| Резюме: | <p>This thesis describes the development of homogeneous catalysts for epoxide/carbon dioxide (CO2) ring-opening copolymerisation (ROCOP). The objective is to increase understanding of the polymerisation mechanism and factors controlling catalyst performance. It ends with an application of the best catalyst to polymerisation of epoxide, carbon dioxide and lactide using ‘switch’ catalysis.</p>
<p><strong>Chapter 1</strong> provides an introduction to the ROCOP of epoxides and CO2, with a particular focus on catalyst development and mechanism. It also introduces the concept of ‘switchable’ catalysis.</p>
<p><strong>Chapter 2</strong> details the mechanistic exploration of a high performance heterodinuclear Co(III)K(I) catalyst for propylene oxide/carbon dioxide (CO2) ring-opening copolymerisation (ROCOP). A detailed computational investigation of the full catalytic cycle is performed and barriers match with experimental ones. The proposed mechanism occurs with a rate determining step involving epoxide activation at Co(III) and nucleophilic attack by a carbonate bound to the K(I). Further examination, both experimentally and computationally, of the cyclic carbonate formation is undertaken and showed that it occurs via both a random chain scission and chain ‘unzipping’ mechanism.</p>
<p><strong>Chapter 3</strong> details a structure-activity study of the Co(III)K(I) catalyst system underpinned by the findings in Chapter 2. The investigation explores the effect of ligand structure on the Co(III/II) redox potential, activity and selectivity in propene oxide (PO)/carbon dioxide (CO2) ring-opening copolymerisation (ROCOP). It rationalises the effects of these changes using the polymerisation mechanism. The key finding is that a lower redox potential, corresponding to higher electron density at Co(III), leads to higher activity and selectivity in propylene oxide (PO)/carbon dioxide (CO2) ringopening copolymerisation (ROCOP).</p>
<p><strong>Chapter 4</strong> details the application of a high activity and selectivity Co(III)K(I) catalyst to the ‘switchable’ catalysis of ally glycidyl ether (AGE)/CO2 and L-lactide (L-LA), producing a block polymer (PLLA-b-PAGEC-b-PLLA). The experimental method, involving a new gas line, is developed and the characterisation proofs of ‘switch’ are presented.</p>
<p><strong>Chapter 5</strong> outlines the key developments of this thesis and suggests potential future directions for the research.</p>
<p><strong>Chapter 6</strong> provides experimental details for Chapter 2-4.</p>
<p><strong>Chapter 7</strong> is an appendix that provides supplementary information, figures and data that support the work and discussion through Chapter 2-4.</p>
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