Polycarbonate nanocomposite containing silicon oxide nanoparticles average size of 5 nm at different weight ratio has been prepared by solution mixing method. The dispersion of nanoparticles in polymer matrix was studied by transmission electron microscopy (TEM). The optical and thermally stimulated behavior of nanocomposites were analyzed by energy dispersive X-ray spectra (EDX), X-ray diffraction pattern (XRD), UVvis spectroscopy, differential scanning calorimetry (DSC), and thermally stimulated discharge current (TSDC). TEM images show the dispersion and size of the nanoparticles, however, EDX indicate the presence of SiO2 on the surface of the nanocomposite film. An XRD result reveals that the crystallinity increases with increase in concentration of SiO2 nanoparticles in polymer matrix. The direct and indirect optical energy band gaps decreased and number of carbon atom increased with concentration of SiO2 nanoparticles. We have observed that the increase of SiO2 nanoparticles in PC significantly reduces the refractive index. DSC and TSDC show that glass transition temperature increases according to SiO2 weight ratio. The TSDC of nanocomposites samples could be understand in terms of non-Debye theory of charge relaxation and co-tunneling mechanism of charge transport. (c) 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012