Catalysts for the production of sustainable biopolymers

The development of biodegradable plastics from sustainable sources is at the forefront of chemical research. One such example is the production of polylactide (PLA) via the ring-opening polymerisation (ROP) of the cyclic ester lactide (LA). Current industrial metal initiators utilised for the ROP of LA do not allow control over the stereochemistry of the resulting product. This thesis will investigate various initiators containing a variety of ligand sets for the ROP of rac-LA. Chapter 1 introduces the ROP of rac-LA, the mechanisms utilised and the methods employed for characterisation of PLA. A review of the current literature of recent developments in the production of PLA via various metal initiators is also included. Chapter 2 reports the development of a series of group (IV) complexes containing various amine tris(phenolate) ligands, where the sterics and electronics have been varied. Such complexes were trialled for the ROP of rac-LA as well as the ROP of trimethylene carbonate (TMC). The ability of such initiators to produce copolymers of rac-LAlTMC and rac-LAlisosorbide was also investigated and discussed. Chapter 3 describes the synthesis of a range of group (IV) complexes containing Salalen ligands. The sterics of the ligands have been varied and the ability of the initiators to initiate the ROP of rac-LA in a stereocontrolled fashion has been investigated. Furthermore, the complexes have been trialled for the degradation of PLA into methyl lactate, an important starting material in the production of LA. Chapter 4 investigates the development of AI(III) Salalen complexes for the ROP of rac-LA, where the sterics and electronics of the ligand have been varied. Kinetic investigations have been carried out to aid the understanding of the polymerisation process. Chapter 5 provides details of the reaction procedures for the synthesis of ligands, complexes and polymers. Kinetic procedures are also reported together with details of the analytical techniques employed.EThOS - Electronic Theses Online ServiceGBUnited Kingdo