Nanostructured amino acid containing poly(amide-imide) (PAI) was synthesized from the direct polycondensation reaction of 2–(3,5–diaminophenyl)–benzimidazole and N,N′–(pyromellitoyl)–bis–phenylalanine diacid under green condition by using tetrabutylammonium bromide as molten ionic liquid. Field emission scanning electron microscopy images show that the average diameter of polymeric nanoparticles with spherical shape was around 20–35 nm. In the next step, these polymeric nanoparticles were used as nano-fillers for reinforcement of poly(vinyl alcohol) (PVA) for the first time. Bionanocomposite of PVA and various compositions of PAI nanoparticles were produced through ultrasound-assisted technique. Fourier transform infrared spectroscopy, x-ray diffraction, field emission scanning electron microscopy, and thermogravimetric analysis were utilized to characterize the obtained hybrid materials, morphology, and properties. Results of thermal properties indicated that the thermal stability is enhanced. The improvement of thermal properties was attributed to the homogeneous and good dispersion of PAI nanoparticles in the PVA matrix and the strong hydrogen bonding between O–H groups of PVA and the carbonyl of amide and imide groups of the used PAI nanoparticles.