The synthesis and properties of the organic polymersilica nanocomposites by blending perhydropolysilazane with organic polymer having hydroxyl groups have been described. Poly(methyl methacrylate) (PMMA)-silica nanocomposites with a PMMA/silica lamellar structure and spherical silica domains in a PMMA matrix were obtained with random copolymers and block copolymers. The effect of the architecture of the random and block copolymers on the morphology of composites has been summarized. The thermal stability, electrical properties, such as field break down, leakage current, etc., and surface hardness of the composites have been discussed. (c) 2006 Wiley Periodicals. Inc.