MADIX polymerization of vinyl acetate using ethyl acetate as a green solvent; near-complete monomer conversion with molecular weight control

Macromolecular Design via Interchange of Xanthates (MADIX) polymerization of vinyl acetate in bulk, or solution polymerization (dichloromethane [DCM] or ethyl acetate) was investigated in order to optimize monomer conversion and achieve molecular weight control. All polymerization reactions were performed using a facile approach using 15 mL glass pressure tubes with Teflon screw cap. In all polymerizations, the ratio of [CTA]₀/[AIBN]₀ was fixed at 1/0.2, the temperature was fixed at 70 °C and the reaction time was fixed at 48 h. The ratio of monomer to MADIX chain transfer agent was varied, starting with 2.0 g of monomer in all polymerizations. First, the MADIX agent S-benzyl-O-ethyl dithiocarbonate was prepared in a single step in 58% yield. Initially, bulk MADIX polymerizations were carried out. In all five polymerizations tested in bulk, the monomer conversion reached a plateau of 81-85% with high reproducibility. The suitability of the green solvent ethyl acetate was also evaluated for the MADIX solution polymerization of vinyl acetate at [M] ₀/[CTA] ₀ ratios from 0 to 400. The MADIX polymerization of vinyl acetate in the green solvent ethyl acetate produced polymers with near-complete monomer conversion, high molecular weights and allowed targeting of molecular weight. The facile polymerization system allows for ideal control of molecular weight and distribution up to 30,000 g mol^-1 and can be adapted to make PVAc up to 100,000 g mol^-1.