Design and Synthesis of Bio-Inspired Functional Adhesive Polymer Coatings

Abstract

Inspired by the remarkable adhesive properties of mussels, the versatile chemistry of the catechol functional group is increasingly being utilised in a wide range of fields. In the work described in this thesis, copolymers were synthesised using the catechol-containing functional monomer dopamine methacrylamide (DMA) and its acetonide-protected analogue (ADMA) with the aim of producing a functional surface coating capable of immobilising biomolecules. The reactivity ratios for the free radical copolymerisation of ADMA with methyl methacrylate (MMA) or glycidyl methacrylate (GMA) were found to be rMMA = 2.21 ± 0.26 and rADMA = 0.17 ± 0.03, and for the GMA/ADMA copolymerisation rGMA = 1.96 ± 0.49 and rADMA = 0.18 ± 0.08. Accordingly, significant compositional drift was observed in polymerisations allowed to proceed to full conversion. Reversible addition-fragmentation chain-transfer (RAFT) polymerisation of ADMA with methacrylate comonomers was used to synthesise functional diblock copolymers and statistical copolymers with a gradient structure. Co- and terpolymers synthesised using hydroxyethyl methacrylate (HEMA), GMA and DMA were deposited onto silicon wafers by spin coating. Use of DMF as the spin-coating solvent enabled the deposition of homogenous films. Polymer films were also deposited directly from solution using immersion coating from a solution of dimethylformamide (DMF) containing 1% pyridine, taking advantage of the adhesive catechol functional group. The spin coated films were analysed by in-situ ellipsometry, captive bubble contact angle analysis and electrokinetic measurements. It was demonstrated that DMA had a large impact on chain mobility at the surface, ascribed to strong intermolecular H-bonding, however, the degree of swelling was largely influenced by the GMA content in the copolymers, ascribed to ring-opening induced crosslinking. Finally, it was demonstrated, using in-situ ellipsometry and quartz crystal microbalance, that a monolayer of IgG antibody was immobilised on a spin-coated copolymer film via covalent reaction with epoxide side chains.