Design of crystallisation-inhibited polymer networks for absorption and storage of high mechanical impacts

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Spiders use draglines as safety-lines in the event of a fall as well as for catching fast flying insects. Such draglines are capable of absorbing and dissipating tremendous amounts of kinetic energy. So far there is no synthetic material that matches these mechanical characteristics of spider dragline silk.The goal of this project is the design of a synthetic material that is capable of mimicking the mechanical properties of spider draglines with regard to its kinetic energy absorption. We propose that this is achievable by a material that transforms itself from an amorphous, rubber-like into a highly crystalline, high-modulus state upon stretching to large elongations and retains the latter after removing the stretching force. To avoid misunderstandings: This proposal is not about spider silk but deals with a synthetic material with high kinetic energy absorption capability. Cold-programmable shape memory polymers (SMPs) are promising candidates to meet the corresponding requirements. Thus we will focus on the preparation, characterization and optimization of novel crystallization-inhibited polymer networks that stay amorphous at room temperature and crystallize strain-induced upon deformation. First satisfactory results could be acquired from preliminary works on shape memory natural rubber (SMNR) and shape memory polyethylene (SMPE). In this project, SMPs based on natural rubber will be optimized and novel networks based on polymers like syndiotactic polypropylene (sPP) and polyisobutylene (PIB) will be prepared that allow large strains, large crystallinity, and crystallization-rates in order to maximize the energy absorption capacity and minimize the elastic rebound.