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Application of chiral diacid N-trimellitylimido-L-valine for the surface modification of copper oxide as inorganic filler and preparation of poly(amide–imide)/cupric oxide nanocomposites
In this study, the thermally stable poly(amide–imide) (PAI)/cupric oxide (CuO) nanocomposites (NCs) containing 4, 6 and 8 wt% of CuO nanoparticles (NPs) were prepared by ultrasonic technique. At first, the optically active PAI was synthesized from the polymerization of a chiral monomer, N-trimellitylimido-L-valine, with 4,4′-methylenebis(3-chloro-2,6-diethylaniline) in a green medium using molten tetra-n-butylammonium bromide and triphenyl phosphite. Then, in order to prevent agglomeration of NPs and to obtain high compatibility between the NPs and the polymer matrix, the surface of the CuO NPs was successfully modified using a bioactive diacid containing L-valine amino acid. Finally, PAI/CuO NCs were produced via sonochemical reaction. The resulting NCs were characterized by means of Fourier transform infrared spectra, x-ray diffraction, thermogravimetric analysis (TGA), field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy techniques. FE-SEM results showed that the CuO NPs were homogeneously dispersed in the PAI matrix without agglomeration for NC 4 wt%. However, with increasing in the percentage of CuO NPs, some aggregations were observed. The TGA curves indicated that the obtained PAI/CuO NCs are thermally more stable than the pure PAI. The shielding ability of modified CuO NPs and PAI/CuO NCs was also investigated by ultraviolet–visible spectroscopy.