Verdazyl radicals as mediators in living radical polymerisation and dopamine end-functionalised polymers for application as friction modifiers

摘要

Verdazyl Radicals as Mediators in Living Radical Polymerisation: The aim of this work was to investigate verdazyl radicals as an alternative to nitroxides as mediators in stable free radical polymerisation. Verdazyl radicals and their unimolecular initiators were synthesised and utilised in the polymerisation of styrene and n-butyl acrylate. Varying degrees of success was observed in the polymerisations depending on the structure of the verdazyl radical. The polymerisation of methyl methacrylate and the copolymerisation of styrene and methyl methacrylate were also investigated. Correlations between observed molecular weight and theoretical molecular weight were poor but may be improved by optimisation of the reaction conditions. Electron paramagnetic resonance was used to elucidate the radical structure as well as to confirm the living nature of the polymerisation technique. Electron paramagnetic resonance was also utilised to provide an insight into radical stability and reactivity in the various reactions undertaken. Dopamine End-Functionalised Polymers for Application as Friction Modifiers: The aim of this work was to synthesise oil soluble dopamine end-functionalised polymers for mechanical testing to determine if the polymers can reduce friction by film formation at a surface. A dopamine based initiator was synthesised and used in Cu(I) and Cu(0) mediated polymerisations with little success and the dopamine catecholic end-group could not be identified as the polymer end-group. To enable a successful living polymerisation, the catechol groups on dopamine required protection. Complete deprotection of the catechol group can be achieved post polymerisation. The polymerisation of lauryl methacrylate was achieved using a polymerisation method designed for the long chain, non-polar molecule which utilised Cu(I)Cl. The polymerisations were scaled up to obtain a baseline, protected dopamine and deprotected dopamine polymers for mechanical testing. A reduction in friction and wear observed for the deprotected dopamine polymer, however, corrosion was also observed and may have affected the results.