Dibromomaleimide End Functional Polymers by RAFT Polymerization Without the Need of Protecting Groups

Polymers bearing the dibromomaleimide (DBM) group as a functional chain end have been synthesized by RAFT polymerization. A DBM functional chain transfer agent (CTA) was utilized to afford well-defined PtBA, PMA, and PTEGA, without the requirement of protecting group chemistry. It was found that RAFT polymerization of NIPAM and styrene with this CTA was severely retarded/inhibited which is ascribed to their relatively low propagation rate constants compared to acrylates. This observation is accounted for by a reversible trapping of propagating radicals by the DBM group in RAFT polymerizations using a monomer with low kp. However, further attempts to synthesize DBM-terminated PtBA and PMA by ATRP using an analogous initiator were unsuccessful, and broad PDI were observed. Furthermore, highly efficient postpolymerization functionalization of DBM-terminated PMA produced by RAFT, with the model compound thiophenol was also demonstrated.