High-performance nanostructure chiral poly(amide–imide)s containing benzamide and amino acid linkages: Preparation, characterization and ultrasonic effect on the morphology

Abstract

In this research work, several novel optically active nanostructure poly(amide–imide)s (PAIs) were synthesized from the direct polycondensation reaction of 3,5-diamino- N-(pyridin-3-yl) benzamide with chiral diacids based on trimellitic anhydride-derived dicarboxylic acids containing different natural amino acids such as l-methionine, S-valine, l-alanine and l-isoleucine in green medium consisting of molten tetrabutylammonium bromide. The diamine was synthesized by a two-step reaction. At first, 3,5-dinitro- N-(pyridin-3-yl)benzamide was prepared from the reaction of one equimolar of 3-amino pyridine and one mole of 3,5-dinitrobenzoyl chloride. In the next step, the obtained dinitro was reduced by Pd/C and hydrazine hydrate. The new thermally stable optically active PAIs with inherent viscosity ranging from 0.31 to 0.46 dL g−1 were obtained with high yield. The synthesized polymers were characterized with Fourier transform infrared, proton-nuclear magnetic resonance spectroscopy, specific rotation measurements, thermogravimetric analysis, x-ray diffraction, field emission scanning electron microscopy (FE-SEM) and elemental analysis techniques. Morphological study by FE-SEM showed that these new PAIs were noncrystalline and nanostructure polymers with particle size between 50 and 70 nm. The effect of ultrasonic radiation on the obtained nanostructured polymers showed that the size of polymeric nanoparticles was reduced to about 30–45 nm.