An investigation of the kinetics of copolymerization of methyl methacrylatep-methyl styrene to high conversion: Modelling diff″sion-controlled termination and propagation by free-volume theory

An experimental investigation of the kinetics of the free radical copolymerization of methyl methacrylate (MMA) and p-methylstyrene (PMS) initiated with azobisisobutyronitrile (AIBN) was conducted at temperatures of 60°C and 80°C. Three levels of initiator concentration and initial monomer composition were studied. Conversions were measured gravimetrically and by gas chromatography (g.c.) and the weight average molecular weight (M̄w) by low-angle laser light scattering photometry (LALLSP). A kinetic model using free volume theory seems adequately to account for diffusion-controlled termination and propagation. The model also accounts for segmental-diffusion control of termination at low conversions and termination by reaction diffusion at high conversions. Model predictions are in reasonable agreement with published data on homopolymerization of MMA (ref. 1) as well as with data on copolymerization of these monomers reported herein. This model should find use in the design, simulation, optimization and control of polymer reactor systems for the production of MMA/PMS copolymers.