Efficient stirring is needed to realize heat flow anal. with a thermally homogeneous medium. Because dispersion polymn. with supercrit. fluids can be destabilized under stirring, a preliminary target has been to find a compromise between synthesis and basic reaction calorimetry requirements. This paper describes the use of poly(dimethylsiloxane) macromonomer with a mol. wt. 5000 g/mol as stabilizer for the dispersion polymn. of Me methacrylate in supercrit. carbon dioxide. The effect of stirring speed and stabilizer concn. has been examd. This study has shown that PMMA can be produced at high yield and mol. wt. using 10 wt. % (with respect to monomer) PDMS macromonomer at stirring speeds up to 600 rpm. A polymn. enthalpy of -57.6+-2 kJ/mol has been calcd. being in good agreement with previously reported data. Thus, preliminary results for the heat balance using the newly developed high pressure reaction calorimeter for supercrit. fluid applications have shown the important potential of reaction calorimetry to promote supercrit. fluid technologies at industrial scale allowing for the detn. of kinetics and thermodn. and safety data, resp.