113285-50-0 121088-52-6 12656-76-7 1H,3H-Benzo(1,2-c:4,5-c')difuran-1,3,5,7-tetrone, polymer with 4,4'-oxybis(benzenamine) 25038-81-7 37191-50-7 37890-36-1 79121-88-3 80941-25-9 97955-73-2 Pyromellitic dianhydride, 4,4'-oxydianiline polymer