Pressure Dependence of the Propagation Rate Coefficient kp for Vinyl Acetate Polymerizations in Bulk and in Solution of Fluid CO2

The propagation kinetics of vinyl acetate (VAc) free-radical homopolymerization in bulk and in solution of 40 wt % CO 2 have been studied by the PLP−SEC method at pressures up to 1500 bar. The molecular weight distributions of the polymer samples show well-resolved pulsed-laser-induced structure with at least two, in most cases even three, distinct inflection points. At the p and T conditions of this work, no difference is seen in propagation rate coefficients, k p, of VAc in solution of carbon dioxide and in bulk. The activation volume for k p at 25 °C in both reaction media is Δ V # = −(10.2 ± 0.9) cm 3 mol -1 .