Publications - Microscopy on Polymer Systems by Yi and Ralf Thomann

Freiburg University	Publications - Dr. Yi Thomann 2005-2009
52: Gradient Interfaces in SBS and SBS/PS Blends and Their Influence on Morphology Development and Material Properties. Yi Thomann, Ralf Thomann, Alfred Hasenhindl, Rolf Mülhaupt, Barbara Heck, Konrad Knoll, Helmut Steininger, Kay Saalwächter Macromolecules 2009, 42(15), 5684-5699. Abstract: The formation of gradient interfaces between PS- and PB-rich microphases in SBS block copolymers was investigated by means of solid-state NMR and solution NMR as well as TEM, AFM, and SAXS as a function of molecular architecture, comparing linear and star-shaped asymmetric block structures, and gradient as well as random incorporation of styrene comonomer into the PB-rich blocks. Although all studied SBS possess a very similar total styrene content, different morphologies and mechanical properties were found in the extruded SBS/PS blends, whose origin could be related to the formation of a compositional interface gradient. Employing the sensitivity of solid-state NMR for hard (glassy) and soft (rubbery) phases as well as their respective chemical compositions, we found that upon raising the temperature up to the PS glass transition different amounts of polystyrene from the hard PS phase "soften" and integrate into the soft PB-rich phase ("PS softening"). The degree of "PS softening" characterizes the interfacial gradients of SBS block copolymers at elevated temperatures up to the melt. The softened PS was found to partially mix into the soft phase and partially remain at the interface, thus forming different gradient interfaces, depending primarily on the amount of styrene randomly incorporated in the PB mobile blocks and much less on a compositional gradient at the block linkages in SBS chains. In SBS/PS blends, SBS with a substantial "PS softening" effect was found to preferentially form elongated PB lamellar morphologies, which lead to improved mechanical ductility. The purpose of this study was to apply different characterization methods and correlate their results in order to gain important compositional and morphological information as well as their effects on the SBS/PS blend mechanical properties. Rapid and robust low-cost pulsed solid-state NMR methods were established as versatile analytical tools for application in high-output polymer screening (HOPS) and quality control systems, enabling online monitoring of structure-property correlations as well as product quality of SBS-based materials. 51: Column high-temperature gradient adsorption liquid chromatography - a novel way of separation for polyolefins T. Macko,R. Brüll, Y. Wang, Y. Thomann The Column (electronic journal), September 4 (2009) 15 50: Separation of propene/1-alkene and ethylene/1-alkene copolymers by high-temperature adsorption liquid chromatography. Tibor Macko, Robert Bruell, Rufina G. Alamo, Yi Thomann, V. Grumel Polymer (2009), 50(23), 5443-5448. Abstract: A high performance liq. chromatog. column (HPLC) Hypercarb packed with porous graphite has proven to discriminate polyolefin mols. due to differences in their adsorption and desorption behavior. While linear polyethylene (PE) and syndiotactic polypropylene (sPP) are adsorbed on the graphite packing, isotactic polypropylene (iPP) is not adsorbed. The column operates at 160 C with 1-decanol as sample solvent and mobile phase. We have now tested this HPLC system for sepns. of random propene/1-alkene and ethylene/1-hexene copolymers: While copolymers of propene with 1-butene, 1-hexene and 1-octene copolymers eluted in size exclusion mode without adsorption, propene/1-octadecene and ethylene/1-hexene copolymers are strongly retained and eluted only after application of a linear gradient starting from 1-decanol and ending with pure 1,2,4-trichlorobenzene. The retention of propene/1-alkene (>11 carbons in the side chain) copolymers increases with the concn. of comonomer, making this HPLC system suitable to sep. these copolymers according to their chem. compn. In contrast, the retention of ethylene/1-hexene samples decreases with increasing 1-hexene content. Branching in this case shortens the length of continuous methylene sequences of the polymer backbone, which are expected to adsorb in a planar conformation to the graphite layers. This is the first report on the sepn. of short chain branched polyolefins by high-temp. adsorption liq. chromatog. 49: Separation of ethylene/1-alkene and propylene/1-alkene copolymers by high-temperature adsorption liquid chromatography. Tibor Macko, Robert Brull, Rufina Alamo, Yi Thomann Abstracts of Papers, 238th ACS National Meeting, Washington, DC, United States, August 16-20, 2009 Abstract: Linear low d. polyethylenes (LLDPE) are applied for prodn. of various folies, which are used as packaging materials including short-chain branching into polyethylene or polypropylene enables to modify the phys. properties of resulting copolymers in a wide range. Amt. and distribution of the alkyl groups in the polymer chains play a crucial role. Sepn. based on monitoring of crystallinity of LLDPE, such as TREF and CRYSTAF, are used for study of the branching distribution. We present, as an alternative, chromatog. sepn. of the ethylene/1-alkene and propylene/1-alkene copolymers. Polymer samples are dissolved in a single solvent and injected into a HPLC column at temp. 160 C. Depending on the length of the branches, the copolymers are either eluted or strongly adsorbed. Retained samples are desorbed after application of a solvent gradient. The elution order of both the ethylene/1-alkene and propylene/1-alkene copolymers depend on their chem. compn. 48: Amphiphilic Conetworks Based on End-Linked Multiblock Copolymers of Different Numbers of Blocks and Constant Molecular Weight and Composition Natalie A. Hadjiantoniou, Costas S. Patrickios, Yi Thomann, Joerg C. Tiller Macromol. Chem. Phys. 2009, 210, 942-950 Abstract: Amphiphilic conetworks based on end-linked copolymers of the hydrophilic ionizable 2-(dimethylamino)ethyl methacrylate and the hydrophobic n-butyl methacrylate bearing 3, 5, 7, and 9 blocks were synthesized using group transfer polymerization, and employing a bifunctional initiator and sequential addition of monomers and ethylene glycol dimethacrylate cross-linker. All the linear precursors to the conetworks had the same molecular weight and composition, and differed only in their number of blocks. The aqueous degrees of swelling of the ionized conetworks increased with the number of blocks, manifesting the reduction of the driving force for nanophase separation, resulting from the reduction of the length of the hydrophobic segments. Reduction in the tendency for nanophase separation with increasing block number was also supported by atomic force microscopy on bulk conetworks, which indicated a decrease in the domain size as the number of blocks increased. 47: Tailoring of poly(vinyl alcohol) cryogels properties by salts addition. S. Patachia, C. Florea, C. Friedrich, Y. Thomann eXPRESS Polymer Letters (2009), 3(5), 320-331 Abstract: Pyrolytic carbon black (PCB) made from used tires was used in ethylene-propylene-diene copolymers (EPDM). The microstructure of PCB was characterized by scanning electron microscopy (SEM). PCB was compounded with EPDM to prepare EPDM vulcanizates. The effects of PCB on the processing properties of EPDM compounds and the mechanical properties of vulcanizates were investigated and compared with other traditional fillers such as semi-reinforcing furnace black (N774), light calcium carbonate (CaCO3) and thermal black (N990). At the same time, the rheological behavior of EPDM compounds filled with different fillers was characterized by capillary rheometrics. The SEM photos showed that the particle shape was quiet different from that of CaCO3 and N990, it was similar to that of N774. The primary particle size was smaller than that of N774, but the aggregate size of PCB was larger than that of N774. The effect of PCB on the processing properties of EPDM compounds was similar to that of other fillers. Among the four fillers, PCB imparted EPDM compounds with higher Mooney viscosity. With the increase of filler content, the scorch time and optimum curing time of EPDM compounds changed little. The reinforcing effect of PCB was similar to that of N990, but inferior to that of N774. With the increase of PCB content, tensile strength, tear strength, and modulus at 100% elongation of EPDM vulcanizates increased significantly. When EPDM was filled with 50 phr PCB, the tear strength of EPDM vulcanizates increased by 3 times, compared with that of EPDM gum vulcanizates. The appearance of EPDM extrudate filled with PCB was coarser than that of other fillers. 46: Correlation between poly(vinyl alcohol) cryogel swelling capacity and synthesis parameters S.F.C. Patachia, D. Rinja, C. Friedrich, Y. Thomann Chapter 14 in "Recent Advances in Research on Biodegradable Polymers and Sustainable Composites: Vol. 3" Alfonso Jimenez (Herausgeber), Gennady E. Zaikov (Herausgeber) Nova Science Publishers Inc. (Oktober 2008) 45: A simple nanostructured polymer/ZnO hybrid solar cell - preparation and operation in air Frederik C. Krebs, Yi Thomann, Ralf Thomann, Jens W. Andreasen NANOTECHNOLOGY, Volume: 19, Issue: 42, Article Number: 424013, Published: OCT 22 2008 Abstract: A detailed description is given of the preparation of a polymer solar cell and its characterization. The solar cell can be prepared entirely in the ambient atmosphere by solution processing without the use of vacuum coating steps, and it can be operated in the ambient atmosphere with good operational stability under illumination (1000 W m(-2), AM1.5G, 72 +/- 2 degrees C, 35 +/- 5% relative humidity) for 100 h with a 20% loss in efficiency with respect to the initial performance. The dark storability (darkness, 25 degrees C, 35 +/- 5% relative humidity) has been shown to exceed six months without notable loss in efficiency. The devices do not require any form of encapsulation to gain stability, while a barrier for mechanical protection may be useful. The devices are based on soluble zinc oxide nanoparticles mixed with the thermocleavable conjugated polymer poly-(3-(2-methylhexan-2-yl)-oxy-carbonyldithiophene) (P3MHOCT), which through a thermal treatment is converted to the insoluble form poly(3-carboxydithiophene) (P3CT) that generally gives stable polymer solar cells. The devices employed a solution based silver back electrode. One advantage is that preparation of the devices is very simple and can be carried out by hand under ambient conditions, requiring only a hot plate that can reach a temperature of 210 degrees C, and preferably also a spincoater. This type of device is thus excellently suited for teaching and demonstration purposes provided that the materials are at hand. 44: Boehmite nanorod-reinforced-polyethylenes and ethylene/1-octene thermoplastic elastomer nanocomposites prepared by in situ olefin polymerization and melt compounding. TS. Halbach, Y.Thomann, R. Mülhaupt JOURNAL OF POLYMER SCIENCE PART A-POLYMER CHEMISTRY, 46, 8, 2755-2765, 2008 Abstract: Nanocomposites of polyethylene (HDPE) and poly(ethylene-co-1-octene) thermoplastic elastomers, both containing boehmites with variable sizes, shapes, and aspect ratios (1-20), were prepared by means of in situ olefin polymerization and melt compounding. The in situ olefin polymerization in the presence of boehmite nanorods afforded nanocomposites containing 4-8 wt % of boehmite. In an alternative process, the in situ olefin polymerization was used to produce polyolefins with high boehmite content of 50 wt % as masterbatches for polyolefin melt compounding with ethylene homo- and copolymers. The addition of the boehmite nanofillers improved the stiffness without sacrificing high elongation at break. The stiffness, as expressed by Young's modulus, increased with increasing boehmite aspect ratio. In case of thermoplastic elastomer nanocomposites the increase of stiffness was accompanied by a simultaneous increase of elongation at break. According to transmission electron microscopy (TEM), fine dispersion of the polar boehmite nanorods and nanoplatelets within the nonpolar hydrocarbon polymer matrix was obtained without requiring the addition of special dispersing agents or functionalized polyolefin compatibilizers. The comparison of melt compounding of polyethylene with boehmites or polyethylene/boehmite masterbatches revealed that compounding of masterbatches prepared by in situ polymerization filling afforded much finer and more uniform nanoboehmite dispersions. 43: Direct Observation of Interphase Composition in Block Copolymers. Saalwächter, Kay; Thomann, Yi; Hasenhindl, Alfred; Schneider, Horst. Macromolecules (2008), 41(23), 9187-9191. Abstract: We demonstrate the fast, direct, and quant. observation of temp.- and comonomer-induced changes in the interfacial size and compn. in phase-sepd. styrene-butadiene-styrene block copolymers by double-quantum-filtered proton spin-diffusion NMR expts. performed under high-resoln. magic-angle spinning conditions. The expt. is based on the dipolar-mediated diffusion of spin magnetization from the (styrenic) rigid phase through a more mobile interphase of variable size and compn. into the soft (polybutadiene) domain. The expt. spectroscopically distinguishes between mobilized styrene segments located in the interphase and those mixed (dissolved) in the bulk of the mobile domain. The results indicate that temp.-induced softening due to mobilization of styrene units at the interface and the tendency to become part of an extended interphase is stronger for systems with a lower segregation strength, having statistically distributed styrene comonomers in the soft domain. 42: Structural characterization of glassy and rubbery model anionic amphiphilic polymer conetworks. Kali, Gergely; Georgiou, Theoni K.; Ivan, Bela; Patrickios, Costas S.; Loizou, Elena; Thomann, Yi; Tiller, Jörg C. ACS Symposium Series (2008), 996, 286-302. Abstract: The structure of two series of model amphiphilic polymer conetworks based on the hydrophilic anionic methacrylic acid was characterized by at. force microscopy (AFM) and small-angle neutron scattering (SANS). In the first series, the hydrophobic component was the glassy poly(Me methacrylate), while the rubbery poly(2-butyl-1-octyl methacrylate) constituted the hydrophobic segments in the second series. Each series comprised conetworks in which the hydrophile / hydrophobe ratio was systematically varied as well as conetworks with different architecture of the linear chain: ABA and BAB triblock and statistical. The AFM and SANS measurements indicated nanophase sepn. in the triblock copolymer-based conetworks and provided the spacing, size and shape of the formed nanodomains. 41: Spin-diffusion NMR at low field for the study of multiphase solids. Mauri, M.; Thomann, Y.; Schneider, H.; Saalwaechter, K. Solid State Nuclear Magnetic Resonance (2008), 34(1-2), 125-141. Abstract: The use of spin-diffusion NMR for the measurement of domain sizes in multiphase materials is becoming increasingly popular, in particular for the study of heterogeneous polymers. Under conditions where T 1 relaxation can be neglected, which is mostly the case at high field, anal. and approx. solns. to the evolution of spin diffusion are available. In order to extend the technique to more general conditions, we performed a comprehensive study of the diffusion of magnetization in a model copolymer at low field, where T 1 tends to be of the same order of magnitude as the typical spin-diffusion time. In order to study the effects of T 1 and to delineate the optimal T 1 values for back correction prior to applying the initial-rate approxn., we developed a numerical simulation based on the diffusion equation and including longitudinal relaxation. We present and discuss the limits of simple correction strategies for initial-slope anal. based on apparent relaxation times from satn.-recovery expts. or the spin-diffusion expts. themselves. Our best strategy faithfully reproduces domain sizes obtained by both TEM investigations and full simultaneous fitting of spin-diffusion and satn.-recovery curves. Full fitting of such independent data sets not only yields correct domain sizes, but also the true longitudinal relaxation times, as well as spin-diffusion coeffs. Effects of interphases with distinct mobility on spin-diffusion curves, as well as practical hints concerning the reliable component decompn. of the detected low-resoln. FID signal by help of different magnetization filters are also discussed in detail. 40: Acrylic nanocomposite resins for use in stereolithography and structural light modulation based rapid prototyping and rapid manufacturing technologies. Gurr, Matthias; Hofmann, Daniel; Ehm, Michael; Thomann, Yi; Kübler, Rainer; Mülhaupt, Rolf. Advanced Functional Materials (2008), 18(16), 2390-2397. Abstract: A novel family of optically transparent acrylic nanocomposites contg. up to 30 wt % silica nanoparticles with an av. diam. of 20 nm was developed for application in structural light modulation (SLM) and stereolithog. (SL) technologies. The uniform dispersion of nanoparticles affords a significantly improved toughness/stiffness-balance of the photopolymd. and postcured nanocomposites. It is possible to increase stiffness, as expressed by Young's modulus, from 1290 to 1700 MPa without encountering the embrittlement typical for many other conventional filled polymers. Fracture behavior is examd. by means of fracture mechanics investigation and SEM analyses of fracture surfaces. According to TEM analyses and measurement of optical transmittance remarkable uniform dispersion of silica nanoparticles was achieved. The silica nanoparticle concns. up to 17 wt % give only marginally higher viscosities and do not affect transmittance, while slightly increasing the exposure times needed in photopolymn. Moreover, the silica nanoparticles afford materials with reduced shrinkage and improved properties. The green effective ankle splay out (EASO) measured on H-shaped diagnostic specimens, is significantly reduced for the nanocomposite materials from 1.38 mm for the unfilled material to 0.82 mm for nanocomposites contg. 30 wt % nanosilica. The building accuracy is increased significantly with increasing content of silica nanofillers. 39: Nanophase Separated Anionic Amphiphilic Model Polymer Conetworks Based on Methacrylic acid G. Kali, T.K. Georgiou, B. Ivan, C.S. Patrickios, E. Loizou, Y. Thomann and J. Tiller NSTI Nanotech 2007, Nanotechnology Conference and Trade Show, Santa Clara, CA, United States, May 20-24, 2007, 2, 60-63. Abstract: Two series of model amphiphilic polymer conetworks were synthesized by group transfer polymerization (GTP). The first one was composed of the hydrophobic methyl methacrylate (MMA) and the hydrophilic methacrylic acid (MAA), and the second one contained 2-butyl-1-octyl methacrylate (BOMA) as the hydrophobic monomer and MAA. Anionic amphiphilic model conetworks and the BOMA monomer were synthesized and investigated for the first time. The network synthesis was performed by sequential monomer/cross-linker additions to form conetwork series in a wide range of composition and architecture. All conetwork precursors and the extractables were characterized by gel permeation chromatography and nuclear magnetic resonance spectroscopy to determine the molecular weights and compositions, respectively. The polymer conetworks were investigated in terms of their degree of swelling in aqueous media and in THF. The thermal and mechanical properties were determined by differential scanning calorimetry and dynamic mechanical analyses, respectively. These results indicate the differences between the MMA and BOMA conetwork series. The nanophase separated structure was proved by atomic force microscopy (AFM) and small angle neutron spectroscopy (SANS) for the triblock copolymer model conetworks but not for the networks with random monomer distributions. 38: Synthesis and Characterization of Anionic Amphiphilic Model Conetworks of 2-Butyl-1-Octyl-Methacrylate and Methacrylic Acid: Effects of Polymer Composition and Architecture. Kali, Gergely; Georgiou, Theoni K.; Ivan, Bela; Patrickios, Costas S.; Loizou, Elena; Thomann, Yi; Tiller, Jörg C. Langmuir (2007), 23(21), 10746-10755. Abstract: Seven amphiphilic conetworks of methacrylic acid (MAA) and a new hydrophobic monomer, 2-butyl-1-octyl-methacrylate (BOMA), were synthesized using group transfer polymn. The MAA units were introduced via the polymn. of tetrahydropyranyl methacrylate (THPMA) followed by the removal of the protecting tetrahydropyranyl group by acid hydrolysis after network formation. Both THPMA and BOMA were inhouse synthesized. Ethylene glycol dimethacrylate (EGDMA) was used as the cross-linker. Six of the conetworks were model conetworks, contg. copolymer chains between cross-links of precise mol. wt. and compn. The prepd. conetwork series covered a wide range of compns. and architectures. In particular, the MAA content was varied from 67 to 94 mol %, and three different conetwork architectures were constructed: ABA triblock copolymer-based, statistical copolymer-based, and randomly cross-linked. The linear conetwork precursors were analyzed by gel permeation chromatog. and 1H NMR spectroscopy in terms of their mol. wt. and compn., both of which were found to be close to the theor. calcd. values. The degrees of swelling (DS) of all the amphiphilic conetworks were measured in water and in THF over the whole range of ionization of the MAA units. The DSs in water increased with the degree of ionization (DI) and the content of the hydrophilic MAA units in the conetwork, while the DSs in THF increased with the d.p. of the chains between the cross-links and by reducing the DI of the MAA units. Finally, the nanophase behavior of the conetworks was probed using small-angle neutron scattering and at. force microscopy. 37: Structural characterization of glassy and rubbery anionic amphiphilic model conetworks. Kali, Gergely; Georgiou, Theoni K.; Ivan, Bela; Patrickios, Costas S.; Loizou, Elena; Thomann, Yi; Tiller, Jörg Abstracts of Papers, 233rd ACS National Meeting, Chicago, IL, United States, March 25-29, 2007 Abstract: The structure of two series of amphiphilic model conetworks based on the hydrophilic anionic methacrylic acid was characterized by at. force microscopy (AFM) and small-angle neutron scattering (SANS). In the first series the hydrophobic component was the glassy poly(Me methacrylate), while the rubbery poly(2-butyl-1-octyl methacrylate) constituted the hydrophobic segments in the second series. Each series comprised conetworks in which the hydrophile / hydrophobe ratio was systematically varied as well as conetworks with different architecture of the linear chain: ABA and BAB triblock and statistical. The measurements indicated nanophase sepn. in the triblock copolymer-based conetworks and provided the spacing, size and shape of the formed nanodomains. 36: Synthesis and Characterization of Anionic Amphiphilic Model Conetworks Based on Methacrylic Acid and Methyl Methacrylate: Effects of Composition and Architecture. Kali, Gergely; Georgiou, Theoni K.; Ivan, Bela; Patrickios, Costas S.; Loizou, Elena; Thomann, Yi; Tiller, Joerg C. Macromolecules, (2007), 40(6), 2192-2200. Abstract: A series of amphiphilic conetworks of methacrylic acid (MAA) and Me methacrylate (MMA) were synthesized using group transfer polymn. (GTP). The MAA units were introduced via the polymn. of tetrahydropyranyl methacrylate (THPMA), followed by the removal of the protecting tetrahydropyranyl group by acid hydrolysis after network formation. 1,4-Bis(methoxytrimethylsiloxymethylene)cyclohexane (MTSCH) was used as a bifunctional GTP initiator, while ethylene glycol dimethacrylate (EGDMA) served as the cross-linker. Nine of the conetworks were model conetworks, comprising copolymer chains between the cross-links of precise mol. wt. and compn. Eight of the model conetworks were based on ABA triblock copolymers, while the ninth was based on a statistical copolymer. The tenth conetwork was not model but randomly cross-linked. The mol. wt. and the compn. of the linear conetwork precursors were analyzed by gel permeation chromatog. and 1H NMR, resp., and were found to bear values close to the theor. expected. FTIR spectroscopic analyses indicated complete polymn. of the EGDMA crosslinker vinyl units and complete hydrolysis of the THPMA units. The degrees of swelling (DS) of all the conetworks were measured in water and in THF as a function of the degree of ionization (DI) of the MAA units. The DSs in water increased with the DI of the MAA units (and the pH), while the DSs in THF presented the opposite trend. Finally, small-angle neutron scattering and at. force microscopy confirmed nanophase sepn. in a triblock copolymer-based model conetwork and lack of it in its statistical copolymer counterpart. 35: Iridescent Colors from Films Made of Polymeric Core-Shell Particles He, Xu; Thomann, Yi; Leyrer, Reinhold J.; Rieger, Jens. Polymer Bulletin, (2006), 57(5), 785-796. Abstract: Brilliant and angle-dependent iridescent color films were obtained from polymer films produced via colloidal crystn. of monodisperse core-shell particles by drying aq. dispersions. The core is a styrene copolymer and the shell is a Me methacrylate copolymer. Through variation of the particle size, the brilliant color could be varied throughout the visible spectrum. The color effects of the smooth thin films exhibit excellent thermal and water stability. The morphol. of the core-shell particles and the properties of the corresponding films were characterized by dynamic light scattering (DLS), at. force microscopy (AFM), differential scanning calorimetry (DSC), and reflection spectrum measurements. The brightness of the film is strongly dependent on size and quality of the cryst. domains. 34: Living random and block copolymerization of ethene and propene on a tailor-made phenoxyimine catalyst and characterization of the resulting high molecular weight PE-block-P(E-co-P) block copolymers. Weiser, Marc-Stephan; Thomann, Yi; Heinz, Lars-Christian; Pasch, Harald; Mülhaupt, Rolf. Polymer (2006), 47(13), 4505-4512. Abstract: The phenoxyimine catalyst (bis(N-(3',5'-diiodo-salicylidene)-2,6-difluoroaniline)-titanium(IV)-dichloride) was tailored to enable random and block copolymn. of propylene and ethylene with compns. covering the entire feasible compn. range. Well-defined high mol. wt. diblock copolymers of the type PE-block-P(E-co-P), consisting of a semi-cryst. polyethylene and a soft P(E-co-P) block, were prepd. and evaluated with respect to propylene content and the block lengths. The characterization by means of AFM, CRYSTAF data and high temp. chromatog. elution provided the exptl. evidence that no homo-polyethylene and less than 5% of the random copolymer are formed as byproducts. 33: PMMA Gradient Materials and in situ Nanocoating via Self-Assembly of Semifluorinated Hyperbranched Amphiphiles Yi Thomann, R. Haag, R. Brenn, R. Delto, H. Weickman, R. Thomann, R. Mülhaupt. Macromol. Chem. Phys. 2005, 206, 134-141 Abstract: Nanostructured poly(methyl methacrylate) (PMMA) gradient materials with in situ nanocoating were obtained via self-assembly of semifluorinated hyperbranched polyglycerol amphiphiles (FPG) at the PMMA surface during free-radical MMA bulk polymerisation. The FPG was designed as novel nanoadditive and prepared by etherification of the hydrophilic hyperbranched polyglycerol core with allylether and subsequent quantitative addition of the hydro- and oleophobic 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluoro-octane-1-thiol to the double bond end groups. As a result of the FPG self-assembly, a fluorine-containing nanocoating, with an average thickness of 150 to 200 nm at the PMMA surface, was detected by transmission electron microscopy (TEM) and Rutherford backscattering spectrometry (RBS) of an 4He+ beam. The resulting nanocoating formation was driven by the interactions of the perfluorohexyl end groups and the in situ phase separation with increasing conversion of the MMA polymerisation. The FPG nanocoating consisted of a nanolayered substructure composed of alternating fluorine-containing and fluorine-free layers with an average thickness of 3-5 nm, which was evidenced by atomic force microscopy (AFM) and small angle X-ray scattering (SAXS). Very small amounts of the FPG amphiphile, typically less than 3 wt.-% added to PMMA, were found to be sufficient to achieve the in situ nanocoating formation at the PMMA surface. The surfaces of the PMMA/FPG surface gradient materials were water and oil repellent. 32: Nanophase Separated Amphiphilic Microbeads. Savin, Gabriela; Bruns, Nico; Thomann, Yi; Tiller, Jörg C. Macromolecules (2005), 38(18), 7536-7539. Abstract: Nanostructured nonporous amphiphilic polymeric microbeads and their evaluation as catalyst support. A hydrophobic polymeric crosslinker, a,w-methacrylate-terminated poly(dimethylsiloxane), MA-PDMS-MA, was copolymd. with trimethylsilylated 2-hydroxyethyl acrylate (TMSOEA) using photoinitiator Irgacure 651 in a surfactant soln. and phosphate buffer, irradiated at 340 nm for 3 min to yield a hydrophobic precursor network. Upon subsequent cleavage of the TMS groups, an amphiphilic, nanophase sepd. network formed. The type of surfactant used as emulsifier in polymn. has an important effect on compn. and morphol. of the microbeads. A dispersion of spherical polymer particles showing phase sepd. bulk morphol. was obtained. The amphiphilic polymer microbeads show a continuous nanostructure from the inside to the surface, the PHEA segments form a sponge-like continuous phase with domain size of about 3-6 nm and the PDMS domains (18-30 nm) are embedded into the PHEA structure. The amphiphilic PHEA-l-PDMS microbeads were evaluated as phase transfer matrix for catalysis, in a-chymotrypsin (CT) catalyzed transesterification of N-acetyl-L-phenylalanine Et ester (APEE) with propanol in n-octane to N-acetyl-L-phenylalanine Pr ester (APPE). 31: Epoxy-layered silicate nanocomposites as matrix in glass fibre-reinforced composites X. Kornmann, M. Rees, Y. Thomann, A. Necola, M. Barbezat, and R. Thomann Composites, Science and Technology, Volume 65, Issue 14 , November 2005, Pages 2259-2268 Abstract: Epoxy-layered silicates nanocomposites based on diglycidyl ether of bisphenol A (DGEBA) and an anhydride-curing agent have been successfully synthesised. A manufacturing process using hand lay-up, vacuum bagging, and hot pressing techniques was developed to produce glass fibre-reinforced laminates with this nanocomposite matrix. Transmission electron microscopy indicated that silicate layers dispersed in the epoxy matrix present a long-range order with an interlamellar spacing of about 9 nm. X-ray diffraction analysis confirmed this nanostructure both in the nanocomposites and in the fibre-reinforced composite based on the same matrix. Scanning electron micrographs of the laminate with a nanocomposite matrix showed that nanolayers are apparently sticking at the surface of the glass fibre, improving possibly in this manner the interfacial properties of the fibres. Flexural testing of the laminates showed that the nanolayers improve the modulus and the strength, respectively, by 6 and 27%. Dynamic mechanical analyses of the epoxy and nanocomposite plates and their corresponding laminates showed a systematic glass transition temperature decrease of the nanocomposite based materials. This explains probably the larger water uptake observed at 50°C in the plate and the laminate based on a nanocomposite matrix as compared with those based on the pristine epoxy. 30: Biodegradable poly(ester hydrazide)s via enzymatic polymerization Metral G, Wentland J, Thomann Y, Tiller JG MACROMOLECULAR RAPID COMMUNICATIONS, Volume: 26, Issue: 16,1330-1335, 2005 Abstract: The reaction of hydrazine with ethyl glycolate results in 1,2-bisglycoylhydrazine, a monomer that was used for the lipase-catalyzed synthesis of biodegradable poly(ester hydrazide)s. The polymers derived from the hydrazide-containing monomer and vinyl-activated adipic, suberic, and sebacic acid, respectively, showed low melting temperatures of 136 to 141 degrees C and are thermally stable up to 300 degrees C. The aliphatic poly(ester hydrazide)s (PEHs) are highly crystalline, as proven by polarization microscopy and atomic force microscopy. Further, the PEHs represent the first described biodegradable poly(hydrazide)s. They degrade in the presence of lipase at 37 degrees within a few weeks.

Publications - Dr. Yi Thomann 2005-2009

52: Gradient Interfaces in SBS and SBS/PS Blends and Their Influence on Morphology Development and Material Properties.
Yi Thomann, Ralf Thomann, Alfred Hasenhindl, Rolf Mülhaupt, Barbara Heck, Konrad Knoll, Helmut Steininger, Kay Saalwächter
Macromolecules 2009, 42(15), 5684-5699.

Abstract: The formation of gradient interfaces between PS- and PB-rich microphases in SBS block copolymers was investigated by means of solid-state NMR and solution NMR as well as TEM, AFM, and SAXS as a function of molecular architecture, comparing linear and star-shaped asymmetric block structures, and gradient as well as random incorporation of styrene comonomer into the PB-rich blocks. Although all studied SBS possess a very similar total styrene content, different morphologies and mechanical properties were found in the extruded SBS/PS blends, whose origin could be related to the formation of a compositional interface gradient. Employing the sensitivity of solid-state NMR for hard (glassy) and soft (rubbery) phases as well as their respective chemical compositions, we found that upon raising the temperature up to the PS glass transition different amounts of polystyrene from the hard PS phase "soften" and integrate into the soft PB-rich phase ("PS softening"). The degree of "PS softening" characterizes the interfacial gradients of SBS block copolymers at elevated temperatures up to the melt. The softened PS was found to partially mix into the soft phase and partially remain at the interface, thus forming different gradient interfaces, depending primarily on the amount of styrene randomly incorporated in the PB mobile blocks and much less on a compositional gradient at the block linkages in SBS chains. In SBS/PS blends, SBS with a substantial "PS softening" effect was found to preferentially form elongated PB lamellar morphologies, which lead to improved mechanical ductility. The purpose of this study was to apply different characterization methods and correlate their results in order to gain important compositional and morphological information as well as their effects on the SBS/PS blend mechanical properties. Rapid and robust low-cost pulsed solid-state NMR methods were established as versatile analytical tools for application in high-output polymer screening (HOPS) and quality control systems, enabling online monitoring of structure-property correlations as well as product quality of SBS-based materials.

51: Column high-temperature gradient adsorption liquid chromatography - a novel way of separation for polyolefins
T. Macko,R. Brüll, Y. Wang, Y. Thomann
The Column (electronic journal), September 4 (2009) 15

50: Separation of propene/1-alkene and ethylene/1-alkene copolymers by high-temperature adsorption liquid chromatography.
Tibor Macko, Robert Bruell, Rufina G. Alamo, Yi Thomann, V. Grumel
Polymer (2009), 50(23), 5443-5448.

Abstract: A high performance liq. chromatog. column (HPLC) Hypercarb packed with porous graphite has proven to discriminate polyolefin mols. due to differences in their adsorption and desorption behavior. While linear polyethylene (PE) and syndiotactic polypropylene (sPP) are adsorbed on the graphite packing, isotactic polypropylene (iPP) is not adsorbed. The column operates at 160 C with 1-decanol as sample solvent and mobile phase. We have now tested this HPLC system for sepns. of random propene/1-alkene and ethylene/1-hexene copolymers: While copolymers of propene with 1-butene, 1-hexene and 1-octene copolymers eluted in size exclusion mode without adsorption, propene/1-octadecene and ethylene/1-hexene copolymers are strongly retained and eluted only after application of a linear gradient starting from 1-decanol and ending with pure 1,2,4-trichlorobenzene. The retention of propene/1-alkene (>11 carbons in the side chain) copolymers increases with the concn. of comonomer, making this HPLC system suitable to sep. these copolymers according to their chem. compn. In contrast, the retention of ethylene/1-hexene samples decreases with increasing 1-hexene content. Branching in this case shortens the length of continuous methylene sequences of the polymer backbone, which are expected to adsorb in a planar conformation to the graphite layers. This is the first report on the sepn. of short chain branched polyolefins by high-temp. adsorption liq. chromatog.

49: Separation of ethylene/1-alkene and propylene/1-alkene copolymers by high-temperature adsorption liquid chromatography.
Tibor Macko, Robert Brull, Rufina Alamo, Yi Thomann
Abstracts of Papers, 238th ACS National Meeting, Washington, DC, United States, August 16-20, 2009

Abstract: Linear low d. polyethylenes (LLDPE) are applied for prodn. of various folies, which are used as packaging materials including short-chain branching into polyethylene or polypropylene enables to modify the phys. properties of resulting copolymers in a wide range. Amt. and distribution of the alkyl groups in the polymer chains play a crucial role. Sepn. based on monitoring of crystallinity of LLDPE, such as TREF and CRYSTAF, are used for study of the branching distribution. We present, as an alternative, chromatog. sepn. of the ethylene/1-alkene and propylene/1-alkene copolymers. Polymer samples are dissolved in a single solvent and injected into a HPLC column at temp. 160 C. Depending on the length of the branches, the copolymers are either eluted or strongly adsorbed. Retained samples are desorbed after application of a solvent gradient. The elution order of both the ethylene/1-alkene and propylene/1-alkene copolymers depend on their chem. compn.

48: Amphiphilic Conetworks Based on End-Linked Multiblock Copolymers of Different Numbers of Blocks and Constant Molecular Weight and Composition
Natalie A. Hadjiantoniou, Costas S. Patrickios, Yi Thomann, Joerg C. Tiller
Macromol. Chem. Phys. 2009, 210, 942-950

Abstract: Amphiphilic conetworks based on end-linked copolymers of the hydrophilic ionizable 2-(dimethylamino)ethyl methacrylate and the hydrophobic n-butyl methacrylate bearing 3, 5, 7, and 9 blocks were synthesized using group transfer polymerization, and employing a bifunctional initiator and sequential addition of monomers and ethylene glycol dimethacrylate cross-linker. All the linear precursors to the conetworks had the same molecular weight and composition, and differed only in their number of blocks. The aqueous degrees of swelling of the ionized conetworks increased with the number of blocks, manifesting the reduction of the driving force for nanophase separation, resulting from the reduction of the length of the hydrophobic segments. Reduction in the tendency for nanophase separation with increasing block number was also supported by atomic force microscopy on bulk conetworks, which indicated a decrease in the domain size as the number of blocks increased.

47: Tailoring of poly(vinyl alcohol) cryogels properties by salts addition.
S. Patachia, C. Florea, C. Friedrich, Y. Thomann
eXPRESS Polymer Letters (2009), 3(5), 320-331

Abstract: Pyrolytic carbon black (PCB) made from used tires was used in ethylene-propylene-diene copolymers (EPDM). The microstructure of PCB was characterized by scanning electron microscopy (SEM). PCB was compounded with EPDM to prepare EPDM vulcanizates. The effects of PCB on the processing properties of EPDM compounds and the mechanical properties of vulcanizates were investigated and compared with other traditional fillers such as semi-reinforcing furnace black (N774), light calcium carbonate (CaCO3) and thermal black (N990). At the same time, the rheological behavior of EPDM compounds filled with different fillers was characterized by capillary rheometrics. The SEM photos showed that the particle shape was quiet different from that of CaCO3 and N990, it was similar to that of N774. The primary particle size was smaller than that of N774, but the aggregate size of PCB was larger than that of N774. The effect of PCB on the processing properties of EPDM compounds was similar to that of other fillers. Among the four fillers, PCB imparted EPDM compounds with higher Mooney viscosity. With the increase of filler content, the scorch time and optimum curing time of EPDM compounds changed little. The reinforcing effect of PCB was similar to that of N990, but inferior to that of N774. With the increase of PCB content, tensile strength, tear strength, and modulus at 100% elongation of EPDM vulcanizates increased significantly. When EPDM was filled with 50 phr PCB, the tear strength of EPDM vulcanizates increased by 3 times, compared with that of EPDM gum vulcanizates. The appearance of EPDM extrudate filled with PCB was coarser than that of other fillers.

46: Correlation between poly(vinyl alcohol) cryogel swelling capacity and synthesis parameters
S.F.C. Patachia, D. Rinja, C. Friedrich, Y. Thomann
Chapter 14 in
"Recent Advances in Research on Biodegradable Polymers and Sustainable Composites: Vol. 3"
Alfonso Jimenez (Herausgeber), Gennady E. Zaikov (Herausgeber)
Nova Science Publishers Inc. (Oktober 2008)

45: A simple nanostructured polymer/ZnO hybrid solar cell - preparation and operation in air
Frederik C. Krebs, Yi Thomann, Ralf Thomann, Jens W. Andreasen
NANOTECHNOLOGY, Volume: 19, Issue: 42, Article Number: 424013, Published: OCT 22 2008

Abstract: A detailed description is given of the preparation of a polymer solar cell and its characterization. The solar cell can be prepared entirely in the ambient atmosphere by solution processing without the use of vacuum coating steps, and it can be operated in the ambient atmosphere with good operational stability under illumination (1000 W m(-2), AM1.5G, 72 +/- 2 degrees C, 35 +/- 5% relative humidity) for 100 h with a 20% loss in efficiency with respect to the initial performance. The dark storability (darkness, 25 degrees C, 35 +/- 5% relative humidity) has been shown to exceed six months without notable loss in efficiency. The devices do not require any form of encapsulation to gain stability, while a barrier for mechanical protection may be useful. The devices are based on soluble zinc oxide nanoparticles mixed with the thermocleavable conjugated polymer poly-(3-(2-methylhexan-2-yl)-oxy-carbonyldithiophene) (P3MHOCT), which through a thermal treatment is converted to the insoluble form poly(3-carboxydithiophene) (P3CT) that generally gives stable polymer solar cells. The devices employed a solution based silver back electrode. One advantage is that preparation of the devices is very simple and can be carried out by hand under ambient conditions, requiring only a hot plate that can reach a temperature of 210 degrees C, and preferably also a spincoater. This type of device is thus excellently suited for teaching and demonstration purposes provided that the materials are at hand.

44: Boehmite nanorod-reinforced-polyethylenes and ethylene/1-octene thermoplastic elastomer nanocomposites prepared by in situ olefin polymerization and melt compounding.
TS. Halbach, Y.Thomann, R. Mülhaupt
JOURNAL OF POLYMER SCIENCE PART A-POLYMER CHEMISTRY, 46, 8, 2755-2765, 2008

Abstract: Nanocomposites of polyethylene (HDPE) and poly(ethylene-co-1-octene) thermoplastic elastomers, both containing boehmites with variable sizes, shapes, and aspect ratios (1-20), were prepared by means of in situ olefin polymerization and melt compounding. The in situ olefin polymerization in the presence of boehmite nanorods afforded nanocomposites containing 4-8 wt % of boehmite. In an alternative process, the in situ olefin polymerization was used to produce polyolefins with high boehmite content of 50 wt % as masterbatches for polyolefin melt compounding with ethylene homo- and copolymers. The addition of the boehmite nanofillers improved the stiffness without sacrificing high elongation at break. The stiffness, as expressed by Young's modulus, increased with increasing boehmite aspect ratio. In case of thermoplastic elastomer nanocomposites the increase of stiffness was accompanied by a simultaneous increase of elongation at break. According to transmission electron microscopy (TEM), fine dispersion of the polar boehmite nanorods and nanoplatelets within the nonpolar hydrocarbon polymer matrix was obtained without requiring the addition of special dispersing agents or functionalized polyolefin compatibilizers. The comparison of melt compounding of polyethylene with boehmites or polyethylene/boehmite masterbatches revealed that compounding of masterbatches prepared by in situ polymerization filling afforded much finer and more uniform nanoboehmite dispersions.

43: Direct Observation of Interphase Composition in Block Copolymers.
Saalwächter, Kay; Thomann, Yi; Hasenhindl, Alfred; Schneider, Horst.
Macromolecules (2008), 41(23), 9187-9191.

Abstract: We demonstrate the fast, direct, and quant. observation of temp.- and comonomer-induced changes in the interfacial size and compn. in phase-sepd. styrene-butadiene-styrene block copolymers by double-quantum-filtered proton spin-diffusion NMR expts. performed under high-resoln. magic-angle spinning conditions. The expt. is based on the dipolar-mediated diffusion of spin magnetization from the (styrenic) rigid phase through a more mobile interphase of variable size and compn. into the soft (polybutadiene) domain. The expt. spectroscopically distinguishes between mobilized styrene segments located in the interphase and those mixed (dissolved) in the bulk of the mobile domain. The results indicate that temp.-induced softening due to mobilization of styrene units at the interface and the tendency to become part of an extended interphase is stronger for systems with a lower segregation strength, having statistically distributed styrene comonomers in the soft domain.

42: Structural characterization of glassy and rubbery model anionic amphiphilic polymer conetworks.
Kali, Gergely; Georgiou, Theoni K.; Ivan, Bela; Patrickios, Costas S.; Loizou, Elena; Thomann, Yi; Tiller, Jörg C.
ACS Symposium Series (2008), 996, 286-302.

Abstract: The structure of two series of model amphiphilic polymer conetworks based on the hydrophilic anionic methacrylic acid was characterized by at. force microscopy (AFM) and small-angle neutron scattering (SANS). In the first series, the hydrophobic component was the glassy poly(Me methacrylate), while the rubbery poly(2-butyl-1-octyl methacrylate) constituted the hydrophobic segments in the second series. Each series comprised conetworks in which the hydrophile / hydrophobe ratio was systematically varied as well as conetworks with different architecture of the linear chain: ABA and BAB triblock and statistical. The AFM and SANS measurements indicated nanophase sepn. in the triblock copolymer-based conetworks and provided the spacing, size and shape of the formed nanodomains.

41: Spin-diffusion NMR at low field for the study of multiphase solids.
Mauri, M.; Thomann, Y.; Schneider, H.; Saalwaechter, K.
Solid State Nuclear Magnetic Resonance (2008), 34(1-2), 125-141.

Abstract: The use of spin-diffusion NMR for the measurement of domain sizes in multiphase materials is becoming increasingly popular, in particular for the study of heterogeneous polymers. Under conditions where T 1 relaxation can be neglected, which is mostly the case at high field, anal. and approx. solns. to the evolution of spin diffusion are available. In order to extend the technique to more general conditions, we performed a comprehensive study of the diffusion of magnetization in a model copolymer at low field, where T 1 tends to be of the same order of magnitude as the typical spin-diffusion time. In order to study the effects of T 1 and to delineate the optimal T 1 values for back correction prior to applying the initial-rate approxn., we developed a numerical simulation based on the diffusion equation and including longitudinal relaxation. We present and discuss the limits of simple correction strategies for initial-slope anal. based on apparent relaxation times from satn.-recovery expts. or the spin-diffusion expts. themselves. Our best strategy faithfully reproduces domain sizes obtained by both TEM investigations and full simultaneous fitting of spin-diffusion and satn.-recovery curves. Full fitting of such independent data sets not only yields correct domain sizes, but also the true longitudinal relaxation times, as well as spin-diffusion coeffs. Effects of interphases with distinct mobility on spin-diffusion curves, as well as practical hints concerning the reliable component decompn. of the detected low-resoln. FID signal by help of different magnetization filters are also discussed in detail.

40: Acrylic nanocomposite resins for use in stereolithography and structural light modulation based rapid prototyping and rapid manufacturing technologies.
Gurr, Matthias; Hofmann, Daniel; Ehm, Michael; Thomann, Yi; Kübler, Rainer; Mülhaupt, Rolf.
Advanced Functional Materials (2008), 18(16), 2390-2397.

Abstract: A novel family of optically transparent acrylic nanocomposites contg. up to 30 wt % silica nanoparticles with an av. diam. of 20 nm was developed for application in structural light modulation (SLM) and stereolithog. (SL) technologies. The uniform dispersion of nanoparticles affords a significantly improved toughness/stiffness-balance of the photopolymd. and postcured nanocomposites. It is possible to increase stiffness, as expressed by Young's modulus, from 1290 to 1700 MPa without encountering the embrittlement typical for many other conventional filled polymers. Fracture behavior is examd. by means of fracture mechanics investigation and SEM analyses of fracture surfaces. According to TEM analyses and measurement of optical transmittance remarkable uniform dispersion of silica nanoparticles was achieved. The silica nanoparticle concns. up to 17 wt % give only marginally higher viscosities and do not affect transmittance, while slightly increasing the exposure times needed in photopolymn. Moreover, the silica nanoparticles afford materials with reduced shrinkage and improved properties. The green effective ankle splay out (EASO) measured on H-shaped diagnostic specimens, is significantly reduced for the nanocomposite materials from 1.38 mm for the unfilled material to 0.82 mm for nanocomposites contg. 30 wt % nanosilica. The building accuracy is increased significantly with increasing content of silica nanofillers.

39: Nanophase Separated Anionic Amphiphilic Model Polymer Conetworks Based on Methacrylic acid
G. Kali, T.K. Georgiou, B. Ivan, C.S. Patrickios, E. Loizou, Y. Thomann and J. Tiller
NSTI Nanotech 2007, Nanotechnology Conference and Trade Show, Santa Clara, CA, United States, May 20-24, 2007, 2, 60-63.

Abstract: Two series of model amphiphilic polymer conetworks were synthesized by group transfer polymerization (GTP). The first one was composed of the hydrophobic methyl methacrylate (MMA) and the hydrophilic methacrylic acid (MAA), and the second one contained 2-butyl-1-octyl methacrylate (BOMA) as the hydrophobic monomer and MAA. Anionic amphiphilic model conetworks and the BOMA monomer were synthesized and investigated for the first time. The network synthesis was performed by sequential monomer/cross-linker additions to form conetwork series in a wide range of composition and architecture. All conetwork precursors and the extractables were characterized by gel permeation chromatography and nuclear magnetic resonance spectroscopy to determine the molecular weights and compositions, respectively. The polymer conetworks were investigated in terms of their degree of swelling in aqueous media and in THF. The thermal and mechanical properties were determined by differential scanning calorimetry and dynamic mechanical analyses, respectively. These results indicate the differences between the MMA and BOMA conetwork series. The nanophase separated structure was proved by atomic force microscopy (AFM) and small angle neutron spectroscopy (SANS) for the triblock copolymer model conetworks but not for the networks with random monomer distributions.

38: Synthesis and Characterization of Anionic Amphiphilic Model Conetworks of 2-Butyl-1-Octyl-Methacrylate and Methacrylic Acid: Effects of Polymer Composition and Architecture.
Kali, Gergely; Georgiou, Theoni K.; Ivan, Bela; Patrickios, Costas S.; Loizou, Elena; Thomann, Yi; Tiller, Jörg C.
Langmuir (2007), 23(21), 10746-10755.

Abstract: Seven amphiphilic conetworks of methacrylic acid (MAA) and a new hydrophobic monomer, 2-butyl-1-octyl-methacrylate (BOMA), were synthesized using group transfer polymn. The MAA units were introduced via the polymn. of tetrahydropyranyl methacrylate (THPMA) followed by the removal of the protecting tetrahydropyranyl group by acid hydrolysis after network formation. Both THPMA and BOMA were inhouse synthesized. Ethylene glycol dimethacrylate (EGDMA) was used as the cross-linker. Six of the conetworks were model conetworks, contg. copolymer chains between cross-links of precise mol. wt. and compn. The prepd. conetwork series covered a wide range of compns. and architectures. In particular, the MAA content was varied from 67 to 94 mol %, and three different conetwork architectures were constructed: ABA triblock copolymer-based, statistical copolymer-based, and randomly cross-linked. The linear conetwork precursors were analyzed by gel permeation chromatog. and 1H NMR spectroscopy in terms of their mol. wt. and compn., both of which were found to be close to the theor. calcd. values. The degrees of swelling (DS) of all the amphiphilic conetworks were measured in water and in THF over the whole range of ionization of the MAA units. The DSs in water increased with the degree of ionization (DI) and the content of the hydrophilic MAA units in the conetwork, while the DSs in THF increased with the d.p. of the chains between the cross-links and by reducing the DI of the MAA units. Finally, the nanophase behavior of the conetworks was probed using small-angle neutron scattering and at. force microscopy.

37: Structural characterization of glassy and rubbery anionic amphiphilic model conetworks.
Kali, Gergely; Georgiou, Theoni K.; Ivan, Bela; Patrickios, Costas S.; Loizou, Elena; Thomann, Yi; Tiller, Jörg
Abstracts of Papers, 233rd ACS National Meeting, Chicago, IL, United States, March 25-29, 2007

Abstract: The structure of two series of amphiphilic model conetworks based on the hydrophilic anionic methacrylic acid was characterized by at. force microscopy (AFM) and small-angle neutron scattering (SANS). In the first series the hydrophobic component was the glassy poly(Me methacrylate), while the rubbery poly(2-butyl-1-octyl methacrylate) constituted the hydrophobic segments in the second series. Each series comprised conetworks in which the hydrophile / hydrophobe ratio was systematically varied as well as conetworks with different architecture of the linear chain: ABA and BAB triblock and statistical. The measurements indicated nanophase sepn. in the triblock copolymer-based conetworks and provided the spacing, size and shape of the formed nanodomains.

36: Synthesis and Characterization of Anionic Amphiphilic Model Conetworks Based on Methacrylic Acid and Methyl Methacrylate: Effects of Composition and Architecture.
Kali, Gergely; Georgiou, Theoni K.; Ivan, Bela; Patrickios, Costas S.; Loizou, Elena; Thomann, Yi; Tiller, Joerg C.
Macromolecules, (2007), 40(6), 2192-2200.

Abstract: A series of amphiphilic conetworks of methacrylic acid (MAA) and Me methacrylate (MMA) were synthesized using group transfer polymn. (GTP). The MAA units were introduced via the polymn. of tetrahydropyranyl methacrylate (THPMA), followed by the removal of the protecting tetrahydropyranyl group by acid hydrolysis after network formation. 1,4-Bis(methoxytrimethylsiloxymethylene)cyclohexane (MTSCH) was used as a bifunctional GTP initiator, while ethylene glycol dimethacrylate (EGDMA) served as the cross-linker. Nine of the conetworks were model conetworks, comprising copolymer chains between the cross-links of precise mol. wt. and compn. Eight of the model conetworks were based on ABA triblock copolymers, while the ninth was based on a statistical copolymer. The tenth conetwork was not model but randomly cross-linked. The mol. wt. and the compn. of the linear conetwork precursors were analyzed by gel permeation chromatog. and 1H NMR, resp., and were found to bear values close to the theor. expected. FTIR spectroscopic analyses indicated complete polymn. of the EGDMA crosslinker vinyl units and complete hydrolysis of the THPMA units. The degrees of swelling (DS) of all the conetworks were measured in water and in THF as a function of the degree of ionization (DI) of the MAA units. The DSs in water increased with the DI of the MAA units (and the pH), while the DSs in THF presented the opposite trend. Finally, small-angle neutron scattering and at. force microscopy confirmed nanophase sepn. in a triblock copolymer-based model conetwork and lack of it in its statistical copolymer counterpart.

35: Iridescent Colors from Films Made of Polymeric Core-Shell Particles
He, Xu; Thomann, Yi; Leyrer, Reinhold J.; Rieger, Jens.
Polymer Bulletin, (2006), 57(5), 785-796.

Abstract: Brilliant and angle-dependent iridescent color films were obtained from polymer films produced via colloidal crystn. of monodisperse core-shell particles by drying aq. dispersions. The core is a styrene copolymer and the shell is a Me methacrylate copolymer. Through variation of the particle size, the brilliant color could be varied throughout the visible spectrum. The color effects of the smooth thin films exhibit excellent thermal and water stability. The morphol. of the core-shell particles and the properties of the corresponding films were characterized by dynamic light scattering (DLS), at. force microscopy (AFM), differential scanning calorimetry (DSC), and reflection spectrum measurements. The brightness of the film is strongly dependent on size and quality of the cryst. domains.

34: Living random and block copolymerization of ethene and propene on a tailor-made phenoxyimine catalyst and characterization of the resulting high molecular weight PE-block-P(E-co-P) block copolymers.
Weiser, Marc-Stephan; Thomann, Yi; Heinz, Lars-Christian; Pasch, Harald; Mülhaupt, Rolf.
Polymer (2006), 47(13), 4505-4512.

Abstract: The phenoxyimine catalyst (bis(N-(3',5'-diiodo-salicylidene)-2,6-difluoroaniline)-titanium(IV)-dichloride) was tailored to enable random and block copolymn. of propylene and ethylene with compns. covering the entire feasible compn. range. Well-defined high mol. wt. diblock copolymers of the type PE-block-P(E-co-P), consisting of a semi-cryst. polyethylene and a soft P(E-co-P) block, were prepd. and evaluated with respect to propylene content and the block lengths. The characterization by means of AFM, CRYSTAF data and high temp. chromatog. elution provided the exptl. evidence that no homo-polyethylene and less than 5% of the random copolymer are formed as byproducts.

33: PMMA Gradient Materials and in situ Nanocoating via Self-Assembly of Semifluorinated Hyperbranched Amphiphiles
Yi Thomann, R. Haag, R. Brenn, R. Delto, H. Weickman, R. Thomann, R. Mülhaupt.
Macromol. Chem. Phys. 2005, 206, 134-141

Abstract: Nanostructured poly(methyl methacrylate) (PMMA) gradient materials with in situ nanocoating were obtained via self-assembly of semifluorinated hyperbranched polyglycerol amphiphiles (FPG) at the PMMA surface during free-radical MMA bulk polymerisation. The FPG was designed as novel nanoadditive and prepared by etherification of the hydrophilic hyperbranched polyglycerol core with allylether and subsequent quantitative addition of the hydro- and oleophobic 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluoro-octane-1-thiol to the double bond end groups. As a result of the FPG self-assembly, a fluorine-containing nanocoating, with an average thickness of 150 to 200 nm at the PMMA surface, was detected by transmission electron microscopy (TEM) and Rutherford backscattering spectrometry (RBS) of an 4He+ beam. The resulting nanocoating formation was driven by the interactions of the perfluorohexyl end groups and the in situ phase separation with increasing conversion of the MMA polymerisation. The FPG nanocoating consisted of a nanolayered substructure composed of alternating fluorine-containing and fluorine-free layers with an average thickness of 3-5 nm, which was evidenced by atomic force microscopy (AFM) and small angle X-ray scattering (SAXS). Very small amounts of the FPG amphiphile, typically less than 3 wt.-% added to PMMA, were found to be sufficient to achieve the in situ nanocoating formation at the PMMA surface. The surfaces of the PMMA/FPG surface gradient materials were water and oil repellent.

32: Nanophase Separated Amphiphilic Microbeads.
Savin, Gabriela; Bruns, Nico; Thomann, Yi; Tiller, Jörg C.
Macromolecules (2005), 38(18), 7536-7539.

Abstract: Nanostructured nonporous amphiphilic polymeric microbeads and their evaluation as catalyst support. A hydrophobic polymeric crosslinker, a,w-methacrylate-terminated poly(dimethylsiloxane), MA-PDMS-MA, was copolymd. with trimethylsilylated 2-hydroxyethyl acrylate (TMSOEA) using photoinitiator Irgacure 651 in a surfactant soln. and phosphate buffer, irradiated at 340 nm for 3 min to yield a hydrophobic precursor network. Upon subsequent cleavage of the TMS groups, an amphiphilic, nanophase sepd. network formed. The type of surfactant used as emulsifier in polymn. has an important effect on compn. and morphol. of the microbeads. A dispersion of spherical polymer particles showing phase sepd. bulk morphol. was obtained. The amphiphilic polymer microbeads show a continuous nanostructure from the inside to the surface, the PHEA segments form a sponge-like continuous phase with domain size of about 3-6 nm and the PDMS domains (18-30 nm) are embedded into the PHEA structure. The amphiphilic PHEA-l-PDMS microbeads were evaluated as phase transfer matrix for catalysis, in a-chymotrypsin (CT) catalyzed transesterification of N-acetyl-L-phenylalanine Et ester (APEE) with propanol in n-octane to N-acetyl-L-phenylalanine Pr ester (APPE).

31: Epoxy-layered silicate nanocomposites as matrix in glass fibre-reinforced composites
X. Kornmann, M. Rees, Y. Thomann, A. Necola, M. Barbezat, and R. Thomann
Composites, Science and Technology, Volume 65, Issue 14 , November 2005, Pages 2259-2268

Abstract: Epoxy-layered silicates nanocomposites based on diglycidyl ether of bisphenol A (DGEBA) and an anhydride-curing agent have been successfully synthesised. A manufacturing process using hand lay-up, vacuum bagging, and hot pressing techniques was developed to produce glass fibre-reinforced laminates with this nanocomposite matrix. Transmission electron microscopy indicated that silicate layers dispersed in the epoxy matrix present a long-range order with an interlamellar spacing of about 9 nm. X-ray diffraction analysis confirmed this nanostructure both in the nanocomposites and in the fibre-reinforced composite based on the same matrix. Scanning electron micrographs of the laminate with a nanocomposite matrix showed that nanolayers are apparently sticking at the surface of the glass fibre, improving possibly in this manner the interfacial properties of the fibres. Flexural testing of the laminates showed that the nanolayers improve the modulus and the strength, respectively, by 6 and 27%. Dynamic mechanical analyses of the epoxy and nanocomposite plates and their corresponding laminates showed a systematic glass transition temperature decrease of the nanocomposite based materials. This explains probably the larger water uptake observed at 50°C in the plate and the laminate based on a nanocomposite matrix as compared with those based on the pristine epoxy.

30: Biodegradable poly(ester hydrazide)s via enzymatic polymerization
Metral G, Wentland J, Thomann Y, Tiller JG
MACROMOLECULAR RAPID COMMUNICATIONS, Volume: 26, Issue: 16,1330-1335, 2005

Abstract: The reaction of hydrazine with ethyl glycolate results in 1,2-bisglycoylhydrazine, a monomer that was used for the lipase-catalyzed synthesis of biodegradable poly(ester hydrazide)s. The polymers derived from the hydrazide-containing monomer and vinyl-activated adipic, suberic, and sebacic acid, respectively, showed low melting temperatures of 136 to 141 degrees C and are thermally stable up to 300 degrees C. The aliphatic poly(ester hydrazide)s (PEHs) are highly crystalline, as proven by polarization microscopy and atomic force microscopy. Further, the PEHs represent the first described biodegradable poly(hydrazide)s. They degrade in the presence of lipase at 37 degrees within a few weeks.