Abstract
The persistence of petrochemical-based polymers within our environment has pushed the need for more sustainable, biodegradable polymer production. Several compostable aliphatic polyesters can be produced via the metal-catalysed ring-opening polymerisation (ROP) of cyclic esters, with poly(lactide) being the most commercially successful polymer. Due to its use with the biomedical and food-based applications, it is desirable to produced catalysts which are highly active, benign, and cost effective. Currently, research is focussed upon stereoselective ROP catalysts or improving catalysts biocompatibility through use of benign metals or metal-free catalysts. However, limited attention has been paid to heterogeneous catalysts, where easy purification, and recovery and reuse can be carried out, leading to a reduction in production costs. Moreover, the application of these catalysts into a heterogeneous flow reactor can help facilitate in future scale-up.Chapter 3 explores polystyrene-immobilized zinc complexes based on a tridentate N,N,O-bisaminophenolate ligand, known for producing highly active zinc complexes. The effect of ligand substituents and carboxylate initiating ligands was investigated to determine if the benefits of a tridentate ligand system translated to a heterogeneous complex.
Chapters 4 and 5 investigate alternative support types for heterogeneous ROP in both batch and flow conditions. Solid-phase organic synthesis emphasizes tailoring support types to reactions, considering surface interactions, swelling, and porosity. In heterogeneous lactone ROP, only a few support types, primarily silica and polystyrene, have been explored. This chapter examines the suitability of alternative supports, including TentaGel and HypoGel for their semi-heterogeneous nature, and polyHIPE for its high surface area and well-defined porosities.
Chapter 6 explores the chemical recycling of poly(lactide). For industrial relevance, chemical recycling of commercial polymers must be scalable and enable easy monomer recovery. Flow chemistry's benefits were utilized to achieve a closed system without specialized batch equipment, allowing the exploration of lower boiling point solvents for polymer depolymerization.
| Date of Award | 19 Feb 2025 |
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| Original language | English |
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| Supervisor | Antoine Buchard (Supervisor) & Tanja Junkers (Supervisor) |