Polymerization of Zwitterionic Sulphobetaine Methacrylate and Modification of Contact Lens Substrate

Abstract: In this study, the zwitterionic monomer [2-(methacryloyloxy)ethyl] dimethyl-(3-sulfopropyl) ammonium hydroxide (SBMA) was polymerized in a controlled manner by reversible addition-fragmentation chain transfer (RAFT) polymerization. The SBMA was also polymerized by atom transfer radical polymerization (ATRP) but in a less controlled manner why ATRP was discarded for further use in the study. The RAFT polymerized p(SBMA) was end-group modified through aminolysis forming a thiol end-group. The zwitterionic polymers have considerable anti-fouling properties and could be of use in contact lenses to prolong the wear-time. Model contact lens hydrogel substrates were synthesized, through free radical polymerization, consisting of 1/3 of silicone monomer, 2/3 of dimethyl acrylamide (DMA) and small percentages of glycidyl methacrylate (GMA) and ethylene glycol dimethacrylate (EGDMA) cross-linker. These had poor mechanical strength and could only be used to explore the effect of surface chemical modification. The p(SBMA)-thiol was ‘graftedto’, by applying thiol-epoxide ring-opening, at a free radical polymerized co-polymer consisting of DMA and GMA indicating that this could work for the model hydrogel surfaces.