Controlled synthesis of branched poly(vinyl acetate)s by xanthate-mediated RAFT self-condensing vinyl (co)polymerization

Abstract

An original xanthate possessing a vinyl ester polymerizable function, namely vinyl 2-[(ethoxycarbonothioyl)sulfanyl]propanoate (Xa2), was synthesized. It was implemented as a chain transfer agent (CTA) to design branched polymers based on vinyl acetate (VAc) by self-condensing vinyl copolymerization (SCVC) by reversible addition–fragmentation chain transfer (RAFT). The branching density as well as the length of the branches were efficiently tuned by adjusting the total initial concentration of polymerizable functions C₀ = [VAc]₀ + [Xa2]₀ and the ratio C₀/[Xa2]₀. Additionally, Xa2 was also homopolymerized to provide hyperbranched oligomers. These precursors were used as multifunctional CTAs to control a subsequent polymerization of VAc, affording starlike poly(vinyl acetate)s (PVAcs). All the products were characterized by ¹H NMR spectroscopy, quadruple detection size exclusion chromatography and differential scanning calorimetry. Reference samples consisted of linear PVAcs which were synthesized using a homologue non-polymerizable xanthate. As expected, the intrinsic viscosity and the glass transition temperature increased when either the number of branches or their length increased.