Doris Pospiech

Leibniz Institute of Polymer Research

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Dieter Jehnichen

Leibniz Institute of Polymer Research

Liane Häußler

Leibniz Institute of Polymer Research

Brigitte Voit

Leibniz Institute of Polymer Research

Hartmut Komber

Leibniz Institute of Polymer Research

Peter Friedel

Leibniz Institute of Polymer Research

Andreas Janke

Leibniz Institute of Polymer Research

Volker Altstädt

University of Bayreuth

Kathrin Eckstein

University of Tübingen

Andreas Korwitz

Leibniz Institute of Polymer Research

Manfred Döring

Fraunhofer Institute for Structural Durability and System Reliability

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Leibniz Institute of Polymer Research

153

TU Dresden

Leibniz Association

Leibniz Institute for Neurobiology

University of Bayreuth

Universität Hamburg

Federal Institute For Materials Research and Testing

Polytechnic University of Turin

Russian Academy of Sciences

Centre National de la Recherche Scientifique

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Semifluorinated Methacrylate Random Copolymers: Phase Transitions and Molecular Dynamics

Molecular Crystals and Liquid Crystals (2015)

Sotiria Kripotou C. Pandis Apostolos Kyritsis Doris Pospiech Dieter Jehnichen

Random copolymers of methyl methacrylate (MMA) and sermifluorinated methacrylate (sfMA), with constant side chain length (H10F10), as comonomers and various sfMA molar contents were studied by Dielectric Relaxation Spectroscopy (DRS) technique with respect to their phase transitions and molecular dynamics. DRS technique was proven a suitable technique for the detection of the phase transitions that take place in the systems under investigation, as it follows from the comparison with Differential Scanning Calorimetry (DSC) technique, which is traditionally used. Regarding molecular mobility, molecular motions of both the main chain and the sf side chains were followed, while different dynamics was recorded depending on the structure of the copolymers.

Side chain

10.1080/15421406.2015.1027992

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Fiber formation and properties of polyester/lignin blends

Journal of Applied Polymer Science (2019)

Doris Pospiech Andreas Korwitz Kathrin Eckstein Hartmut Komber Dieter Jehnichen

ABSTRACT Thermotropic liquid crystalline polyesters with varied chemical structure are synthesized by melt transesterification polycondensation. They are employed as matrix for blends with lignin materials to obtain melt‐spinnable precursors for carbon fibers. The lignin samples are carefully purified by fractionation, enzymatic removal of reducing sugars, and subsequent modification of the terminal OH groups. Effective melt blending is achieved with liquid‐crystalline aromatic–aliphatic polyesters having melting ranges that match the softening temperature of the lignin fractions, which is necessary to prevent thermal decomposition of the lignin. Polyester/lignin blends are partially compatibilized, phase‐separated materials. The polyester/lignin materials are melt‐spun successfully. The fiber properties depend on the lignin purification process. X‐ray scattering reveals that orientation in lignin‐containing fibers is maintained. First experiments show that the fibers can be converted successfully to carbon fibers by thermal annealing procedures. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136 , 48257.

Copolyester

Thermotropic crystal

10.1002/app.48257

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Citations (8)

Surface patterning of methaacrylate-based films.

Paola Fabbri Massimo Messori Maurizio Toselli F. Pilati S. Ptacek

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Synthesis of Fluorinated Hyperbranched Polymers and Their Use as Additives in Cationic Photopolymerization

Macromolecular Materials and Engineering (2005)

Marco Sangermano Anna Di Gianni Roberta Maria Bongiovanni Aldo Priola Brigitte Voit

Abstract Summary: A fluorine containing hyperbranched polymer was synthesized by modifying an aromatic‐aliphatic hyperbranched polyester with a semifluorinated alcohol via a Mitsunobu reaction and was subsequently used as an additive in cationic photopolymerization of an epoxy resin. The remaining OH groups of the fluorinated hyperbranched polymer interact with the polymeric carbocation through a chain‐transfer mechanism inducing an increase in the final epoxy conversion. The fluorinated HBP induces modification of bulk and surface properties, with an increase in T g and surface hydrophobicity already reached at very low concentration. The HBFP additive can, therefore, protect the coatings from aggressive solvents, increases hardness, and allows the preparation of a low energy surface coating. Synthesis of fluorinated hyperbranched polyester. magnified image Synthesis of fluorinated hyperbranched polyester.

Cationic polymerization

Carbocation

Surface Modification

10.1002/mame.200500048

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Citations (37)

Methacrylate Copolymers with Liquid Crystalline Side Chains for Organic Gate Dielectric Applications

ACS Applied Materials & Interfaces (2014)

Andreas Berndt Doris Pospiech Dieter Jehnichen Liane Häußler Brigitte Voit

Polymers for all-organic field-effect transistors are under development to cope with the increasing demand for novel materials for organic electronics. Besides the semiconductor, the dielectric layer determines the efficiency of the final device. Poly(methyl methacrylate) (PMMA) is a frequently used dielectric. In this work, the chemical structure of this material was stepwise altered by incorporation of cross-linkable and/or self-organizing comonomers to improve the chemical stability and the dielectric properties. Different types of cross-linking methods were used to prevent dissolution, swelling or intermixing of the dielectric e.g. during formation processes of top electrodes or semiconducting layers. Self-organizing comonomers were expected to influence the dielectric/semiconductor interface, and moreover, to enhance the chemical resistance of the dielectric. Random copolymers were obtained by free radical and reversible addition-fragmentation chain transfer (RAFT) polymerization. With 6-[4-(4'-cyanophenyl)phenoxy]alkyl side chains having hexyl or octyl spacer, thermotropic liquid crystalline (LC) behavior and nanophase separation into smectic layers was observed, while copolymerization with methyl methacrylate induced molecular disorder. In addition to chemical, thermal and structural properties, electrical characteristics like breakdown field strength (EBD) and relative permittivity (k) were determined. The dielectric films were studied in metal-insulator-metal setups. EBD appeared to be strongly dependent on the type of electrode used and especially the ink formulation. Cross-linking of PMMA yielded an increase in EBD up to 4.0 MV/cm with Ag and 5.7 MV/cm withPSS electrodes because of the increased solvent resistance. The LC side chains reduce the ability for cross-linking resulting in decreased breakdown field strengths.

Chain transfer

Side chain

Dielectric strength

10.1021/am5069479

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Citations (17)

Inverse gas chromatographic study of some polyethers

Polymer (1999)

F. Dieckmann Doris Pospiech Petra Uhlmann Frank Böhme H. R. Kricheldorf

Polysulfone

Inverse gas chromatography

10.1016/s0032-3861(98)00321-8

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Citations (10)

Conformational properties of macromolecules of heterocyclic polyester imides in dilute dichloroacetic acid solutions

Journal of Polymer Science Part B Polymer Physics (2003)

Л. Н. Андреева S.V. Bushin V.N. Tsvetkov E. V. Belyaeva V. V. Il’in

Abstract Several series of polyester imides (PEIs) were prepared by melt polycondensation of trimellitimidobenzoic acid and acetylated, substituted hydroquinones as well as by solution polycondensation of corresponding dichlorides with hydroquinones. The influence of either phenyl‐ or tert ‐butyl substituents at the hydroquinone unit on the hydrodynamic (diffusion and viscometry) and optical [flow (FB) and electrical (EB) birefringence] properties of solutions of these PEIs were investigated. Independent methods for quantitative evaluation of the length of the statistical Kuhn segment A gave values of 14.5 nm (translational friction and electrical birefringence) and 12.0 nm (flow birefringence), respectively. The equilibrium rigidity of PEIs with phenyl and tert ‐butyl lateral substituents at the para‐aromatic chain fragment was comparable. Conformational properties of the PEIs were analyzed, and the conjugation energies of the ester and amide groups for para‐aromatic polyesters, PEIs, and structurally similar polyamidobenzoxazoles and polyamidobenzimidazoles were compared. The introduction of the phthalimide ring leads to a decrease of conjugation energy and deviation of the ester group from coplanarity. The Kuhn segment values obtained were useful for calculations of phase diagrams of semiflexible segmented block copolymers. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 12–24, 2004

Flow birefringence

Amide

10.1002/polb.10667

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Citations (1)

Intercalation degree in PP/organoclay nanocomposites: role of surfactant structure

Polymers for Advanced Technologies (2008)

Felipe Silva Bellucci Andrea Terenzi Andreas Leuteritz Doris Pospiech Alberto Frache

Abstract The formation of exfoliated polymer–clay nanocomposites depends upon several factors such as the nature of the polymer, the nature of the clay, as well as the type, packing density, and size of the organic modifier on the silicate layers. The main aim of this work was focused on the role of the chemical structure of the organic modifier on the intercalation properties of the organo‐modified clay into non‐polar polymer matrices such as a polypropylene homopolymer. To achieve this purpose organo‐montmorillonites containing different loadings of organic modifier with increasing molar volume were prepared and used to produce PP based nanocomposites. Morphology studies performed on the composites pointed out that two distinct aspects have to be considered for organic modification of the clays: the interlayer distance and the degree of the inorganic surface coverage, which are the main driving forces for the intercalation process. It was found that an intercalated structure was reached when either a large non‐polar molecule, which ensures an optimal interlayer distance with a partial surface coverage or a mixture of small and large molecules leading to a slightly lower interlayer distance but to a higher surface coverage degree was used. Moreover, rheological, mechanical, and thermal studies indicated that the degree of dispersion and interaction between clay platelets and the polymer chains strongly depended on the interlayer spacing and clay surface coverage. Copyright © 2008 John Wiley & Sons, Ltd.

Organoclay

Polypropylene

Polymer clay

10.1002/pat.1101

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Citations (24)

Properties of Segmented Block Copolymers in PEEK/PSU Blends

High Performance Polymers (2007)

Thorsten Hoffmann Doris Pospiech Liane Häußler Petra Pötschke Uta Reuter

As a method of compatibilization of immiscible polyether ether ketone (PEEK)/polysulfone (PSU) blends, the addition of segmented PEEK/PSU block copolymers based on amorphous bisphenol A-containing PEEK was studied. This approach was evaluated for blends consisting of PEEK and PSU homopolymers with different molecular weights and different amounts of compatibilizers (segmented PEEK/PSU block copolymers and reactive end-functionalized PEEK and PSU oligomers). The compatibilizers were added under varying melt-processing conditions and effectively allowed the homopolymers to interact with the segmented block copolymers in the blend. The influence of the compatibilizers on the phase behavior was examined in both binary and ternary blends. Interactions in the amorphous phase, which effectively induce an enhancement of the toughness properties of the final product, could be detected.

Compatibilization

Polysulfone

Miscibility

10.1177/0954008307082176

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Citations (13)

Raspberry-like Pt clusters with controlled spacing produced by deposition of loaded block copolymer micelles from supercritical CO2

European Polymer Journal (2015)

Dmitry O. Kolomytkin Igor V. Elmanovich S. S. Abramchuk Larisa Tsarkova Doris Pospiech

Deposition

10.1016/j.eurpolymj.2015.07.048

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Citations (4)