Determination of the propagation rate coefficient of vinyl pivalate based on EPR quantification of the propagating radical concentration

The propagation rate coefficient (kp) of the vinyl pivalate (VPi) has been determined from an EPR quantification of the concentration of propagating radicals. The polymerizations followed first-order kinetics with respect to the monomer, and the concentration of propagating radicals did not vary with time. The chain lengths were estimated to be sufficiently large to not affect kp. The resulting Arrhenius parameters for kp of VPi in heptane are Ap = 1.39 × 107 dm3 · mol-1 · s-1 and Ep = 20.5 kJ · mol-1. They are very similar to those of vinyl acetate as previously determined by the PLP method. The present results thus indicate that EPR gives consistent kp values for vinyl esters. © 2007 WILEY-VCH Verlag GmbH & Co. KGaA.