Tetramethoxysilane (TMOS) or tetraethoxysilane (TEOS), an organic monomer [methylmethacrylate (MMA) or styrene (St)] and either alpha-propylmethacryloxy-omega-trimethylsiloxy-oligo(dimethylsiloxane) (OMS), as a compatibilizing agent, or alpha,omega-bis(vinyl) oligo(dimethylsiloxane) (OVS), as compatibilizing and crosslinking agent, were allowed to undergo a sol-gel reaction under acidic condition and in the presence of 2,2'-azoisobutyronitrile (AIBN) as a free-radical initiator. The hydrolysis-condensation and in situ free-radical polymerization occur independently, to give a hybrid consisting of both inorganic and organic components. The conversion of the monomers to the proper polymers was monitored by IR spectroscopy and TGA. The resistance of the organic polymers to solvent extraction was also studied. The hybrids were pyrolyzed in an oxidative atmosphere. By decomposition, the organic polymer generated pores in the inorganic matrix. A quantitative evaluation of the characteristics for the resulting porous material was made by determination of the specific area, pore volume, and average radius. (C) 2003 Wiley Periodicals, Inc.