Organicinorganic nanocomposites consisting of co-poly(vinyl chloride-vinyl acetate-vinyl alcohol) and silica were prepared via solgel process. Two types of hybrids were prepared, one in which interactions between hydroxyl group present in the copolymer chain and silanol groups of silica network were developed. In the second set, extensive chemical bonding between the phases was achieved through the reaction of hydroxyl groups on the copolymer chains with 3-isocyanatopropyltriethoxysilane (ICTS). Hydrolysis and condensation of tetraethoxysilane and pendant ethoxy groups on the chain yielded inorganic network structure. Mechanical and thermal behaviors of the hybrid films were studied. Increase in Young's modulus, tensile strength, and toughness was observed up to 2.5 wt % silica content relative to the neat copolymer. The system in which ICTS was employed as binding agent, the tensile strength and toughness of hybrid films increased significantly as compared to the pure copolymer. Thermogravimetric analysis showed that these nanocomposite materials were stable up to 250 degrees C. The glass transition temperature increases up to 2.5 wt % addition of silica in both the systems. Field emission scanning electron microscope results revealed uniform distribution of silica in the copolymer matrix. (c) 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012