Copolymerisation of cyclic esters by yttrium initiators for increasingly sustainable applications

Catchpole, Pip and Platel, Rachel (2023) Copolymerisation of cyclic esters by yttrium initiators for increasingly sustainable applications. PhD thesis, Lancaster University.

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Abstract

In chapter 1, the use and dependence on single-use plastics is explored using big picture thinking. Single-use coffee cups are used as a case study, and their invention and acceptance into society is discussed. Issues with the polyethylene plastic used to line paper to make these cups are explored, and potential alternatives are evaluated. Chapter 2 focuses on polymers and their properties. Methods used to alter polymer properties and how polymer microstructure influences these properties are discussed. Poly(3-hydroxybutyrate) is introduced as a potentially renewable polymer that could replace some polyolefins in current applications. The formation of poly(3-hydroxybutyrate) from β-butyrolactone by ring-opening polymerisation facilitated by metal catalysts is described. In chapter 3, the yttrium complexes that are used as catalysts for ring-opening polymerisation throughout chapters 4 and 5 are introduced and their synthesis is described. The complexes are all characterised by 1H and 13C NMR spectroscopy and, in some cases, solid-state structures of the complexes were obtained. In chapter 4, β-butyrolactone and γ-butyrolactone are polymerised and copolymerised. Various reaction conditions are explored to determine their influence on polymer microstructure and properties. In particular, the molecular weights, compositions, and thermal properties of the polymers are explored. In this work, incorporation of 87% γ-butyrolactone into poly(3-hydroxybutyrate) was achieved, which was the highest reported at the time of writing. In chapter 5, β-butyrolactone and ε-decalactone are polymerised and copolymerised, and characterised in a similar manner to the polymers produced in chapter 4. Monomer sequences were determined for a selection of copolymers, which suggested block copolymers could be synthesised in a one-pot synthesis under the reaction conditions used. In chapter 6, the conclusions and outlook from the findings in chapters 3-5 are discussed. Chapter 7 contains the experimental details.