Preparation of Poly(amic acid) and Polyimide via Microwave‐Assisted Polycondensation of Aromatic Dianhydrides and Diamines

Summary: A copolycondesation‐type poly (amic acid) (PAA) was synthesized using pyromellitic dianhydride (PMDA) and 3,3′,4,4′‐benzophenonetetracarboxylic dianhydride (BTDA) as dianhydride monomers, and 4,4′‐oxydianiline (ODA) as a diamine monomer under microwave irradiation in dimethylformamide (DMF). PAA was then converted into a polyimide (PI) by an imidization. The structure and performance of the polymer were characterized by Fourier‐transform infrared (FT‐IR) spectroscopy, Proton nuclear magnetic resonance (1H NMR) spectrometry, viscosity, X‐ray diffraction (XRD), and thermogravimetric (TG) analyses. The results showed that under microwave irradiation, the intrinsic viscosity and the yield of PAA were increases, and the reaction time was shortened. The FT‐IR spectra of the polymer revealed characteristic peaks for PI around 1778– and 1723 cm–1. TG curves indicated that the obtained PI began to lose weight at 535 °C, and its 10% thermal decomposition temperature under N2 was 587 °C.