Evaluation of thiocarbonyl and thioester moieties as thiol protecting groups for controlled radical polymerization

Abstract

Thiol chemistry is a versatile and powerful tool for the preparation of functional polymers and materials. In that regard, xanthate, dithiocarbamate and thioacetate moieties were evaluated as thiol protecting groups for radical polymerization. Model reactions were conducted to study the effect of these moieties during RAFT polymerization of (meth)acrylates and styrene. The removal of these protecting groups by aminolysis was also investigated. The S-alkyl-O-ethyl dithiocarbonate moiety proved to be the best all-around protecting group since it did not induce any side reaction during controlled radical polymerization of all three types of monomers and could be easily and completely removed at room temperature. Monomers carrying a xanthate group were synthesized and used to prepare various (protected) polythiols with (meth)acrylate backbones by RAFT polymerization or ATRP. One-pot thiol deprotection and functionalization was carried out to exemplify the simplicity and efficiency of the present approach for the preparation of functional polymers and materials.