In this project at first, poly(vinyl alcohol) (PVA) was chemically modified by the introduction of different amount of N -phthaloyl-L-phenylalanine. The modification was carried out by the reaction of PVA hydroxyl groups with (2S)-3-phenyl-2-phthalimidylpropanoyl chloride using N , N -dimethyl acetamide/lithium chloride as a reaction media. The novel copolymers obtained were characterized by spectroscopic techniques, elemental analysis, X-ray diffraction and thermal methods. Optical rotation and viscosities were also measured. The degree of esterification was determined by 1 H-NMR. The influence of reagent molar ratio on the degree of modification was also evaluated. Thermal stability of the copolymers was checked by thermogravimetric analysis and differential thermogravimetric analysis. All copolymers displayed improved thermal stability compared to the parent polymer. In the second part, the surface of titanium dioxide (TiO 2 ) nanoparticles was modified with ?-aminopropyltriethoxy silane as a coupling agent. Then a new kind of poly(vinyl alcohol)/titanium dioxide (PVA/TiO 2 ) nanocomposites coating with different modified TiO 2 loading were prepared under ultrasonic irradiation process. Finally, these nanocomposites coating were used for fabrication of PVA/TiO 2 films via solution casting method. The TEM and SEM results indicated that the surface modified nanoparticles were dispersed homogeneously in PVA matrix on nanoscale and based on obtained results a possible mechanism was proposed for ultrasonic induced nanocomposite fabrication. TGA confirmed that the heat stability of the nanocomposite was improved. UV-visible spectroscopy was employed to evaluate the absorbance and transmittance behavior of the PVA/TiO 2 nanocomposite films in the wavelength range of 200-800 nm. The results showed that this type of films could be used as a coating to shield against UV light. Finally, Novel poly(amide-imide)/TiO 2 bionanocomposites containing L-isoleucine moiety were prepared via a simple and inexpensive ultrasonic irradiation process. Poly(amide-imide) as a source of polymer was synthesized by direct polycondensation reaction of N -trimellitylimido-L-isoleucine with 4,4?-diaminodiphenylsulfone in the tetrabutyl ammonium bromide/triphenyl phosphite as a green solvent system. Due to the tendency for agglomeration, the surface of TiO 2 nanoparticles was modified with ?-aminopropyltriethoxyl silane. Through TEM photographs, it can be found that the surface modified TiO 2 nanoparticles with diametric size of less than 40 nm, uniformly dispersed in the PAI matrix.