Polyimides derived from diels‐alder polymerization of furfuryl‐substituted maleamic acids or from the reaction of bismaleamic with bisfurfurylpyromellitamic acids

Certain AB or AA and BB Diels‐Alder polymer precursors bearing maleimide and furan segments were synthesized, characterized, and polymerized. Particularly, the monomaleamic acid derived from 4,4'‐diaminodiphenylmethane, reacted with the monofurfurylpyromellitamic acid to yield a triamic acid which was cyclodehydrated to the corresponding triimide. A polyimide was obtained upon heat‐curing of triimide or the intermediate triamic acid. In addition, equimolar amounts of N , N '‐bismaleimido‐4,4'‐diphenylmethane (BMDM) and bisfurfurylpyromellitimide or their intermediate diamic acids were cured to afford a polyimide. The polymer precursors were characterized by IR and 1 H‐NMR spectroscopy and their curing behavior was investigated by DTA. It was shown that the Diels‐Alder polymerization of monomers took place at lower temperature than that required for crosslinking of BMDM. The thermal stabilities of polymers were ascertained by TGA and isothermal gravimetric analysis (IGA). The synthesized Diels‐Alder polymers were remarkably more heat‐resistant than the crosslinked polymer obtained from BMDM or its intermediate bismaleamic acid. They were stable up to about 360°C in N 2 or air and afforded anaerobic char yield of 58% at 800°C.