One-pot synthesis of semicrystalline polyamide imide based on 4,4’-diaminobenzanilide and 2,2-propylidene-bis(1,4-phenyleneoxy)diphthalic anhydride in molten benzoic acid

High-temperature thermoplastic semicrystalline polyamide imide (PAI) with T_g = 250°C, and T_m = 370°C was synthesized from 4,4’-diaminobenzanilide, and 2,2-propylidene-bis (1,4-phenyleneoxy) diphthalic anhydride using three different methods: one-pot high-temperature catalytic polycondensation in molten benzoic acid (BA), low-temperature polycondensation (LTP) in dimethylacetamide (DMAA) followed by chemical imidization, and LTP followed by imidization. The influence of the synthetic route on the crystallinity of PAI was studied by wide-angle X-ray scattering. The PAI synthesized in molten BA comprised a reactive oligomer, which on heating up to 360°C easily transformed into high-molecular-weight PAI. The thermal and rheological properties of the high-molecular-weight PAI thus prepared were studied using differential scanning calorimetry, trimellitic acid, thermogravimetric analysis, and capillary viscosimetry. The rheological characteristics indicate that the obtained PAI can be melt processed by extrusion and hot pressing at 370–380°C.