Synthesis and applications of functional graft copolymers

This thesis investigates new synthetic methods for preparing graft copolymers using reversible addition-fragmentation chain transfer (RAFT) polymerisation, their solution self-assembly, and use as friction modifier additives in oil. In the first study two new synthetic routes are described, which make use of the dynamic addition and fragmentation of grafts to and from the backbone in the previously reported Z group approach polymerisation mechanism. The first synthetic route involves an interchange of grafts between distinct graft copolymer starting materials, yielding a product with a mixed graft distribution. In the second method linear chains are transferred to a RAFT agent-decorated polymer, giving a graft copolymer product. The unique RAFT process provides a convenient means to prepare heterograft copolymers and extensive graft copolymer libraries by simply adjusting the stoichiometry of each reaction. The second study investigates the polymerisation-induced self-assembly of sparsely grafted polymers during reactions in which grafts are polymerised in a backbone-selective solvent. The phase separation of grafts is shown to result in the formation of clustered particles and various multicore morphologies due to the ability of the branched architecture to freeze chain entanglements and bridge separate core domains. The graft copolymer architecture offers a straightforward route to less commonly encountered morphologies and gives additional handles for controlling the polymer structure and the properties of the obtained materials. In the third study, various oil-soluble graft copolymers with a surface active polar segment are assessed for use as friction modifier oil additives. The incorporation of a polar segment into the polymer structure is shown to promote mass deposition onto steel, ideal for forming lubricating boundary films. Macrotribological tests indicate a significant friction reduction efficacy for all tested polymers but no clear distinction between the different architectures