Radical homopolymerizations and copolymerizations of 3-[tris(trimethylsilyloxy)silyl]propyl methacrylate (SiMA) in supercritical CO2 were investigated. The homopolymer was obtained in CO2 with a good yield. It was essentially insoluble in pure CO2 at less than 500 bar at 65 degrees C but was soluble in a mixture of CO2 and its monomer (10 w/v %) at 352 bar. The copolymerizations of SiMA with methyl methacrylate, 1,1-dihydroperfluorooctyl methacrylate, and styrene with various monomer feed ratios were also examined in supercritical CO2 and in bulk, and the reactivity ratios were determined.