Low conversion 4-acetoxy styrene free-radical polymerization kinetics determined by pulsed-laser and thermal polymerization

The free-radical polymerization kinetices of 4-acetoxystyrene (4-AcOS) is studied over a wide temperature range. Pulsed-laser polymerization, in combination with dual detector size-exclusion chromatography, is used to measure k(p), the propagation rate coefficient, between 20 and 110 degrees C. Values are roughly 50% higher than those or styrene, while the activation energy of 28.7 kJ . mol(-1) is lower than that of styrene by 3-4 kJ . mol(-1). With known k(p), conversion and molecular weight data from 4-AcOS thermal polymerizations conducted at 100, 140, and 170 degrees C are used to estimate termination and thermal initiation kinetics. The behavior is similar to that previously observed for styrene, with an activation energy of 90.4 kJ . mol(-1) estimated for the third-order thermal initiation mechanism.