Well-defined polymethacrylates: the effect of molar mass, chemistry, and composition on thermoresponsive properties
File(s)
Author(s)
Wang, Lezhi
Type
Thesis
Abstract
This PhD thesis investigates thermoresponsive polymethacrylates through three distinct but interconnected studies, focusing on polymer parameters to enhance understanding and control of their thermoresponsive behaviours. The first study examines the impact of molar mass on the thermoresponsive properties of 28 bipolymers. Polymers were synthesised using 2-(dimethylamino)ethyl methacrylate (DMAEMA), oligo(ethylene glycol) methyl ether methacrylate (OEGMA, average Mn = 300 g/mol), and methyl methacrylate (MMA) in both diblock and statistical architectures (DMAEMA-b-MMA, DMAEMA-co-MMA, OEGMA-b-MMA, and OEGMA-co-MMA). By varying the molar mass from 3,000 to 43,000 g/mol, this study examines how it affects thermoresponsive behaviour, highlighting trends in cloud point temperatures across polymer series and configurations. The second study introduces the ionic comonomer N-(2-methacryloyloxyethyl)pyrrolidone (NMEP) into DMAEMA-MMA to create terpolymers in triblock and statistical forms. Using group transfer polymerisation (GTP) and reversible addition-fragmentation chain transfer (RAFT) polymerisation, polymer architectures (ABC, BAC, BCA, and statistical) were varied at a target molar mass of approximately 12,000 g/mol to investigate how comonomer arrangements influence thermoresponsive properties and self-assembly behaviour. The final study investigates novel terpolymers based on the OEGMA family, featuring a hydrophobic block of ethylene glycol methyl ether methacrylate (MEGMA) and two thermoresponsive components: OEGMA and di(ethylene glycol) methyl ether methacrylate (DEGMA). Designed with a fixed ABC architecture (OEGMA-b-MEGMA-b-DEGMA) and a molar mass of 8100 g/mol, 16 copolymer compositions were synthesised by varying the hydrophobic MEGMA content from 25% to 55% w/w. Binary blends of the triblock terpolymer with its diblock analogue (OEGMA-b-MEGMA) were studied to optimise thermogelation windows at physiological temperatures, aiding further investigations into drug release profiles. Overall, these studies explore the synthesis and characterisation of thermoresponsive polymethacrylates, focusing on molar mass, architecture and chemistry, and composition in Chapters 4, 5, and 6, respectively. These findings reveal how these parameters influence thermoresponsive behaviours, supporting rational design and future applications.
Version
Open Access
Date Issued
2024-08-19
Date Awarded
01/01/2025
License URL
Advisor
Georgiou, Theonitsa
Publisher Department
Materials
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)