THERMO-OXIDATIVELY STABLE POLYIMIDES AND THEIR CHEMICAL STRUCTURES

A series of aromatic diamines having ether and/or carbonyl moieties in their structures were synthesized. By using these synthesized diamine s and commercially available tetracarboxylic dianhydrides, various kin ds of polyimides having ether and/or carbonyl moieties were synthesize d. The thermo-oxidative stability of the obtained polyimides was inves tigated by focusing on the chemical structures of their repeating stru cture units. The reason for the improved thermo-oxidative stability of the ether-carbonyl polyimide structure was explained by an electronic ally balanced condition, i.e., the balance of electron donor moiety (- O-) and electron acceptor moiety (-CO-) in a chemical structure, and t he degree of electron deficiency of the benzene-imide ring structure. The possibility of the formation of a charge transfer complex (CT-comp lex) was also mentioned as an explanation of the improved thermo-oxida tive stability of ether-carbonyl polyimide structures. (C) 1998 John W iley & Sons, Inc.