A Strategy for Controlling the Polymerizations of Thiyl Radical Propagation by RAFT Agents

A new strategy that could enable the polymerizations of thiyl radical propagation to be controlled by existing RDRP methods has been reported. The key to this strategy is the propagating thiyl radicals could undergo desulfurization with isocyanides to generate stabilized alkyl radicals, thereby allowing for controlling the polymerization via RAFT agents, leading to the formation of main-chain polymers with well-defined architectures.

Abstract

The ability to extend the polymerizations of thiyl radical propagation to be regulated by existing controlled methods would be highly desirable, yet remained very challenging to achieve because the thiyl radicals still cannot be reversibly controlled by these methods. In this article, we reported a novel strategy that could enable the radical ring-opening polymerization of macrocyclic allylic sulfides, wherein propagating specie is thiyl radical, to be controlled by reversible addition–fragmentation chain transfer (RAFT) agents. The key to the success of this strategy is the propagating thiyl radical can undergo desulfurization with isocyanide and generate a stabilized alkyl radical for reversible control. Systematic optimization of the reaction conditions allowed good control over the polymerization, leading to the formation of polymers with well-defined architectures, exemplified by the radical block copolymerization of macrocyclic allylic sulfides and vinyl monomers and the incorporation of sequence-defined segments into the polymer backbone. This work represents a significant step toward directly enabling the polymerizations of heteroatom-centered radical propagation to be regulated by existing reversible-deactivation radical polymerization techniques.

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