Kinetics of alkaline hydrolysis of a polyimide surface

The alkaline hydrolysis of a polyimide (PMDA-ODA) surface was studied as a function of time, temperature and hydroxide ion concentration. Quantification of the number of carboxylic acid groups formed on the modified polyimide surface was accomplished by analysis of data from contact angle titration experiments. Using a large excess of base, pseudo-first-order kinetics were found, yielding k(obs) approximate to 0.1-0.9 min(-1) for conversion of polyimide to poly(amic acid) depending on [OH-]. From the dependence of k(obs) on [OH-], a rate equation is proposed. Conversion of the polyimide surface to one ofpoly(amic acid) was found to reach a limiting value with a formation constant, K, in the range 2-10 L.mol(-1).