these results, which provide not only a new way to control the morphology of titania block copolymer composite films but also deep insights into the kinetics of the amphiphilic block copolymer templating process. Evolution of the morphology of TiO 2 thin films from spherical mesopores to worm-shaped mesopores has been achieved by simply varying the sol-gel reaction time of titanium tetraisopropoxide (TTIP) in the quadruple templating system copolymer PS-b-PEO, 1,4-dioxane, conc. HCl, and TTIP. Effective horizontal and vertical structure control is demonstrated at both the local and macroscopic scale. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
    view abstract10.1002/ejic.201201366
  • Nanoscale thermomechanics of wear-resilient polymeric bilayer systems
    Kaule, T. and Zhang, Y. and Emmerling, S. and Pihan, S. and Foerch, R. and Gutmann, J. and Butt, H.-J. and Berger, R. and Duerig, U. and Knoll, A.W.
    ACS Nano 7 (2013)
    We explore the effect of an ultrathin elastic coating to optimize the mechanical stability of an underlying polymer film for nanoscale applications. The coating consists of a several nanometer thin plasma-polymerized norbornene layer. Scanning probes are used to characterize the system in terms of shear-force-induced wear and thermally assisted indentation. The layer transforms a weakly performing polystyrene film into a highly wear-resistive system, ideal for high-density and low-power data storage applications. The result can be understood from the indentation characteristics with a hot and sharp indenter tip. The latter gives rise to a deformation mode in the fully plastic regime, enabling a simple interpretation of the results. The softening transition and the yield stress of the system on a microsecond time scale and a nanometer size scale were obtained. We show that the plastic deformation is governed by yielding in the polystyrene sublayer, which renders the overall system soft for plastic deformation. The ultrathin protection layer contributes as an elastic skin, which shields part of the temperature and pressure and enables the high wear resistance against lateral forces. Moreover, the method of probing polymers at microsecond and nanometer size scales opens up new opportunities for studying polymer physics in a largely unexplored regime. Thus, we find softening temperatures of more than 100 °C above the polystyrene glass transition, which implies that for the short interaction time scales the glassy state of the polymer is preserved up to this temperature. © 2012 American Chemical Society.
    view abstract10.1021/nn305047m
  • Organotextile catalysis
    Lee, J.-W. and Mayer-Gall, T. and Opwis, K. and Song, C.E. and Gutmann, J.S. and List, B.
    Science 341 (2013)
    Throughout human history, textiles have been integral to daily life, but their exploration in catalysis has been rare. Herein, we show a facile and permanent immobilization of organocatalysts on the textile nylon using ultraviolet light. The catalyst and the textile material require no chemical modification for the immobilization. All of the prepared textile-immobilized organocatalysts (a Lewis basic, a Brønsted acidic, and a chiral organocatalyst) display excellent stability, activity, and recyclability for various organic transformations. Very good enantioselectivity (>95:5 enantiomeric ratio) can be maintained for more than 250 cycles of asymmetric catalysis. Practical and straightforward applications of textile organocatalysis may be beneficial for various fields by offering inexpensive and accessible functionalized catalytic materials.
    view abstract10.1126/science.1242196
  • Pretreatment of cotton fabrics with polyamino carboxylic acids for salt-free dyeing of cotton with reactive dyes
    Ameri Dehabadi, V. and Buschmann, H..-J. and Gutmann, J.S.
    Coloration Technology 129 (2013)
    In this study, polyamino carboxylic acids have been used to improve the dyeability of cotton in a salt-free reactive dyeing process. These polyamino carboxylic acids were prepared by partial carboxylation of polyvinylamine. Cotton fabric was pretreated with polyamino carboxylic acids and dyed with reactive dyes. The colour strengths of the dyed fabrics were evaluated by measuring the K/S values. The fastness properties (washing, rubbing and light fastness) of the dyed cotton fabrics were also measured. The pretreatment of cotton with polyamino carboxylic acids creates positive charges on the fabric surface. In this way, salt-free reactive dyeing of cotton or dyeing with only a small amount of electrolyte is possible. © 2013 The Authors. Coloration Technology © 2013 Society of Dyers and Colourists.
    view abstract10.1111/cote.12010
  • Redox active polymer brushes with phenothiazine moieties
    Golriz, A.A. and Kaule, T. and Untch, M.B. and Kolman, K. and Berger, R. and Gutmann, J.S.
    ACS Applied Materials and Interfaces 5 (2013)
    We have investigated two different concepts to synthesize redox active polymer brushes using surface initiated atomic transfer radical polymerization (SI-ATRP). This polymerization technique allows the synthesis of well-defined grafted polymer brushes. In the initial step the surface was functionalized with a self-assembling monolayer of the SI-ATRP starter. Then, polymer brushes carrying phenothiazine moieties were grafted from the surface via SI-ATRP. The first concept consists of polymerizing monomers with phenothiazine pendant moieties to directly incorporate the redox functionality as side group in the growing polymer brush. The second concept consists of using grafted activated ester brushes which are functionalized with phenothiazine redox moieties in a successive reaction step. The electrochemical properties of the grafted redox active brushes were examined by cyclic voltammetry. Furthermore, the surface morphology and the chemical composition of the polymer brushes were characterized using scanning force microscopy (SFM), X-ray techniques, and UV/vis spectroscopy. Apart from their redox behavior, the synthesized brushes revealed increased mechanical stability on the nanoscale. © 2013 American Chemical Society.
    view abstract10.1021/am302869d
  • Simplifying cantilever sensors: Segmental analysis, a way to multiply your output
    Ochsmann, J.W. and Cavaliere, A. and Lenz, S. and Raitieri, R. and Gutmann, J.S. and Berger, R.
    Sensors and Actuators, B: Chemical 177 (2013)
    Bending experiments on micromechanical cantilevers (MMC) are a powerful tool to measure small amounts of chemical or biological analytes. By applying segmental cantilever readout technique we demonstrate that the investigation of MMC segments is sufficient to obtain reliable curvature values. This allows one to perform multiple bending experiments on a single MMC and by that to multiply the possible output per MMC. Furthermore we demonstrate how segmental MMC readout can be used to locate differently coated areas. © 2012 Elsevier B.V.
    view abstract10.1016/j.snb.2012.12.012
  • Study of easy care and biostatic properties of finished cotton fabric with polyamino carboxylic acids
    Ameri Dehabadi, V. and Buschmann, H.-J. and Gutmann, J.S.
    Journal of the Textile Institute 104 (2013)
    Polyamino carboxylic acids (PACAs) were used as novel finishing agents to create easy care and biostatic properties of cotton fabric. PACAs were synthesized by carboxylation of polyvinylamine with bromoacetic acid and 3-bromopropionic acid. The easy care effect was evaluated by measuring the wrinkle recovery angle and biostatic effect was estimated by the Formazan test. It was found that using PACAs create wrinkle resistant and biostatic cotton. Both properties were durable to multiple laundry wash. The impact of this finishing agent on the physical properties of the cotton was studied by evaluating the tensile strength and whiteness index of the finished cotton. The results showed that the use of PACAs as finishing agent did not make a considerable change on the physical properties of cotton. © 2013 Copyright The Textile Institute.
    view abstract10.1080/00405000.2012.738479
  • Super-wetting surfaces by plasma- and UV-based grafting of micro-rough acrylate coatings
    Bahners, T. and Prager, L. and Pender, A. and Gutmann, J.S.
    Progress in Organic Coatings 76 (2013)
    In Wenzel's model of the wetting behavior of rough surfaces, super-wetting can be achieved by micro-roughening a hydrophilic surface, but also by increasing the surface free energy of a micro-rough surface. Therefore, the objective of the present paper was to investigate the effect of grafting post-treatments of micro-rough surfaces having a good mechanical stability. The post-treatments were designed to increase the surface free energy and, accordingly, achieve pronounced surface wetting. Two potential designs of post-treatments were evaluated. A two-step plasma-based surface grafting and a UV-induced photo-chemical grafting. The plasma-based post-treatment was performed in a two-step process. First, the micro-rough samples were activated in argon or oxygen plasma. The subsequent grafting modification was carried out by immersing the samples in aqueous solutions of p-toluenesulfonic acid, glycerin, and saccharose. For the photo-chemical post-treatment, the micro-rough samples were dipped in an aqueous solution of poly(ethylene glycol) methacrylate (PEG300MA) and irradiated using a UV broadband lamp. Surface analysis showed that plasma-aided grafting resulted in the lowest water contact angles and extremely wetting surfaces. Following the photo-chemical grafting of PEG300MA, best results were of the order of 20. In both cases, excellent stability of the layer and its wetting behavior was found. © © 2013 Elsevier B.V. All rights reserved.
    view abstract10.1016/j.porgcoat.2013.04.007
  • A facile route to reassemble titania nanoparticles into ordered chain-like networks on substrate
    Cheng, Y.-J. and Wolkenhauer, M. and Bumbu, G.-G. and Gutmann, J.S.
    Macromolecular Rapid Communications 33 (2012)
    A facile route to reassemble titania nanoparticles within the titania-block copolymer composite films has been developed. The titania nanoparticles templated by the amphiphilic block copolymer of poly(styrene)-block-poly (ethylene oxide) (PS-b-PEO) were frozen in the continuous PS matrix. Upon UV exposure, the PS matrix was partially degraded, allowing the titania nanoparticles to rearrange into chain-like networks exhibiting a closer packing. The local structures of the Titania chain-like networks were investigated by both AFM and SEM; the lateral structures and vertical structures of the films were studied by GISAXS and X-ray reflectivity respectively. Both the image analysis and X-ray scattering characterization prove the reassembly of the titania nanoparticles after UV exposure. The mechanism of the nanoparticle assembly is discussed. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
    view abstract10.1002/marc.201100638
  • Characterization of the mechanical properties of technical fibers at extreme strain rates
    Bahners, T. and Schloßer, U. and Gutmann, J.
    Macromolecular Materials and Engineering 297 (2012)
    Technical textiles can be subject to mechanical stress with strain rates far from the quasi-static conditions of common standardized tests. The objective of the presented work was therefore to study the mechanical properties of technical yarns made of PA 6.6, PA 4.6, and PET under strain rates up to 200 s -1, making use of a "falling weight" apparatus. It can be summarized that the moduli at specific points of the stress-strain-curve increase with the strain rate to values up to 50% higher than the data determined under quasi-static strain. Saturation is observed for strain rates larger than 50 s -1. The analysis of failure morphology by scanning electron microscopy revealed molten material at the ends of broken fibers. This indicates thermal failure of the fibers due to local concentration of energy loading. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
    view abstract10.1002/mame.201100312
  • Comparative study of conventional and hybrid blocking layers for solid-state dye-sensitized solar cells
    Lellig, P. and Niedermeier, M.A. and Rawolle, M. and Meister, M. and Laquai, F. and Müller-Buschbaum, P. and Gutmann, J.S.
    Physical Chemistry Chemical Physics 14 (2012)
    In hybrid solar cells a blocking layer between the transparent electrode and the mesoporous titanium dioxide is used to prevent short-circuits between the hole-conductor and the front electrode. The conventional approach is to use a compact film of titanium dioxide. This layer has to be of optimum thickness: it has to cover the rough surface of the anode material completely while keeping it as thin as possible since the layer acts as an ohmic resistance itself. A competitive alternative arises when using an amphiphilic diblock copolymer as a functional template to produce thin, hybrid films containing a conducting titanium dioxide network embedded in an insulating ceramic material. These hybrid films can be produced much thinner compared to the conventional approach and, hence, they possess a 32% higher conductivity. The conventional and the hybrid blocking layer are characterized by conductive scanning probe microscopy and macroscopic conductance measurements. Additionally, the functionality of both blocking layers in solid-state dye-sensitized solar cells, as tested with current-voltage measurements, is verified. © the Owner Societies 2012.
    view abstract10.1039/c2cp23026g
  • Durable press finishing of cotton fabrics with polyamino carboxylic acids
    Dehabadi, V.A. and Buschmann, H.-J. and Gutmann, J.S.
    Carbohydrate Polymers 89 (2012)
    In this study, a polyamino carboxylic acid was synthesized by reaction of a commercial polyvinylamine and bromoacetic acid. The reaction product was used for crosslinking of cotton fabric by a pad-dry-cure process. Crosslinking of the finished cotton occurred via the formation of ester bonds between the carboxylic groups of the polyamino carboxylic acid and the hydroxyl groups of cellulose. Ester bonds were confirmed by appearance of the corresponding absorbance at 1730 cm -1 in the FTIR spectrum of the finished cotton. The created durable press effect on the finished cotton with polyamino carboxylic acid was evaluated by measuring the wrinkle recovery angle (WRA). Impact of this finishing agent on the physical properties of the cotton was studied by evaluating the tensile strength and whiteness index, and softness of the finished cotton. The easy care effect was durable against laundering. Softness, whiteness, and tensile strength of the finished cotton have not changed significantly. © 2012 Elsevier Ltd. All rights reserved.
    view abstract10.1016/j.carbpol.2012.03.047
  • Fabrication and characterization of nanostructured titania films with integrated function from inorganic-organic hybrid materials
    Rawolle, M. and Niedermeier, M.A. and Kaune, G. and Perlich, J. and Lellig, P. and Memesa, M. and Cheng, Y.-J. and Gutmann, J.S. and Müller-Buschbaum, P.
    Chemical Society Reviews 41 (2012)
    Nanostructured titania films are of growing interest due to their application in future photovoltaic technologies. Therefore, a lot of effort has been put into the controlled fabrication and tailoring of titania nanostructures. The controlled sol-gel synthesis of titania, in particular in combination with block copolymer templates, is very promising because of its high control on the nanostructure, easy application and cheap processing possibilities. This tutorial review gives a short overview of the structural control of titania films gained by using templated sol-gel chemistry and shows how this approach is extended by the addition of further functionality to the films. Different expansions of the sol-gel templating are possible by the fabrication of gradient samples, by the addition of a homopolymer, by the combination with micro-fluidics and also by the application of novel precursors for low-temperature processing. Moreover, hierarchically structured titania films can be fabricated via the subsequent application of several sol-gel steps or via the inclusion of colloidal templates in a one-step process. Integrated function in the block copolymer used in the sol-gel synthesis allows for the fabrication of an integrated blocking layer or an integrated hole-conductor. Both approaches grant a one-step fabrication of two components of a working solar cell, which make them very promising towards a cheap solar cell production route. Looking to the complete solar cell, the top contact is also of great importance as it influences the function of the whole solar cell. Thus, the mechanisms acting in the top contact formation are also reviewed. For all these aspects, characterization techniques that allow for a structural investigation of nanostructures inside the active layers are important. Therefore, the characterization techniques that are used in real space as well as in reciprocal space are explained shortly as well. © 2012 The Royal Society of Chemistry.
    view abstract10.1039/c2cs15321a
  • Frequency response of polymer films made from a precursor colloidal monolayer on a nanomechanical cantilever
    Liu, T. and Pihan, S. and Roth, M. and Retsch, M. and Jonas, U. and Gutmann, J.S. and Koynov, K. and Butt, H.-J. and Berger, R.
    Macromolecules 45 (2012)
    Nanomechanical cantilevers (NMC) were used for the characterization of the film formation process and the mechanical properties of colloidal monolayers made from polystyrene (PS). Closely packed hexagonal monolayers of colloids with diameters ranging from 400 to 800 nm were prepared at the air-water interface and then transferred in a controlled way on the surface of NMC. The film formation process upon annealing of the monolayer was investigated by measuring the resonance frequency of the NMC (≈12 kHz). Upon heating of non-cross-linked PS colloids, we could identify two transition temperatures. The first transition resulted from the merging of polymer colloids into a film. This transition temperature at 147 ± 3 °C as measured at ≈12 kHz remained constant for subsequent heating cycles. We attributed this transition temperature to the glass transition temperature T g of PS which was confirmed by dynamic mechanical thermal analysis (DMTA) and using the time temperature superposition principle. The second transition temperature (175 ± 3 °C) was associated with the end of the film formation process and was measured only for the first heating cycle. Furthermore, the transition of the colloidal monolayer into a homogeneous film preserved the mass loading on the NMC which allowed determination of the Young's modulus of PS (≈3 GPa) elegantly. © 2011 American Chemical Society.
    view abstract10.1021/ma202396h
  • Generation of biogas from textile waste waters
    Opwis, K. and Gutmann, J.S.
    Chemical Engineering Transactions 27 (2012)
    Conventional desizing of cotton is employed since several decades by the use of α-amylases, which hydrolize water-insoluble starch to water-soluble oligosaccharides. This enzymatic desizing process leads to waste waters with an extremely high chemical oxygen demand (COD) due to its high sugar content. Nowadays, these liquors are still disposed without use resulting in an ecological questionable pollution and high emission charges for cotton finishing manufacturers. Here, an innovative technology for the production of energy from textile waste waters from cotton desizing was developed. Such desizing liquors were fermented by methane-producing microbes to biogas. For this purpose a semi-industrial plant with a total volume of more than 500 L was developed and employed over a period of several weeks. The robust and trouble-free system produces high amounts of biogas accompanied with a significant reduction of the COD of more than 85 %. With regard to growing standards and costs for waste water treatment and disposal the new process can be an attractive alternative for textile finishing enterprises in waste water management combining economic and ecological benefits. Copyright © 2012, AIDIC Servizi S.r.l.
    view abstract10.3303/CET1227018
  • Gold-surface binding of molecular switches studied by Mössbauer spectroscopy
    Homenya, P. and Messerschmidt, M. and Tahir, M.N. and Martinez, V. and Cheng, Y. and Gutmann, J.S. and Klein, M. and Jung, S. and Wolff, M. and Saadat, R. and Nariaki, D. and Boča, R. and Klingelhöfer, G. and Tremel, W. and Renz, F.
    Hyperfine Interactions 205 (2012)
    The nonanuclear coordination compound [Mo IV{(CN)Fe III(3-methyl-saldptn)} 8]Cl 4 exhibits multiple spin transitions (3-methyl-saldptn = N,N′-bis(3′′-methyl-2′′-hydroxy-benzyliden)-1,7-diamino-4-azaheptane). This spin crossover cluster is bound via a self-assembled monolayer onto a two dimensional array gold surface. Mössbauer spectroscopy indicates that the thermally and optically induced spin crossover of the compound is maintained. Thereby, the foundation for its potential practical application (e. g. in the field of information storage) was laid. © 2011 Springer Science+Business Media B.V.
    view abstract10.1007/s10751-011-0426-1
  • Layer-by-layer fabrication of an anatase titania multilayer with gradual sponge-like morphology
    Perlich, J. and Memesa, M. and Diethert, A. and Metwalli, E. and Wang, W. and Roth, S.V. and Gutmann, J.S. and Müller-Buschbaum, P.
    Colloid and Polymer Science 290 (2012)
    The fabrication of a functional multilayer system with a gradually hierarchical order formed by individual titania thin films of different porosity is investigated. The porous or sponge-like nanostructures are fabricated using a diblock copolymer assisted sol-gel process. The successive spin-coating of the sol-gel solution onto the silicon substrate deposits a thin polymer nanocomposite film which is transformed to purely anatase titania nanostructures via calcination. In total, this procedure is repeated layer by layer for three times. This layer-by-layer approach is monitored with grazing incidence small-angle X-ray scattering (GISAXS) after each fabrication step. The GISAXS investigation is complemented in real space with a scanning electron microscopy characterization of the respective preparation stages. From the characterization, a porous titania multilayer system with gradually structured levels is clearly identified. © Springer-Verlag 2011.
    view abstract10.1007/s00396-011-2529-2
  • Oxidative in situ deposition of conductive PEDOT:PTSA on textile substrates and their application as textile heating element
    Opwis, K. and Knittel, D. and Gutmann, J.S.
    Synthetic Metals 162 (2012)
    Conductive organic polymers are outstanding materials with exciting properties. Besides several other applications - especially in the field of high-performance electric devices and photovoltaic technology - they can be used for the creation of conductive textile materials. Commercial dispersions of such polymers can be applied to textile constructions in a downstream coating process leading to poor add-ons and relatively low conductivity. In contrast, the authors have developed strategies to deposit conductive polymers by an oxidative in situ polymerization directly on the textile surface. Here, poly(3,4-ethylene dioxythiophene) p-toluenesulfonic acid (PEDOT:PTSA) was durably immobilized on a textile polyester fleece following this new approach. The extremely high achievable add-ons lead to extraordinary high-conductive textiles with surface resistances down to 10 Ω/sq. Such a way finished textiles can be used as high-performance textile heating elements. For example, by applying a standard voltage of 24 V temperatures up to 170 °C are practicable. Moreover, the desired temperature is easily adjustable by the absolute load and the applied voltage. These conductive textiles can be used, e.g., in carpets, electric blankets or automotive seat heaters. © 2012 Elsevier B.V.
    view abstract10.1016/j.synthmet.2012.08.007
  • Photo-initiated lamination of polyethylene (PE) and poly(ethylene terephthalate) (PET)
    Bahners, T. and Gutmann, J.S.
    Journal of Adhesion Science and Technology 26 (2012)
    Besides plasma-based processes, photo-initiated surface modifications have an interesting potential for adhesion promotion. This is of special interest with applications ranging from classical finishing to composites. Photo-chemical processes using continuous UV sources monochromatic as well as broad band are based on radical activation and ensuing reaction with the atmosphere. Achievable effects are addition of atoms e.g., introduction of oxygen (photo-oxidation) resulting in increased surface energy or grafting of functional groups. Both have certain potentials for adhesion promotion in a physico-chemical way. Based on the fundamental scheme of these processes i.e., a photon-initiated radical reaction at the substrate-atmosphere interface a direct 'inter-linking' of coating polymer and substrate is presented in this paper. The principal idea is to apply a thin layer of coating polymer on the substrate and irradiate this composite system at certain UV wavelengths. Given a low absorption of the radiation by the thin coating and at the same time a high absorption by the substrate, the radiation will penetrate the coating layer and generate radicals at the interface, which will induce cross-linking between the coating polymer and substrate. It is shown that for the example of laminates of polyethylene (PE) film on fabrics made of poly(ethylene terephthalate) (PET), extremely high adhesion strenghths are achieved without any use of additional adhesion promoters. © 2012 Copyright Taylor and Francis Group, LLC.
    view abstract10.1163/016942411X569336
  • Scanning Probe Methods: From Microscopy to Sensing
    Berger, R. and Gutmann, J. and Schäfer, R.
    Methods in Physical Chemistry 1 (2012)
    view abstract10.1002/9783527636839.ch24
  • Semi-industrial production of methane from textile wastewaters
    Opwis, K. and Mayer-Gall, T. and Gutmann, J.S. and Dammer, C. and Titscher, T. and Nickisch-Hartfiel, A. and Grün, O. and Spurk, C. and Schloderer, C. and Köppe, A. and Dörfler, C. and Bachus, H.
    Energy, Sustainability and Society 2 (2012)
    Background: The enzymatic desizing of starch-sized cotton fabrics leads to wastewaters with an extremely high chemical oxygen demand due to its high sugar content. Nowadays, these liquors are still disposed without use, resulting in a questionable ecological pollution and high emission charges for cotton finishing manufacturers. Methods: In this paper, an innovative technology for the production of energy from textile wastewaters from cotton desizing was developed. Such desizing liquors were fermented by methane-producing microbes to biogas. For this purpose, a semi-industrial plant with a total volume of more than 500 L was developed and employed over a period of several weeks. Results: The robust and trouble-free system produces high amounts of biogas accompanied by a significant reduction of the COD of more than 85%. With regard to growing standards and costs for wastewater treatment and disposal, the new process can be an attractive alternative for textile finishing enterprises in wastewater management, combining economic and ecological benefits. Conclusion: Moreover, the production of biogas from textile wastewaters can help to overcome the global energy gap within the next decades, especially with respect to the huge dimension of cotton pretreatment and, therefore, huge desizing activities worldwide. © 2012 Opwis et al; licensee Springer.
    view abstract10.1186/2192-0567-2-1
  • Stress-structure correlation in ps-pmma mixed polymer brushes
    Ochsmann, J.W. and Lenz, S. and Lellig, P. and Emmerling, S.G.J. and Golriz, A.A. and Reichert, P. and You, J. and Perlich, J. and Roth, S.V. and Berger, R. and Gutmann, J.S.
    Macromolecules 45 (2012)
    The ability to alter surface properties such as morphology and surface energy upon external stimuli makes switchable polymer surfaces a promising field of research. Mixed polymer brushes consisting of two different homopolymers covalently attached to a surface are one system in which surface properties can be switched. In this work the correlation between the change in structure and the resulting surface stress in thin poly(methyl methacrylate)-polystyrene mixed polymer brush film upon exposure to selective solvents is investigated. By measuring the forces acting inside the film, we are able to achieve a deeper understanding of the observed structural changes. To obtain a thorough understanding of the film's morphology, the structure is analyzed by scanning probe microscopy, X-ray reflectivity, and grazing incidence small-angle X-ray scattering (GISAXS). Upon exposure to acetic acid, a selective solvent for PMMA, the film showed a dimple-like structure. This is linked to collapsed domains of polystyrene covered by PMMA chains. Bending experiments resulted in tensile stress, pointing to attractive forces acting inside the polymer film. After exposure to dichloromethane, a good solvent for both polymers, bending experiments revealed a decreased but still high tensile stress, indicating that the microdomains are still present. The results of the experiments enable us to further explain the domain memory effect typically found in these kinds of mixed polymer brush systems. © 2012 American Chemical Society.
    view abstract10.1021/ma2025286
  • Super-hydrophilic surfaces by photo-induced micro-folding
    Bahners, T. and Prager, L. and Kriehn, S. and Gutmann, J.S.
    Applied Surface Science 259 (2012)
    A two-step UV curing process of thin acrylate layers was employed to prepare micro-rough top-coats on polymer film. The concept of the process (known as "photonic micro-folding") is to apply a thin acrylate layer on a substrate and cure the layer by subsequent exposures to VUV and broad band UV radiation. The first curing step leads to curing of the skin of the acrylate layer alone, which induces shrinkage and folding. This structure is fixed in the second curing step which affects the bulk of the acrylate layer. The process is easily applied to any substrate and large areas. By using hydrophilic hydroxypropylacrylate and polyethylenglycolmonoacrylate as the main components of the applied acrylate, perfectly wetting - super-hydrophilic - surfaces were obtained. This basically is in accordance with the concept of Wenzel's equation which relates the apparent contact angle to a roughness factor r given by the ratio of true and projected surface area. The analysis of the data of this work, however, shows that the spreading of a droplet on surfaces with r > 1.2 is governed by geometric effects such as blockage by the surface features and cannot by described by Wenzel's equation. © 2012 Elsevier B.V.
    view abstract10.1016/j.apsusc.2012.07.143
  • Surface modification of poly(ethylene terephthalate) fabric via photo-chemical reaction of dimethylaminopropyl methacrylamide
    Mohamed, N.H. and Bahners, T. and Wego, A. and Gutmann, J.S. and Ulbricht, M.
    Applied Surface Science 259 (2012)
    Photo-chemical reactions and surface modifications of poly(ethylene terephthalate) (PET) fabrics with the monomer dimethylaminopropyl methacrylamide (DMAPMA) and benzophenone (BP) as photo-initiator using a broad-band UV lamp source were investigated. The tertiary amino groups of the grafted poly(DMAPMA) chains were subsequently quaternized with alkyl bromides of different chain lengths to establish antibacterial activity. The surface composition, structure and morphology of modified PET fabrics were characterized by Fourier transform infrared spectroscopy (FTIR/ATR), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). To evaluate the amount of quaternary and tertiary ammonium groups on the modified surface, PET was dyed with an acid dye which binds to the ammonium groups. Therefore, the color depth is a direct indicator of the amount of ammonium groups. The resulting antibacterial activity of the modified PET fabrics was tested with Escherichia coli. The results of all experiments show that a photochemical modification of PET is possible using DMAPMA, benzophenone and UV light. Also, the quaternization of tertiary amino groups as well as the increase in antibacterial activity of the modified PET by the established quaternary ammonium groups were successful. © 2012 Elsevier B.V.
    view abstract10.1016/j.apsusc.2012.07.029
  • Temperature analysis of laser heated polymers on microsecond time scales
    Kappes, R.S. and Schönfeld, F. and Li, C. and Gutmann, J.S. and Butt, H.-J.
    Applied Physics A: Materials Science and Processing 106 (2012)
    To investigate the temperature profiles on laser heated polymer films, we track the thermal radiation with 1 μs time and 1 μm spatial resolution. The resulting two-dimensional temperature graphs are compared to finite element simulations in order to understand the heat conversion and flow. The temperature measurement setup consists of a NIR laser and an optical detection system, which includes high performance optics and a microsecond gated camera, equipped with several interference filters. In this way the thermal radiation is detected in the visible range with spectral resolution. Fitting the spectrum with Planck's law, two-dimensional micrographs of the temperature distribution are obtained. For polystyrene surfaces we were able to analyze the heating and the ablation behavior. Good agreement was found between experimental results and finite element simulations, when ablation is limited to a few tens of nanometers of the film thickness. Ablation of polystyrene starts at 150°C, 50 K above the glass transition temperature. We suggest a photomechanical ablation mechanism at that threshold fluence. For ablation at higher fluence and peak temperature, experiments indicate a thermal decomposition reaction. The temperature range of spinodal decomposition is not reached and can in our case be ruled out as ablation mechanism. © 2011 Springer-Verlag.
    view abstract10.1007/s00339-011-6715-3
  • Combination of acid-demineralization and enzymatic desizing of cotton fabrics by using industrial acid stable glucoamylases and α-amylases
    Dehabadi, V.A. and Opwis, K. and Gutmann, J.
    Starch/Staerke 63 (2011)
    In this study, the possibility of simultaneous acid-demineralization and enzymatic desizing of cotton fabric in acidic conditions (pH 2) by using industrial acid stable enzymes has been investigated. Acid-demineralization is necessary to remove undesired cationic metals and earth alkalis. Our experiments showed that by use of a mixture of two appropriate enzymes, a glucoamylase (Multifect GA 10L) and an α-amylase (Optisize Next) in a solution of citric acid and presence of a chelating agent, enzymatic desizing, and acid-demineralization can be successfully carried out at the same time. Therefore, two processes of pretreatment were integrated into a single process, which can effectively reduce time and costs for textile industry. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
    view abstract10.1002/star.201100028
  • Intercalation synthesis of functional hybrid materials based on layered simple hydroxide hosts and ionic liquid guests - A pathway towards multifunctional ionogels without a silica matrix?
    Delahaye, E. and Xie, Z. and Schaefer, A. and Douce, L. and Rogez, G. and Rabu, P. and Günter, C. and Gutmann, J.S. and Taubert, A.
    Dalton Transactions 40 (2011)
    Functional hybrid materials on the basis of inorganic hosts and ionic liquids (ILs) as guests hold promise for a virtually unlimited number of applications. In particular, the interaction and the combination of properties of a defined inorganic matrix and a specific IL could lead to synergistic effects in property selection and tuning. Such hybrid materials, generally termed ionogels, are thus an emerging topic in hybrid materials research. The current article addresses some of the recent developments and focuses on the question why silica is currently the dominating matrix used for (inorganic) ionogel fabrication. In comparison to silica, matrix materials such as layered simple hydroxides, layered double hydroxides, clay-type substances, magnetic or catalytically active solids, and many other compounds could be much more interesting because they themselves may carry useful functionalities, which could also be exploited for multifunctional hybrid materials synthesis. The current article combines experimental results with some arguments as to how new, advanced functional hybrid materials can be generated and which obstacles will need to be overcome to successfully achieve the synthesis of a desired target material. © The Royal Society of Chemistry 2011.
    view abstract10.1039/c1dt10841g
  • Investigating morphology and electronic properties of self-assembled hybrid systems for solar cells
    Lechmann, M.C. and Weber, S.A.L. and Geserick, J. and Hüsing, N. and Berger, R. and Gutmann, J.S.
    Journal of Materials Chemistry 21 (2011)
    We investigate self-assembled network morphologies of hybrid materials and their application in solar cells. We show the use of a semiconducting functional block copolymer as a structure directing agent. The application of a functional block copolymer circumvents an additional filling step of the templated inorganic part with a hole conductor. Within a one-pot synthesis various morphologies adequate for active materials in photovoltaic devices are prepared. The solar cell performance was found to depend on the morphological design of the hybrid material since the formation of percolating networks is of general importance. Using conductive scanning force microscopy on a cross-section of a functional solar cell device, we proved that the titania in our system forms a percolating network. Measurements showed that percolation is not a limiting factor for the device performance. In combination with a functionalized titania-precursor, we were able to double the power conversion efficiency of our hybrid bulk heterojunction cells in comparison to our previous results. © 2011 The Royal Society of Chemistry.
    view abstract10.1039/c1jm10928f
  • Melting and crystallization of poly(ethylene oxide) nanofilms studied by micromechanical cantilevers
    Zhao, J. and Yin, X. and Shi, J. and Zhao, X. and Gutmann, J.S.
    Journal of Physical Chemistry C 115 (2011)
    Melting and crystallization of thin poly(ethylene oxide) (PEO) films are studied by micromechanical cantilevers (MC) consisting of a micromachined silicon substrate with native oxide layer and a thin poly(ethylene oxide) coating. Phase transitions of the PEO nanofilms, such as melting and crystallization, appear as signals in the temperature-dependent deflection traces. The melting temperature (Tm) of thin films with thickness of 20-700 nm measured by MC is about 7-10 K lower than that of bulk samples measured by differential scanning calorimetry (DSC) due to the size effect and different crystallization conditions. However, the crystallization temperature (Tc) obtained by MC and DSC is almost the same. Both Tm and Tc measured by MC increase with increasing film thickness. Besides, both Tm and Tc decrease with increasing number of heating-cooling cycles due to partial dewetting of the polymer films from the silicon oxide substrate surface, which results in a decreased contact area and adhesion strength at the interface. © 2011 American Chemical Society.
    view abstract10.1021/jp205381b
  • Morphology and photoluminescence study of titania nanoparticles
    Memesa, M. and Lenz, S. and Emmerling, S.G.J. and Nett, S. and Perlich, J. and Müller-Buschbaum, P. and Gutmann, J.S.
    Colloid and Polymer Science 289 (2011)
    Titania nanoparticles are prepared by sol-gel chemistry with a poly(ethylene oxide) methyl ether methacrylate-block-poly(dimethylsiloxane)- block-poly(ethylene oxide) methyl ether methacrylate triblock copolymer acting as the templating agent. The sol-gel components-hydrochloric acid, titanium tetraisopropoxide, and triblock copolymer-are varied to investigate their effect on the resulting titania morphology. An increased titania precursor or polymer content yields smaller primary titania structures. Microbeam grazing incidence small-angle X-ray scattering measurements, which are analyzed with a unified fit model, reveal information about the titania structure sizes. These small structures could not be observed via the used microscopy techniques. The interplay among the sol-gel components via our triblock copolymer results in different sized titania nanoparticles with higher packing densities. Smaller sized titania particles, (∼13-20 nm in diameter) in the range of exciton diffusion length, are formed by 2% by weight polymer and show good crystallinity with less surface defects and high oxygen vacancies. © 2011 The Author(s).
    view abstract10.1007/s00396-011-2421-0
  • Nanostructuring of titania thin films by a combination of microfluidics and block-copolymer-based sol-gel templating
    Rawolle, M. and Ruderer, M.A. and Prams, S.M. and Zhong, Q. and Magerl, D. and Perlich, J. and Roth, S.V. and Lellig, P. and Gutmann, J.S. and Müller-Buschbaum, P.
    Small 7 (2011)
    Sol-gel templating of titania thin films with the amphiphilic diblock copolymer poly(dimethyl siloxane)-block-methyl methacrylate poly(ethylene oxide) is combined with microfluidic technology to control the structure formation. Due to the laminar flow conditions in the microfluidic cell, a better control of the local composition of the reactive fluid is achieved. The resulting titania films exhibit mesopores and macropores, as determined with scanning electron microscopy, X-ray reflectivity, and grazing incidence small angle X-ray scattering. The titania morphology has three features that are beneficial for application in photovoltaics: 1) a large surface-to-volume ratio important for charge generation with disordered hexagonally arranged mesopores of 25 nm size and a film porosity of up to 0.79, 2) enhanced light scattering that enables the absorption of more light, and 3) a dense titania layer with a thickness of about 6 nm at the substrate (bottom electrode) to prevent short circuits. An optical characterization complements the structural investigation. Microfluidics and sol-gel templating are combined to design titania thin films with well defined structures. The obtained films consist of mesopores with a diameter of 25 nm and macropores, as seen with scanning electron microscopy and grazing incidence small angle X-ray scattering. This structure is interesting for potential applications in inorganic-organic photovoltaics because of the large surface area and enhanced light scattering as compared to structures templated without microfluidics. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
    view abstract10.1002/smll.201001734
  • Nanowear in a nanocomposite reinforced polymer
    Pihan, S.A. and Emmerling, S.G.J. and Butt, H.-J. and Gutmann, J.S. and Berger, R.
    Wear 271 (2011)
    We investigated the reinforcement of blends made from poly(ethyl methacrylate) (PEMA) and PEMA-grafted nanoparticles at a nanometer length scale. The reinforcement was probed by nanowear experiments based on scanning force microscopy (SFM). In addition to imaging, the SFM is applied to wear the surface of samples at the length scale of nanoparticles. Blends with different miscibility of nanoparticles were prepared by varying the molecular weights of polymer grafted from the nanoparticles (N) and polymer forming the matrix (P). We were able to associate a critical force for the onset of nanowear by analyzing the nanowear patterns resulting from different normal loads during the nanowear experiment. The definition of this critical force allows quantitative comparison of nanoparticle-polymer systems of different composition. Nanowear tests indicated that only mixtures where N/P> 1 reinforced the composite material compared to the pure homopolymer. Under these conditions the grafted polymers were swollen and the nanoparticles acted as additional anchor sites. As reference experiments we used a blend made from PEMA homopolymer and unmodified particles. Non-grafted nanoparticles clearly did not account for any reinforcement. © 2011 Elsevier B.V.
    view abstract10.1016/j.wear.2011.05.040
  • Organic proton-conducting molecules as solid-state separator materials for fuel cell applications
    Jiménez-García, L. and Kaltbeitzel, A. and Enkelmann, V. and Gutmann, J.S. and Klapper, M. and Müllen, K.
    Advanced Functional Materials 21 (2011)
    Organic proton-conducting molecules are presented as alternative materials to state-of-the-art polymers used as electrolytes in proton-exchanging membrane (PEM) fuel cells. Instead of influencing proton conductivity via the mobility offered by polymeric materials, the goal is to create organic molecules that control the proton-transport mechanism through supramolecular order. Therefore, a series of phosphonic acid-containing molecules possessing a carbon-rich hydrophobic core and a hydrophilic periphery was synthesized and characterized. Proton conductivity measurements as well as water uptake and crystallinity studies (powder and single-crystal X-ray analysis) were performed under various conditions. These experiments reveal that proton mobility is closely connected to crystallinity and strongly dependent on the supramolecular ordering of the compound. This study provides insights into the proton-conducting properties of this novel class of materials and the mechanisms responsible for proton transport. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
    view abstract10.1002/adfm.201002357
  • Redox active polymers with phenothiazine moieties for nanoscale patterning via conductive scanning force microscopy
    Golriz, A.A. and Kaule, T. and Heller, J. and Untch, M.B. and Schattling, P. and Theato, P. and Toda, M. and Yoshida, S. and Ono, T. and Butt, H.-J. and Gutmann, J.S. and Berger, R.
    Nanoscale 3 (2011)
    Redox active polymers with phenothiazine moieties have been synthesized by Atomic Transfer Radical Polymerization (ATRP). These novel polymers reveal bistable behaviour upon application of a bias potential above the oxidation threshold value. Using conductive Scanning Force Microscopy, two distinguishable conductivity levels were induced on a nanoscale level. These levels were related to a high conducting "On" and a low conducting "Off" state. The "On" state is generated by the oxidation of the phenothiazine side chains to form stable phenothiazine radical cations. The formation and stability of the radical sites was examined by cyclic voltammetry, electron spin resonance and optical spectroscopy. Polymers with phenothiazine moieties show the ability to retain their redox state for several hours and can therefore be used for nonvolatile organic memory devices. Furthermore, thin films made from the phenothiazine containing polymers show high mechanical nanowear stability. © 2011 The Royal Society of Chemistry.
    view abstract10.1039/c1nr10917k
  • Softening of PMMA brushes upon collapse/swelling transition. A combined neutron reflectivity and nanomechanical cantilever sensor study
    Lenz, S. and Rühm, A. and Major, J. and Berger, R. and Gutmann, J.S.
    Macromolecules 44 (2011)
    In this work, we establish a direct correlation between chain mechanics and structural properties of polymer brushes upon swelling. We present experimental results on poly(methyl methacrylate) (PMMA) brushes prepared via surface initiated atomic transfer radical polymerization. Neutron reflectivity studies gave insight into the brush thickness and volume fraction profiles of the brush, gradually swollen with solvent mixtures. Comparison of our experiments with scaling theory yielded specific polymer - solvent interaction parameters and gave insight into the desorption and adsorption behavior of bad and good solvents, respectively. Insight into the brush's chain mechanics was obtained from surface stress investigations using the nanomechanical cantilever sensor bending technique. It was shown that polymer brush swelling leads to a decrease in surface stress due to chain disentanglements and the related softening of the polymer brush under θ-solvent conditions. © 2010 American Chemical Society.
    view abstract10.1021/ma1021715
  • Surface modification of textile materials with hydrophobins
    Opwis, K. and Gutmann, J.S.
    Textile Research Journal 81 (2011)
    Hydrophobins are native proteins with outstanding properties. Because of their special bifunctional molecular structure they can influence the wetting behavior of polymeric substrates. Here, the influence of thermally deposited hydrophobins on properties of various textile substrates is studied. The successful immobilization of hydrophobins can be demonstrated by a protein-selective color reaction with ninhydrin, which is positive even after a harsh washing and extraction procedure indicating the high permanence of the finishing process. Regarding the wetting properties, the modification of hydrophobic fabrics (demonstrated on polyethylene terephthalate) results in a significant hydrophilization, while hydrophilic textile substrates made of cotton and polyamide attain strong hydrophobic character. Moreover, the developed thermal deposition technique seems to be practical for use with coating technologies established in the textile industry and could be easily transferred to industrial praxis. Thus, non-toxic and biodegradable hydrophobins copied from nature could have great potential in textile surface modification. © 2011, SAGE Publications. All rights reserved.
    view abstract10.1177/0040517511404599
  • Comparison of hybrid blends for solar cell application
    Lechmann, M.C. and Koll, D. and Kessler, D. and Theato, P. and Tremel, W. and Gutmann, J.S.
    Energies 3 (2010)
    In blended hybrid systems distinct micro- or nanostructured materials can be formed by phase separation. Network structures of particles or rods in a polymer matrix can be developed via self-assembly. We use this blending approach to compare active materials for application in solar cell devices. Blends were fabricated from either poly(hexylthiophene) P3HT or poly(triphenylamine) PTPA mixed with nanocrystalline TiO 2 rods. In this manner, we compare two different hole conducting polymers in their performance in photovoltaic devices, while experimental conditions are kept identical. We find that the choice of solvent and photovoltaic characterization conducted in inert atmosphere is of importance for blends prepared from P3HT/TiO 2 blends, but not for PTPA/TiO 2 blends. Even though prepared with the same TiO 2 rods, solar cells prepared from PTPA blends showed an enhanced efficiency when measured under ambient conditions. Furthermore, the PTPA/TiO 2 showed higher long-term stability. © 2010 by the authors; licensee Molecular Diversity Preservation International, Basel, Switzerland.
    view abstract10.3390/en3030301
  • Electrical scanning probe microscopy of an integrated blocking layer
    Weber, S.A.L. and Memesa, M. and Berger, R. and Butt, H.-J. and Gutmann, J.S.
    Journal of Nanoscience and Nanotechnology 10 (2010)
    Scanning probe microscopy was performed on an integrated blocking layer system developed for hybrid organic solar cells. A nanocomposite consisting of titania and an amphiphilic triblock copolymer ((PEO)MA-PDMS-MA(PEO)) was prepared by sol-gel chemistry. After plasma treatment and annealing of a spin casted film of 30-100 nm thickness a granular structure with a typical titania grain diameter of 20 nm was found. Conductive scanning force microscopy revealed that on top of almost every grain on the surface there is an increased conductivity compared to the average value. The correlation of grains and conductivity indicated that titania particles formed interconnecting paths through the film. For the resistivity of these pathways we found that effects of tip-sample and sample-electrode resistivity dominate. Additionally, conductive scanning force microscopy revealed non-conducting structures attributed to the thermal treatment. Kelvin probe microscopy of pristine samples on one side and plasma treated plus annealed samples on the other side showed that there is a shift in work function (0.8±0.2 eV) as expected for the transition of amorphous to anatase titania. Copyright © 2010 American Scientific Publishers.
    view abstract10.1166/jnn.2010.2974
  • Global scattering functions: A tool for grazing incidence small angle X-ray scattering (GISAXS) data analysis of low correlated lateral structures
    Lenz, S. and Bonini, M. and Nett, S.K. and Lechmann, M.C. and Emmerling, S.G.J. and Kappes, R.S. and Memesa, M. and Timmann, A. and Roth, S.V. and Gutmann, J.S.
    EPJ Applied Physics 51 (2010)
    In this article we discuss the applicability of global scattering functions for structure analysis of Grazing Incidence Small Angle X-ray Scattering (GISAXS) data. Contrary to rigorous analysis of the full 2-D detector image, which can be performed with complex simulation models, the global scattering functions described here will be used to model transverse detector scans in the q11 reciprocal scattering planes. In contrast to a full GISAXS analysis, this procedure cannot explain structural features perpendicular to the sample plane. The discussed method is useful for the analysis of weakly correlated films. These films are e.g. found in polymer inorganic composite materials based on commercially available nanoparticles. In hybrid material systems polydisperse structures, including particle aggregates without precisely defined shape are formed. The pictured approach, which models scattering in terms of structural levels, has been previously applied with success in conventional transmission SAXS geometry. It is based on conventional exponential and power laws. Hence, data analysis becomes less complex compared to simulation approaches. Here we examine if this unified fitting model can be used to model diffuse, non specular scattering resulting from GISAXS. In this context the applicability and limit of its application to diffuse scattering in the GISAXS geometry is discussed. Furthermore diffuse q11 scattering from different ideal particle types is simulated and compared with fitted results. To verify our approach, fit results from experimental GISAXS curves obtained for real samples are compared with results from Scanning Probe Microscopy and Scanning Electron Microscopy studies. The samples investigated range from evaporated Au films to hybrid TiO2/polymer films and demonstrate the usefulness in the structural analysis of complex films. © EDP Sciences 2010.
    view abstract10.1051/epjap/2010064
  • Patterning of a surface immobilized ATRP initiator with an inkjet printer
    Emmerling, S.G.J. and Langer, L.B.N. and Pihan, S.A. and Lellig, P. and Gutmann, J.S.
    Macromolecules 43 (2010)
    A new technique for patterning polymer brushes on the micrometer scale has been developed in which an inkjet printer was used to deposit droplets of acid on a surface-immobilized initiator for atom transfer radical polymerization (ATRP). The acid cleaved an ester bond in the ATRP initiator in a saponification reaction. As a result, the ATRP initiator was rendered inactive. To control the degree of defunctionalization, a new initiator containing a weak ester bond was derived from a tertiary alcohol. Comparison to an established ATRP initiator, derived from a primary alcohol, showed that the novel initiator was defunctionalized with a higher efficiency. Control of the reaction time allowed to partially defunctionalize the initiator molecules, leading to control of grafting densities within the written patterns. © 2010 American Chemical Society.
    view abstract10.1021/ma902836n
  • PS-b-PEO block copolymer thin films as structured reservoirs for nanoscale precipitation reactions
    Ochsmann, J.W. and Lenz, S. and Emmerling, S.G.J. and Kappes, R.S. and Nett, S.K. and Lechmann, M.C. and Roth, S.V. and Gutmann, J.S.
    Journal of Polymer Science, Part B: Polymer Physics 48 (2010)
    Thin films of PS-b-PEO block copolymers were utilized as structured reservoirs for localized nanoscale precipitation reactions. By consecutively immersing the film into solutions of thioacetamide and cadmium chloride, we were able to obtain a monolayer of cadmium sulfide nanostructures on top of the block copolymer film. AFM and grazing incidence small angle X-ray scattering revealedspherical nanostructures (d = 15 nm) corresponding to the dimensions given by the block copolymer film. © 2010 Wiley Periodicals, Inc.
    view abstract10.1002/polb.21967
  • Template-free structuring of colloidal hetero-monolayers by inkjet printing and particle floating
    Retsch, M. and Dostert, K.-H. and Nett, S.K. and Vogel, N. and Gutmann, J.S. and Jonas, U.
    Soft Matter 6 (2010)
    Here we demonstrate the feasibility of a novel approach to simultaneously pattern surfaces with heterogeneous colloidal monolayers on various length scales from tens of m down to nanometres by a combination of simple inkjet printing and nanosphere lithography. The process involves inkjet printing of different particle types in a pre-pattern with sparsely distributed particles on an initial substrate. After immersion in water the particles float off the substrate and self-assemble into a dense and hexagonally ordered colloidal monolayer, with a concomitant 1D contraction of the pre-pattern along the immersion direction. While nanosphere lithography yields the nanostructures, the superimposed m scale pattern is defined by the inkjet printing process, leading to hexagonally ordered colloidal monolayers of various particles sizes or materials in parallel. Since the m pattern with arbitrary shape is simply designed on a computer and printed, the process does not require any customized template or mask to be fabricated. Due to its simplicity the computer-assisted method shows great potential for automatization, which should substantially improve structure quality and turn it into a technologically promising approach. © 2010 The Royal Society of Chemistry.
    view abstract10.1039/c001306d
  • Thermal response of surface grafted two-dimensional polystyrene (PS)/polyvinylmethylether (PVME) blend films
    Lenz, S. and Nett, S.K. and Memesa, M. and Roskamp, R.F. and Timmann, A. and Roth, S.V. and Berger, R. and Gutmann, J.S.
    Macromolecules 43 (2010)
    This work shows that phase separations in 2D polymer films can be tuned by employing entropically constraining grafting points. We present experimental results on surface-grafted 2D polystyrene (PS)/polyvinylmethylether (PVME) blended films using surface-anchored benzophenone derivates. In contrast with 2D films that have not been grafted, it was possible to raise the blended lower critical solution temperature (LCST) above room temperature by using low grafting point densities. Highly constrained films did not show polymer-polymer phase separation. In addition to the in situ structural analysis performed with surface probe microscopy (SPM), μ-beam-sized grazing incidence small-angle X-ray scattering (μ-GISAXS), and μ-X-ray reflectivity (μ-XRR), surface stress investigations performed using nanomechanical cantilever sensor (NCS) arrays gave detailed insight into the phase separation mechanism. Phase separations were shown to result in dominating attractive entropie spring mechanisms with opposing repulsive effects resulting from surface and interfacial energy changes. © 2009 American Chemical Society.
    view abstract10.1021/ma9021696
  • Time-resolved, local temperature measurements during pulsed laser heating
    Kappes, R.S. and Li, C. and Butt, H.-J. and Gutmann, J.S.
    New Journal of Physics 12 (2010)
    To analyse processes during laser heating, one needs to be able to measure temperatures of about 1000 K within one microsecond and with micrometre resolution. To achieve this accuracy, we set up a high-performance optical detection system with a microsecond gated camera in combination with selected interference filters to detect the thermal emission spectrum in the visible range. By fitting the emission spectrum to Planck's law, we are able to collect an area temperature profile for time intervals as short as one microsecond. Thus we can show that a polymer film, which is doped with an organic dye for energy conversion, can reach temperatures of at least 900 K, which is high above its 'normal' decomposition temperature. It is, furthermore, possible to relate the temperature to the effect of the laser beam on the polymer film. © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.
    view abstract10.1088/1367-2630/12/8/083011
  • atomic force microscopy

  • block copolymers

  • coatings

  • polymer films

  • polymers

  • scanning electron microscopy

  • sensors

  • thin films

  • tissue engineering

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