Design and synthesis of a novel quinoxaline diamine and its polyimides with high-Tg and red color

Abstract To produce high-temperature polyimide (PI) films meeting the demand of flexible-display, heteroaromatic monomers were extensively investigated. Quinoxaline is one kind of the most important N-heterocycles, which possesses pharmacological activities and thermotolerance. In this work, newly designed diamine monomer 3/2-(4-aminophenyl)-2/3-methylquinoxalin-6-amine (QMDA) was successfully synthesized. Their corresponding quinoxaline-containing PI films were prepared by cooperating QMDA with several aromatic dianhydrides, and divided into two series according to different thermal imidization procedures. The firm scaffold of quinoxaline was proved to enhance the thermal stability of the obtained PIs. The effect of final annealing temperature on molecular packing and thermal properties of the PI films was also investigated. Under higher annealing temperature, PI films were found to pack more tightly due to the formation of more cross-linkings in polymer matrix. The restriction of chian movements brought these PIs higher T g more than 500 °C or even prevented the occurace of glass transition.