Controlled radical polymerization (CRP) is a very robust and powerful technique that allows preparing well-defined functional architectures from a wide range of monomers. Among the numerous chemistries employed in macromolecular engineering, thiol chemistry currently stands as one of the most versatile tool for synthesis of functional polymers and materials. However, thiol groups are not compatible with controlled radical polymerization processes since they induce irreversible chain transfer. A simple methodology to prepare well-defined polythiol copolymers by controlled radical polymerization was developed to address this issue.Use of xanthate, dithiocarbamate and thioacetate moieties as thiol protecting groups was investigated. Model reactions were conducted to study the effect of these protecting groups during controlled radical polymerization of acrylates, methacrylates and styrenics. Deprotection of these moieties by aminolysis was also investigated.A simple two steps procedure allowed preparing monomers carrying S-alkyl-O-ethyl xanthate moiety as thiol protecting group. Polythiols were obtained by copolymerizing the functional monomers with (meth)acrylates and subsequent aminolysis of the protecting groups. Both atom transfer radical polymerization (ATRP) and reversible addition-fragmentation chain transfer (RAFT) polymerization were successfully employed to prepare well-defined polythiols. Functionalization of polythiol copolymers was achieved via thiol-ene addition, Michael addition and thiol-disulfide exchange. Thiol deprotection and functionalization were conducted in one-pot for Michael addition and thiol-disulfide exchange. A complete conversion of thiol groups was observed for all three types of reactions, exemplifying the potential of polythiols for the preparation of functional materials.

Thiocarbonyl and thioester moieties as thiol protecting groups for controlled radical polymerization

246th National Meeting (2013)

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