in this thesis, a new optically active poly(amide-imide) (pai) was synthesized by the indirect polycondensation reaction of the l-phenylalanine based diacid chloride and 4,4?-diaminodiphenylether in the presence of triethylamine in n-methyl-2-pyrrolidone. the formation of pai was confirmed by ftir, 1h nmr and elemental analysis. in next step, the surface of titanium dioxide (tio2) nanoparticles was treated with a silane coupling agent of ?-aminopropyl-triethoxy silane (kh550). tio2 is one of the most potential materials, nontoxicity and chemical inertness that cause wide applications in the fields of electronic and photonic. tio2 has three crystalline polymorphs: rutile, anatase and brookite .the most common form of bare tio2 crystal that used in many industries such as paints and cosmetics is rutile that stable at high temperatures. the anatase to rutile transition is an irreversible procedure and usually generated within a temperature range of 500-1000oc. tio2 nanocomposites have many applications especially in medicine, cleaning machining, jointing and chemistry industry. other application fields of them are ultraviolet light, absorbent coating, interference filter, antireflective coating, and optical waveguides.then pai and surface modified tio2 nanoparticles were used to produce a polymer based bionanocomposites (bnc)s via ultrasonic irradiation process. obtained bncs were characterized by means of fourier transformation infrared spectroscopy, x-ray diffraction, thermogravimetric analysis (tga), scanning electron microscopy (sem), field emission scanning electron microscopy and transmission electron microscopy (tem). the results obtained from tem and sem micrographs showed that the nanoparticles are homogeneously dispersed in pai matrix on 30-50 nm. tga analysis of the pai/tio2 bncs shows the great improvement in thermal stability parameter of the bncs related to pure pai. cloisite na+ as a kind of mmt is a hydrous alumina silicate mineral that made from octahedral alumina sheet between two tetrahedral silicate sheets and ions holding between the layers. it shows a net negative charge on the lamellar surface. surface properties of natural clays can be modified by simple ion exchange process with organic cations such as quaternary ammonium cations. during of this modification, the clay changes from hydrophilic to hydrophobic as well as organophilic and is converted to an organoclay. the inorganic nanolayers of cloisite na+ was modified with ammonium salt of l-valine amino acid (val) and then it was dispersed in poly(vinyl alcohol) (pva) matrix. pva is a synthetic, nontoxic, tasteless, biocompatible, water solubility and semicrystalline hydrophilic polymer. the pva/cloisite na+/val bionanocomposites (bnc)s were prepared by solution intercalation technique using ultrasonic irradiation. the reaction between this novel organically modified cloisite na+ and pva occurred by the hydrogen bonding and hydrophobic interactions. the basal spacing of the cloisite na+/val was studied by x-ray diffraction. the thermal stability and optical clarity of pva and pva/cloisite na+/val are also studied by tga and uv–visible transmission spectra, respectively. tga results show that using cloisite na+/val in the pva matrix improved the thermal stability property of the resulting bnc films. the morphological image of synthesized materials was studied by scanning electron microscopy, and transmission electron microscopy. the nanocomposite structure study specified a coexistence of exfoliated and intercalated cloisite na+/val layers in the pva matrix.