Chitosan/Poly(Amide-Imide) Blend Films: Studies on Thermal and Mechanical Stability, Morphology, and Biodegradability

A diacid monomer was synthesized by the condensation of L-tryptophan amino acid and pyromellitic dianhydride (PMDA). The diacid was utilized for the synthesis of three types of poly(amide-imide)s (PAIs) using three different kinds of diamines. The synthesized monomer and PAIs were characterized using FT-IR, 1H-NMR and 13C-NMR spectroscopies and the PAIs were also used for the fabrication of chitosan (CS)/PAI blend films. XRD patterns of the PAIs, CS and CS/PAI blend films were also studied. Thermal stability of PAIs, CS and CS/PAI samples were studied using thermogravimetric analysis (TGA). The blend samples showed a higher thermal stability compared to the CS film, especially at higher temperatures. Morphology of the CS and blend CS/PAI films were studied before and after the biodegradation by SEM. The mechanical stability studies showed that blend CS/PAI films had a proper mechanical strength and their young’s modulus increased compared to the pristine Chitosan. The in vitro fungal colonization of diacid monomer, PAIs, pure CS and blend CS/PAI samples were performed using Aspergillus niger fungi. After biodegradation, the pure CS showed the highest weight loss of 21.2 wt % among the samples. The blend CS/PAI samples also showed higher weight losses compared to the pure PAIs.