Highly compact co-poly(amide-imide)s from polycondensation of an imide-modified derivative of l-aspartic acid

Abstract

The direct polycondensation of a monomer derived from l-aspartic acid together with adipic acid as a modifier co-monomer with aromatic diamines was studied to synthesize co-poly(amide-imide)s (CPAIs). The relative reactivity of the co-monomers and the manner of their insertion into polymer chains were evaluated using a model reaction and 1 H NMR spectroscopy, respectively. The synthesized polymers depicted optical rotations similar to those of the monomer precursor and inherent viscosities in the range of 0.13-0.95 dl/g. Thermal stability and behavior as well as the weight-loss pattern of the CPAIs were studied by thermo-analytical techniques (thermogravimetric analysis-differential thermal analysis, dynamic mechanical thermal analysis and differential scanning calorimetry). Onset decomposition temperatures > 300°C and carbonization residues of more than 50% at 600°C were detected for the treated polymers. Almost all of the copolyamides were noncrystalline solids, as illustrated in the X-ray diffraction patterns, and had good levels of solubility in a variety of polar organic solvents. These polymers could afford transparent and flexible to brittle films in solution casting on glass plates. Scanning electron microscopy on the polymer films showed a uniform and continuous morphology, indicating good film forming ability.