Design and application of novel biodegradable chain extenders and surface-tuneable hyperbranched chain terminating agents in thermoplastic polyurethane elastomers

• Main Author: Roberts, Zoe J.
• Published: University of Warwick 2017
• Subjects: 540; QD Chemistry
• Online Access: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.752483

This thesis is in two distinct sections. In the first section, novel diketopiperazines are synthesised and incorporated as chain extenders into thermoplastic polyurethane elastomers and the resulting mechanical, thermal and degradative properties are analysed. In the second section, hyperbranched chain terminating agents are synthesised from 1,1’-carbonyldiimidazole in a one-pot process and the potential applications of fluorinated hyperbranched chain terminating agents are investigated. Chapter 1 has three parts. First, the synthesis and applications of polyurethanes are introduced and the current market trends and growth projections are discussed. Secondly, an overview of current literature covering biodegradable polymers focusing on the incorporation of amino acids into polyurethanes and their potential applications is presented. Thirdly, hyperbranched polymers are introduced and a focus is made on the synthesis of isocyanate and non-isocyanate polyurethanes and polyureas. In chapter 2, the use of the dipeptides of tyrosine and glutamic acid as chain extenders in polyurethane synthesis is explored. The dipeptide of glutamic acid is modified to incorporate a higher content of ester and amide degradable linkages with aromatic character that form comparable chain extenders to tyrosine dipeptide. Their use in the organocatalysed step-growth polymerisation of novel thermoplastic polyurethane elastomers is described. In chapter 3, the resulting tyrosine and glutamic acid-derived thermoplastic polyurethane elastomers are utilised to explore the variation of thermal, mechanical and degradative properties of a range of polymer compositions. In chapter 4, the synthesis of novel hyperbranched materials polymerised in a one-pot, temperature-controlled sequential synthesis incorporating aromatic or fluorinated functional chain ends from both carbonylbiscaprolactam and 1,1’-carbonyldiimidazole precursors is described. In chapter 5, 1,1’-carbonyldiimidazole derived hyperbranched polymers are incorporated into an existing thermoplastic polyurethane formulation and the surface properties are studied by varying polymer composition. In chapter 6, the significant findings and conclusions are summarised. In chapter 7, the experimental methods used are set out.