Investigation of heterogeneous radical polymerization of methyl methacrylate with polydimethylsiloxane as stabilizing agent in supercritical CO2 by turbidimetry

Experimental results of a turbidimetric in situ investigation of the hetero geneous radical polymerization (dispersion polymerization) of methyl methac rylate and polydimethylsiloxane-monomethacrylate in supercritical carbon di oxide are presented. The experiments were carried out at 60 degreesC and 33 0 bar. Turbidity spectra were measured directly in the autoclave to determi ne the average particle diameter sigma (tau) and the particle density N-AV/ V during the first five minutes of polymerization. The results show that th e particle density increased until a maximum was achieved, whereas the part icle diameter increased during the first stage. Moreover, a comparison with kinetic data suggests that the particles nucleate through coagulation of p olymer that is formed in the homogeneous phase. Copyright (C) 2001 John Wil ey & Sons, Ltd.