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Title: Polymerisation catalysts to make polyesters and copolymers
Author: Yuntawattana, Nattawut
ISNI:       0000 0004 9355 380X
Awarding Body: University of Oxford
Current Institution: University of Oxford
Date of Award: 2020
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The world needs more sustainable polymers and although there are some promising frontrunners, the range of degradable and renewably sourced plastics remains narrow. One issue to address is to improve the efficiency of production of aliphatic polyesters and to expand the range and properties of easily accessible degradable materials. This thesis describes new In(III), Sn(II), Ti(IV), and Zr(IV) polymerisation catalysts used to make aliphatic polyesters and copolymers. The overall objective is to develop efficient catalysis to improve upon the structures, scope and range of degradable polyesters. This is achieved by stereoselective lactide ring-opening polymerisation, by epoxide/anhydride ring-opening copolymerisation and by switch catalysis using mixtures of lactide/lactone, epoxide and anhydride. Chapter 3 presents a series of phosphasalen In(III) complexes, with different diamine linkers and phosphorous substituents, which are highly active and iso-selective in the ring-opening polymerisation of racemic lactide. The highest performing catalyst produces isotactic polylactide (up to 92 %), via a chain-end control mechanism. Additionally, the complexes polymerise a range of other lactones with the activity depending strongly on both the catalyst and lactone structures. Chapter 4 describes a series of phosphasalen Ti(IV) and Zr(IV) complexes which are active and, in some cases, highly selective for epoxide and anhydride ring-opening copolymerisations without any co-catalyst. Phosphasalen complexes show superior activity and selectivity over their salen and salalen analogues, highlighting the importance of the iminophosphorane backbone. A polymerisation mechanism is proposed, based on kinetic experiments and the polymerisation propagating intermediate isolation. Chapter 5 describes the first report of an industrially relevant catalyst, Sn(OMe)₂, for both epoxide/anhydride ring-opening copolymerisation and ‘Switch’ catalysis using lactone, epoxide and anhydride mixtures. The switch catalysis yields new polyester-ethers with microstructures including block-, tapered-, and gradient-copolymers. Selected copolymers are efficient toughening additives, at just 2 wt. % loading, for polylactide increasing toughness values by 400%.
Supervisor: Williams, Charlotte Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available