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Novel nanocomposite films of TiO 2 nanoparticles and hydrophobic polymers having polar groups, poly (bisphenol-A and epichlorohydrin) or copolymer of styrene and maleic anhydride, with high refractive indices, high transparency, no color, solvent-resistance, good thermal stability, and mechanical properties were prepared by incorporating surface-modified TiO 2 nanoparticles into polymer matrices. In the process of preparing colloidal solution of TiO 2 nanoparticles, severe aggregation of particles can be reduced by surface modification using carboxylic acids and longchain alkyl amines. These TiO 2 nanoparticles dispersed in solvents were found not to aggregate after mixing with polymer solutions. Transparent colorless free-standing films were obtained by drying a mixture of TiO 2 nanoparticles colloidal solution and polymer solutions in vacuum. Transmission electronic microscopic studies of the films suggest that the TiO 2 nanoparticles of 3-6 nm in diameter were dispersed in polymer matrices while maintaining their original size. Thermogravimetric analysis results indicate that the nanocomposite film has good thermal stability and the weight fraction of observed TiO 2 nanoparticles in the film is in good accordance with that of theoretical calculations. The refractive index of nanocomposite films of TiO 2 and poly(bisphenol-A and epichlorohydrin) was in the range of 1.58-1.81 at 589 nm, which linearly increased with the content of TiO 2 nanoparticles from 0 to 80 wt %.

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