Investigating the nanostructure and thermal properties of chiral poly(amide-imide)/Al2O3 compatibilized with 3-aminopropyltriethoxysilane

Novel chiral poly(amide-imide) (PAI)/Al2O3 nanocomposites were prepared via incorporating surface modified Al2O3 nanoparticles into polymer matrices for the first time. In the process of preparing the nanocomposites, severe aggregation of Al2O3 nanoparticles could be reduced by surface modification and γ-aminopropyltriethoxysilane. The optically active PAI chains were formed from the polycondensation reaction of N,N′-(pyromellitoyl)-bis-phenylalanine diacid with 2-(3,5-diaminophenyl)-benzimidazole in green condition. The obtained polymer and inorganic metal oxide nanoparticles were used to prepare chiral PAI/Al2O3 nanocomposites through ultrasonic irradiation. The resulting nanoparticle filled composites were also characterized by Fourier transform infrared spectroscopy, X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy and thermogravimetric analysis (TGA) techniques. TGA thermographs confirmed that the heat stability of the prepared nanoparticle-reinforced composites was improved. Mechanical properties showed that the film containing 10 wt% of modified Al2O3 had a tensile strength of the order of 83.6 MPa, relative to the 64.3 MPa of the pure PAI.