Synthesis, characterization and kinetic study of hydrolysis of polyamic acid derived from ODPA and m-tolidine and related compounds

Polyamic acid (PAA) and polyimide, 4,4′-oxydiphthalamic acid of m-toluidine (amic acid 1) and bisphthalamic acid of 2,2′-dimethyl-4,4′-diaminobiphenyl (amic acid 2) were synthesized and characterized. In molecular fragmentation study, fast atom bombardment positive ionization mode was found to be suitable than electron impact (EI) ionization mode for detecting the molecular ion of amic acid compounds. EI ionization was found to cause imidization in amic acid compounds. Kinetic investigations were carried out for both amic acid compounds and PAA using potentiometric titration with tetramethyl ammonium hydroxide. At or below 60°C, the acid number was found to increase with increase in time which suggests that hydrolysis reaction is predominant. Acid number was found to decrease with increase in time at 80°C, indicating that imidization reaction is predominant. Rate constants were determined at different temperatures based on the second order rate equation for the hydrolysis reaction. Activation energy was found to be 10.28, 8.34 and 15.05 kcal/mol for the hydrolysis reaction of amic acid compounds 1 and 2 and PAA, respectively.