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Title: Synthesis and post-polymerisation modification of degradable polymers based on polycarbonates/polyesters prepared using ring-opening copolymerisation
Author: Yi, Ni
ISNI:       0000 0004 7430 6555
Awarding Body: University of Oxford
Current Institution: University of Oxford
Date of Award: 2018
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This thesis describes the synthesis of degradable materials based on functional aliphatic polycarbonates/polyesters synthesised via ring-opening copolymerisation (ROCOP) and post-polymerisation modifications. Chapter 3 details the synthesis of cationic poly(ester-b-carbonate-b-ester) via ringopening copolymerisation of CO2 and vinyl-cyclohexene oxide (v-CHO), ringopening polymerisation (ROP) of rac-lactide, and subsequent post-polymerisation modifications of this material through a radical thiol-ene reaction and a quaternisation reaction. These cationic polymers show high surface zeta-potential (> 40 mV) and display effective antibacterial properties with killing efficiencies of > 99.9% against Gram-negative bacteria Escherichia coli. Chapter 4 describes the synthesis of amphiphilic block poly(phosphoester-b-carbonate-b-phosphoester)s using ROCOP of CO2 and v-CHO and ROP of ethyl ethylene phosphate (EP). These amphiphilic block polymers self-assemble into either micelles or vesicles, depending on the hydrophobic/hydrophilic block ratio. The potential use of the vesicles in drug delivery is also described, and initial results detailing the enzymatic degradation of these vesicles are presented. In addition, the hydroboration-oxidation is investigated as a new post-polymerisation modification method to functionalise an alkene-containing polycarbonate, poly(vinylcyclohexene carbonate) (VPC). The hydroxyl functionalised polycarbonate shows improved hydrophilicity and cell adhesion, compared to the unfunctionalised precursor. The side chain hydroxyl groups are then tested for making graft poly(carbonate-g-phosphoester). Chapter 5 further investigates the use of the hydroboration-oxidation reaction in functionalising poly(cyclohexadiene carbonate) (CPC) and poly(vinylcyclohexenemaleate) (V,MPE). A selective post-polymerisation modification is also demonstrated on a blend of CPC and VPC or V,MPE featuring both terminal and internal alkene groups using the hydroboration-oxidation method, where the terminal alkene groups are functionalised exclusively. Lastly, an orthogonal post-polymerisation approach is carried out on the unreacted internal alkene groups of hydroxyl-containing V,MPE via thiol-ene reactions to install other functional groups such as carboxyl, amine and methoxy-poly(ethylene glycol).
Supervisor: Williams, Charlotte K. Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Chemistry ; post-polymerisation modification