Thesis
Fast, selective and tolerant polymerisation catalysts for the synthesis of low molecular weight polyester and polycarbonate polyols
- Abstract:
-
This thesis describes the development of novel Al(III)/K(I) heterodinuclear catalysts for use in the synthesis of low molecular weight polyesters and polycarbonates by the ring-opening copolymerisation (ROCOP) of epoxides/anhydrides and epoxides/carbon dioxide (CO2), respectively.
Chapter 1 introduces these two ROCOP reactions outlining their mechanisms and catalyst development. The use of protic compounds as chain transfer agents (CTA) to control the polymer molecular weight and the challenges associated with designing catalysts stable to high CTA loading is discussed.
Chapter 2 presents a series of Al(III)/K(I) catalysts, assessing the impact of modifications to the ancillary ligand on the ROCOP of cyclohexene oxide (CHO) with phthalic anhydride (PA). Catalysts are compared by rate constants, turn over frequencies (TOF), and polyester selectivity. The lead catalyst is then tested for CTA loading tolerance, revealing an increase in activity with increased alcohol (CTA) loading achieving optimal rate at 200 equiv. CTA with TOF = 1890 h-1. This represents a 4.4x increase in rate over the reaction without CTA, a remarkable result for epoxide/anhydride ROCOP.
Chapter 3 explores the same catalyst series, as in Chapter 2, but for CHO/CO2 ROCOP. The same parameters are compared between the catalysts, suggesting a different lead catalyst, with a promising rate compared with other literature Al(III)-based polycarbonate ROCOP catalysts. Through kinetic experimentation the polymerisation rate law is established and an equilibrium for CO2 insertion is revealed and then quantified.
Chapter 4 investigates further the rate law and kinetic influence of CTA on the Al(III)/K(I) catalysed ROCOP. A first order rate dependence on each of: catalyst, epoxide and CTA is deduced from kinetic experimentation. Subsequent CTA scope, kinetic isotope effect reactions and tests on CTA binding to the catalyst imply that the rate enhancement occurs from coordination of alcohol end-capped chain ends to the K(I) which labilises the propagating nucleophile (carboxylate).
Chapter 5 summarises the main findings of this thesis and its implications. An outlook section suggests directions for future research that can build upon the work presented here.
Chapter 6 provides experimental details for Chapters 2-4.
An Appendix is included, presenting all the supplementary figures and data that complement the discussion throughout Chapters 2-4.
Actions
Access Document
- Files:
-
-
(Preview, Dissemination version, pdf, 19.2MB, Terms of use)
-
Authors
Contributors
- Institution:
- University of Oxford
- Division:
- MPLS
- Department:
- Chemistry
- Role:
- Supervisor
- Funder identifier:
- https://ror.org/0439y7842
- Funding agency for:
- Shellard, EJK
- Grant:
- EP/V038117/1
- Programme:
- Prosperity Partnership (Title: Cleaner Futures (Next-Generation Sustainable Materials for Consumer Products))
- DOI:
- Type of award:
- DPhil
- Level of award:
- Doctoral
- Awarding institution:
- University of Oxford
- Language:
-
English
- Keywords:
- Subjects:
- Deposit date:
-
2025-08-06
- ARK identifier:
Terms of use
- Copyright holder:
- Edward JK Shellard
- Copyright date:
- 2025
If you are the owner of this record, you can report an update to it here: Report update to this record