Preparation and characterization of novel aromatic polyimides having 4,5-di(1,3-phenylene)imidazole structure

Novel diamines 4,5-di(3-aminophenyl)imidazol (1), 4,5-di(3-aminophenyl)-2-methylimidazole (2), and 4,5-di(3-aminophenyl)-2-phenylimidazole (3) were prepared, and novel aromatic polyimides were synthesized by ring-opening polyaddition of aromatic tetracarboxylic dianhydrides to the diamines, followed by thermal cyclodehydration. The inherent viscosities of the polyamic acids ranged from 0.37 to 0.98 d lg(-1). Glass transition temperatures (T(g)s) of the polyimides were found in the range from 279 to 353 degrees C, and weight residues at 600 degrees C were above 82%. Interestingly, although polyimide 10c derived from 3 and 3,3'4,4'-biphenyltetracarboxylic dianhydride (4c) has a side pendant phenyl group, the T-g of 10c was approximately 30 degrees C higher than that of the corresponding polyimide derived from 1 and 4c, which do not have the side pendant. Some polyimides exhibited good solubility. Particularly, 10c was soluble in pyridine at room temperature and m-cresol at 80 degrees C at 2.0% (w/v) as well as possessing high thermal resistance supported by the T-g of 346 degrees C and the weight residue at 600 degrees C of 87%. (C) 1998 Elsevier Science Ltd. All rights reserved.