Aqueous emulsions of cationic polyurethane ionomers, based on poly(epsilon-caprolactone glycol) as soft segment, isophorone diisocyanate as hard segment, 3-dimethylamino-1,2-propanediol as chain extender and potential ionic center, and hydrochloric acid as neutralizer, were mixed with tetraethoxysilane to prepare silicon dioxide-polyurethane (SiO2/PU) nanocomposites by a sol-gel process during which the inorganic mineral is deposited in situ in the organic polymer matrix. The sizes and distributions of the particles were measured by dynamic light scattering, and the structure and morphology of the nanocomposites were observed by transmission electron microscope and FTIR spectrum. (C) 2004 Wiley Periodicals, Inc.