Bio-inspired Polymer Material Design via RAFT Polymerization.
Final Report Abstract
In this project, well-defined macromolecules with moieties that undergo strong hydrogen bondings (HB) were designed, which show enhanced mechanical properties due to their directed micro- and nano-structuring. Two bio-inspired principles were translated into synthetic materials: First, repetitive peptide sequences that fold into regular structural elements via HB were mimicked by triand multiblock copolymers containing blocks carrying HB motifs. The process of forming multiblock copolymers via RAFT polymerization using polyfunctional RAFT agents was extensively explored and optimized. The resulting materials display largely increased energy dissipation mechanisms under mechanical stress and a very strong healing effect. Multiblock samples display a larger toughness than corresponding triblock samples. We could demonstrate that a small content of only 0.1 mol-% of HB-monomer improves the mechanical properties of these thermoplastic elastomers significantly. Secondly, incorporating ring-shaped structures into the synthetic polymer chain mimicked reversible unfolding of HB-stabilized modules that have been observed in the skeletal muscle protein titin. For this purpose, a ring polymer carrying HB motifs for internal stabilization was designed as functional polymer module. The ring polymers were formed via ring-expansion polymerization, which was extensively explored and optimized. Mechanistic features of the process, such as ring-merging reactions, were exploited for directed increase of functionalities per ring unit. The rings were interlinked to polycyclic materials, which show a distinctive stress-strain behavior that is similar to biological materials. Fracture stress and toughness is significantly increased with these polymers. Additionally, the new materials show a shape-memory behavior with good shape recovery after deformation and also have healing abilities due to its inherent ability to form hydrogen bonds.
Publications
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‘Ideal Molecular Weight Distributions of Multiblock Copolymers Prepared via RAFT Polymerization’. Macromolecules, 2010, 43, 10283- 10290
B. Ebeling, M. Eggers, and P. Vana
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‘H-bonding in Polymers from RAFT Polymerization’. Polymer Preprints, 2011, 52, 421-422
R. Rotzoll, J.-H. Schuetz, M. Schwabe, K. Samwer, and P. Vana
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‘Multiblock Copolymers of Styrene and Butyl Acrylate via Polytrithiocarbonate-Mediated RAFT Polymerization’. Polymers 2011, 3, 719-739
B. Ebeling and P. Vana
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‘On the Mechanism of Ring-Expansion Polymerization of Thiiranes’. Macromolecular Chemistry and Physics, 2011, 212, 1263-1275
J.-H. Schuetz and P. Vana
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‘Insights into the Ring-Expansion Polymerization of Thiiranes with 2,4-Thiazolidinedione’. Macromolecular Chemistry and Physics 2013, 214, 1484-1495
J.-H. Schuetz, L. Sandbrink, P. Vana
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‘Titin-Mimicking Polycyclic Polymers with Shape Regeneration and Healing Properties’. Polymer Chemistry 2015 (Journal Cover Article)
J.-H. Schuetz, W. Peng, and P. Vana
