Mechanism of catalytic acid hydrolysis of aromatic polyimides and relevant polyamic acids

Abstract

SYNOPSISThe kinetics of catalytic acid hydrolysis of N-phenylphthalimide, N-phenylphthalamic acid (model compounds of polyimide and polyamic acids), and of certain soluble polyimides have been studied. A reaction mechanism is proposed implying that unreactive forms of the reactant appear by protonization of the amide bond at the carbonyl oxygen and by dissociation of the o-carboxyl group (in case of N-phenylphthalamic acid). Attack of the nonprotonized amide bond by hydroxonium ions is suggested to be the rate limiting step.A method for determining the cyclization extent of soluble polyimides to within 0.1 "/o is proposed. The effect of structure on the chemical stability of polyimides has been studied.