A Xanthate-Type Photofunctional Chain Transfer Agent for the Synthesis of Macrophotoinitiators

Abstract

Polystyrene (PSt), poly(methyl methacrylate) (PMMA), and poly(vinyl acetate) (PVAc) macrophotoinitiators with well-defined structures comprising a photoreactive group, benzoin (B), at the chain end were successfully synthesized by RAFT/MADIX polymerization. First, a photofunctional xanthate-type chain transfer agent (B-CTA) was produced by an efficient two-step one-pot synthesis. Then, B-CTA was used in the RAFT/MADIX polymerization of styrene (St), methyl methacrylate (MMA), acrylonitrile (AN) (more activated monomers), and vinyl acetate (VAc) (a less activated monomer). Based on spectral and GPC data, the RAFT/MADIX polymerizations of St, MMA, and VAc monomers produced well-controlled macrophotoinitiators with narrow molecular weight distributions and compatible theoretical and experimental number-average molecular weights. The resulting well-defined macrophotoinitiators, B-PSt, B-PMMA, and B-PAVc, were used as precursors to obtain block copolymers PSt-b-PCHO, PMMA-b-PCHO, PVAc-b-PCHO from cyclohexene oxide (CHO) and PSt-b-PBVE, PMMA-b-PBVE, PVAc-b-PBVE from butyl vinyl ether (BVE) monomers, respectively, via photoinduced free radical promoted cationic polymerization. Various analyses such as elemental, spectroscopic, and GPC techniques were used to confirm the structures of the synthesized molecules.