Novel synthesis of block copolymers via the RAFT process

[摘要] The synthesis of complex architectures, namely block copolymers with tailored enduseproperties, is currently an important research area in academia and industry. Thechallenge is finding a versatile polymerization technique capable of controlling themolecular properties of the formed copolymers, which in turn determines theirmacroscopic properties. Reversible addition-fragmentation chain transfer (RAFT)-mediated living polymerization is a robust technique capable of producing controlledpolymer products. With the great advances in living polymerization techniques andthe environmental awareness of society there is an increasing demand to producethese polymer products via the RAFT living technique in heterogeneous media.Conventional emulsion and miniemulsion polymerization present various problemswhen used to produce polymers mediated by the RAFT process. There is an inherentneed to find cost effective and flexible operating conditions to conduct RAFTpolymerization in heterogeneous media with the ability to produce well-defined blockcopolymers.In this study the use of three novel trithiocarbonate RAFT agents to produce welldefinedAB-type, ABA-type and star block copolymers via the RAFT process wasinvestigated. Optimal operating conditions for the production of living blockcopolymers in homogenous and heterogeneous media were determined. The mainfocus was on the development of the RAFT process in heterogeneous media toefficiently produce block copolymer latex products. The RAFT-mediatedminiemulsion polymerization system stabilized with non-ionic surfactants wasthoroughly investigated. The ability of the ab initio and in situ RAFT-mediatedemulsion polymerization systems to produce controlled latexes was demonstrated.Controlled block copolymer products were successfully synthesized in homogenousand heterogeneous media via the RAFT process when the optimum reactionconditions were chosen.

[发布机构] Stellenbosch University