Synthesis, characterization, and properties of new polystyrene-SiO₂ hybrid sol-gel materials

A new family of organic-inorganic hybrid materials has been prepared by incorporating polystyrene structure units covalently into the SiO₂ glass network via the sol-gel approach. The polymer precursors were synthesized by free-radical copolymerization of styrene with 3-(trimethoxysilyl)propyl methacrylate (MSMA) at various feeds. These copolymers were then hydrolyzed and co-condensed with tetraethyl orthosilicate in tetrahydrofuran at room temperature to afford monolithic polystyrene-SiO₂ hybrid sol-gel materials having SiO₂ contents of 15 to 84% by weight. The hybrid materials derived from the copolymers with MSMA contents greater than 22 mol% have excellent optical transparency. In these transparent hybrid materials, the polymer chains should be uniformly distributed in and covalently bonded to the amorphous SiO₂ matrices. The bulk properties of these materials including density, refractive index, and hardness were found to be related to their molecular compositions and can be tailored by varying the polymer contents.