Synthesis and self-assembly of linear and cyclic degradable graft copolymers

This thesis explores the use of ring-opening polymerisation (ROP) and reversible addition-fragmentation chain transfer (RAFT) polymerisation to prepare linear and cyclic graft copolymers with a polycarbonate backbone. The solution properties and self-assembly behaviour of these linear and cyclic graft copolymers with hydrophilic side arms is also described. Chapter 1 introduces the polymerisation techniques used in this thesis, namely ROP and RAFT, and provides a review of the self-assembly of polymers that possess a cyclic topology. In Chapter 2, the synthesis and ROP of a novel cyclic carbonate monomer bearing pendent norbornene functionality is described. Successful postpolymerisation modification of the norbornene functionality is demonstrated for a range of addition reactions; 1,3-dipolar cycloaddition, inverse electron demand Diels-Alder reaction and radical thiol-ene addition, and is also shown to provide access to multi-functional polycarbonates. Attempts to prepare graft copolymers via the grafting of thiol-terminated polymer chains to the norbornene-functional polycarbonate backbone are also described. Chapter 3 describes the optimised synthesis of linear graft copolymers via the ROP of a RAFT chain transfer agent (CTA)-functional cyclic carbonate monomer and subsequent RAFT polymerisation to grow polymer chains from the RAFT CTA sites located along the resulting polycarbonate backbone. This methodology was used to prepare a polycarbonate-g-poly(Nisopropylacrylamide) amphiphilic copolymer and its self-assembly to afford degradable, thermoresponsive particles is demonstrated. In Chapter 4, the optimised procedures developed in Chapter 3 for the preparation of linear graft copolymers are applied to the preparation of welldefined cyclic graft copolymers with a degradable cyclic polycarbonate backbone and a range of side arm compositions. Chapter 5 investigates the solution properties and self-assembly behaviour of linear and cyclic graft copolymers with hydrophilic poly(N-acryloylmorpholine) side arms and a hydrophobic polycarbonate backbone, prepared using the methodologies developed in Chapters 3 and 4. Chapter 6 provides a summary of the key findings of Chapters 2 – 5 and Chapter 7 provides the experimental methods of this thesis