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dc.contributor.advisor Vana, Philipp Prof. Dr.
dc.contributor.author Hendrich, Michael
dc.date.accessioned 2016-12-13T09:04:05Z
dc.date.available 2016-12-13T09:04:05Z
dc.date.issued 2016-12-13
dc.identifier.uri http://hdl.handle.net/11858/00-1735-0000-002B-7CD8-0
dc.language.iso eng de
dc.publisher Niedersächsische Staats- und Universitätsbibliothek Göttingen de
dc.rights.uri http://creativecommons.org/licenses/by-nc-nd/4.0/
dc.subject.ddc 540 de
dc.title Biomimetic Polymer Systems via RAFT Polymerization - Routes to High-Performance Materials de
dc.type doctoralThesis de
dc.contributor.referee Vana, Philipp Prof. Dr.
dc.date.examination 2016-12-02
dc.description.abstracteng Nature provides numerous examples of structural materials with outstanding mechanical properties. An especially intriguing material is spider dragline silk that outmatches man-made high-performance fibers such as Kevlar or high-tensile steel. Therefore, it has been a prolific source of inspiration to research in various scientific fields. In this thesis, the macromolecular structure of spider dragline silk was adapted by preparation of multiblock copolymers with hydrogen bonding domains, and soft, amorphous segments, and their mechanical performance was evaluated via tensile testing. The multiblock copolymer structure was achieved by the use of polyfunctional RAFT (reversible addition−fragmentation chain transfer) agents with trithiocarbonate groups acting as junction points between individual blocks. For comparison, triblock copolymers were prepared with similar block lengths and composition. It was found that the multiblock copolymers show superior mechanical performance, exibiting higher elasticity, tensile strength and toughness. After initial tensile testing and failure of test specimens, samples of both tri- and multiblock copolymers could be regenerated via thermal annealing. Then, significantly enhanced sample toughness was observed which indicated an increased number of hydrogen bonding interactions. In order to expand the scope of polyfunctional RAFT agents for tailored material design, the RAFT polymerization of polyfunctional trithiocarbonates was explored in closer detail. During polymerization, RAFT groups being connected to polymer segments are redistributed between macromolecular chains and a characteristic distribution of RAFT groups in the polymer is obtained. This concept was used for the preparation of polystyrene samples by mixing a bi- and a polyfunctional RAFT agent in specific ratios. By characterizing the prepared samples via size-exclusion chromatography (SEC) it could be demonstrated, that the resulting molar mass and hence the number of RAFT groups per macromolecule can be tailored.To exploit this concept for advanced material design, star-shaped RAFT agent was mixed with polyfunctional RAFT agent and multiblock copolymers of styrene and n-butyl acrylate were prepared that exhibited the star-shaped topological features. The mechanical properties of the prepared materials were investigated via tensile testing. Compared with multiblock copolymers obtained from pure polyfunctional RAFT agents, significantly improved material toughness was observed for the materials that were prepared using the novel mixing approach. Additionally, strain whitening of polymer samples could be prevented and it was demonstrated, that the mixing approach yields materials with superior toughness than conventional blends of star and multiblock copolymers. In conclusion, this work could demonstrate excellent versatility of polyfunctional RAFT agents for the preparation of highperformance materials. de
dc.contributor.coReferee Samwer, Konrad Prof. Dr.
dc.contributor.thirdReferee Geil, Burkhard Prof. Dr.
dc.contributor.thirdReferee Buback, Michael Prof. Dr.
dc.contributor.thirdReferee Ehlers, Florian Dr.
dc.contributor.thirdReferee Zeuch, Thomas PD Dr.
dc.subject.eng Biomimetic Polymers de
dc.subject.eng Spider Dragline Silk de
dc.subject.eng RAFT Polymerization de
dc.subject.eng Mechanical Properties de
dc.identifier.urn urn:nbn:de:gbv:7-11858/00-1735-0000-002B-7CD8-0-6
dc.affiliation.institute Fakultät für Chemie de
dc.subject.gokfull Chemie  (PPN62138352X) de
dc.identifier.ppn 874847885

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