Catalyst and monomer design : targeting polymer properties via organic catalysed ring opening polymerisation

The work undertaken in this thesis focuses on the synthesis of biodegradable materials with desirable properties via the organic catalysed ring opening polymerisation (ROP) of cyclic monomers. Influence over the resulting polymer properties is obtained either through the careful design of catalyst or monomer. Chapter 1 reviews organic catalysts that have been developed for ring opening polymerisation, focussing on particular advantages and disadvantages of each and providing an overview of compatible types of cyclic monomers. (-)-Sparteine in conjunction with a co-catalyst is capable of synthesising isotactic PLA with very few stereoerrors, but its sudden commercial unavailability has led to a need for a replacement. Chapter 2 therefore focuses on the synthesis of benzyl bispidine, a (-)-sparteine analogue, demonstrating its almost identical behaviour as a ring opening polymerisation catalyst to produce polymers with optimal properties from lactide. Post-polymerisation provides access to functionalities not compatible with ROP, and allowing careful tailoring of polymer properties. Whilst a range of cyclic carbonate monomers have been designed to provide this ability after ROP, poly(carbonate)s with only low glass transition have been obtained. Chapter 3 describes the synthesis of 9-vinyl-2,4,8,10-tetraoxaspiro[5.5]undecan-3-one (VDC), a sterically bulky, vinyl functional cyclic carbonate and its subsequent ROP and thiol-ene functionalisation to yield functional poly(carbonate)s with improved thermal properties. In Chapter 4, work is undertaken to tailor the glass transition temperature of functional poly(carbonate)s. Copolymers of VDC with the allyl functional cyclic carbonate allyl 5-methyl-2-oxo-1,3-dioxane-5-carboxylate (MAC) are synthesised to demonstrate the ability to produce poly(carbonate)s with a predetermined glass transition temperature after post-polymerisation functionalisation depending on the initial monomer feed ratio. In Chapter 5 the results from the previous chapters are discussed, with the experimental data obtained for these chapters provided in Chapter 6