Organotellurium-Mediated Radical Polymerization of Chloroprene

Controlled radical polymerization of chloroprene (Cp) was achieved using organotellurium-mediated radical polymerization (TERP). Bulk polymerization of Cp employing a TERP chain transfer agent (CTA) 1 in the presence of diphenyl ditelluride and AIBN afforded polychloroprene (PCp) with controlled molar masses up to Mn = 60,100 and low dispersities (Đ < 1.4) by regulating the monomer conversion. Reaction monitoring, macro-CTA stability tests, and mass spectrometric analysis strongly suggest that termination of polymer-end radicals by combination occurs as a side reaction and gradually increases at high monomer conversions. By limiting the conversion to ∼70% or lower, macro-CTAs retaining sufficient chain-end fidelity were obtained. These macro-CTAs enabled efficient block copolymerization with methyl methacrylate (MMA) or styrene (St), yielding well-defined block copolymers. Notably, block copolymerization of Cp from PMMA or PSt macro-CTAs proceeded much more efficiently than that using PCp macroinitiators, yielding structurally highly controlled diblock copolymers. This study establishes a viable controlled radical polymerization platform for Cp and represents the first successful synthesis of block copolymers incorporating PCp segments.