A series of organic-inorganic hybrid materials have been prepared by copolymerizing styrene and alkoxysilane-methacrylate via the sol-gel process. The alkoxysilane-containing copolymer precursors were synthesized by free-radical copolymerization of styrene with an alkoxysilane-containing monomer, methacrylic acid 3-(trimethoxysilyl)propyl ester (MAMSE), at several feeds. The copolymer precursors were then hydrolyzed and condensed to generate PS-SiO 2 hybrid sol-gel materials. The hybrid copolymers possess excellent optical transparency and a nanoscale microphase separation. The copolymer precursors and their hybrid copolymers were characterized by FT-IR spectra, 1 H NMR spectra, DSC, and TGA thermograms. Chemical structural effect on the morphology and thermal properties was investigated with SEM, mapping photographs, and high-resolution solid state 1 3 C and 2 9 Si NMR spectra. It was found that compatibility between copolymer and silica mainly comes from incorporating the polymer with silica covalently. Moreover, MAMSE could be hydrolyzed to methacrylic acid and ester-interchanged to silyl methacrylate during heat treatment. This also enhances the compatibility between the copolymer and silica. The thermal properties of the PS-SiO 2 hybrid copolymers are improved as silica content increase. However, the presence of silyl ester groups, which were formed during heat treatment, would reduce the thermal stability of the hybrid copolymers.