Solid-Supported MADIX Polymerization of Vinyl Acetate

Abstract

A simple, one-pot synthesis of a surface-tethered MADIX agent was established via the reaction of 1,1′-thiocarbonyl diimidazole (TCDI) with a thiol, followed by reaction with the hydroxyl groups of a Wang resin. The supported RAFT agent was used to control the polymerization of vinyl acetate in toluene. The amount of surface-bound polymer was found to greatly increase with increasing content of solid MADIX agent, reaching values of almost 80%. The grafted PVAc chains were cleaved from the Wang resin support via radical reaction with tert-amyl peroxy acetate (TAPA), and the molecular weight distributions exhibited the typical shape of polymers formed via a well-controlled living radical polymerization (LRP), with the free polymers showing a slightly higher molecular weight than the living fraction. The Mn values of both living polymer fraction (surface-bound polymer) and dead polymer (free polymer) increased steadily with monomer conversion—as expected for a well controlled MADIX polymerization—and were in good agreement with the theoretical molecular weights. PDI values of both polymer fractions scatter around 1.5, with a slight tendency of narrower molecular weight distributions of the living polymer, which shows a minimum value of 1.43. Addition of free MADIX agent to the solution phase led to a decrease in PDI values of both free and bound polymer, and the experimental molar masses were in very good agreement with theoretical predictions.