In the first project, poly(vinyl chloride) (PVC)/silica (SiO 2 ) anocomposites (NCs) were prepared. Firstly, for decreasing the agglomeration of SiO 2 nanoparticles and improving their compatibility with the polymer matrix, the surface of SiO 2 () was modified with vitamin B 1 (VB 1 ) as a biocompatible coupling agent. The interaction between and VB 1 was confirmed by several techniques including FT-IR, XRD, FE-SEM, TEM, and TGA. From comparing of the TGA curve of the modified SiO 2 with its pure form, the presence of VB 1 on the surface of was proved. Based on the XRD patterns, the surface modification had no effect on the crystalline structure of the SiO 2 . The FT-IR analysis showed grafting of VB 1 on the surface of SiO 2 . The Morphology observations (TEM analysis) confirmed the reduction of average particle size of SiO 2 after the surface modification. Then 3, 5, and 7 wt% of the modified nanoparticles were added to the PVC matrix and PVC/SiO 2 nanocomposite films were prepared under ultrasonic irradiation as a fast, economical and environmentally friendly method. The resulting nanocomposites were characterized using several techniques including FT-IR, XRD, FE-SEM, TEM, TGA, UV-Vis spectroscopy, mechanical, and water contact angle measurement testing. The normal distribution curve showed the nanometer scale dispersion of nanoparticles in the polymer matrix. Also, the mean size of the nanoparticles was estimated 18 nm. The TGA results displayed an increase in the thermal stability of the nanocomposite films in comparsion with the neat polymer. According to the UV-Vis spectrum, the nanocomposite films exhibited more absorption in comparison with the pure polymer. The result of the contact angle measurement showed an increase in the hydrophilicity. In the second project, poly(vinyl alcohol) (PVA) was used as a polymer matrix and PVA/SiO 2 NC films were prepared by the addition of 3, 5, and 7 wt% of the modified SiO 2 to the PVA matrix under ultrasonic irradiation. The resulting nanocomposites were characterized using different techniques including FT-IR, XRD, FESEM, TEM, TGA, UV-Vis spectroscopy, mechanical, and water contact angle measurement test. The TEM and FE-SEM images showed a spherical morphology and uniform dispersion of the nanoparticles in the polymer matrix. According to the TGA thermograms, the addition of the nanoparticles into the polymer matrix leads to an increase in its thermal resistance and hydrophilicity. Also, the mechanical properties of PVA were improved.