Monitoring dispersion polymerisations of methyl methacrylate in supercritical carbon dioxide

This paper describes the development and application of power compensation calorimetry equipment to monitor the dispersion polymerisation of methyl methacrylate in supercritical carbon dioxide. We have studied the polymerisation of methyl methacrylate using a macromonomer (poly(dimethylsiloxane) monomethacrylate) as stabiliser and initiator azoisobutylnitrile. The calorimetric data allow monitoring of the polymerisation process. Through monitoring the changes in reaction exotherm and system pressure during the polymerisation one can clearly observe the point at which the polymerisation starts and effectively ceases. The effect of initiator concentration and stabiliser on the reaction was studied and the enthalpy of polymerisation obtained from the apparatus was found to correlate with previously reported data.