1H,3H-Benzo(1,2-c:4,5-c')difuran-1,3,5,7-tetrone, polymer with 1,4-benzenediamine and 5,5'-carbonylbis(1,3-isobenzofurandione) 28157-66-6 p-Phenylenediamine, pyromellitic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride polymer