Thermal stability of poly(4,4'-methylenedianiline) salts and their bases

Poly(4,4'-methylenedianiline) (PMDA) salts have been synthesized by chemical polymerization of 4,4'-methylenedianiline using five different protonic acids. The salts were converted into their bases by using aqueous ammonium hydroxide. The thermal stabilities of the salts and bases have been determined from thermogravimetric analysis. The PMDA salts undergo a three-step weight loss process. The water molecules escape from the polymer matrix in the first step, followed by the loss of low molecular weight fragments and finally the decomposition of the polymer backbone occurs. The activation energy for the polymer degradation process has been calculated using two different methods. The polymer bases are slightly more stable than their corresponding salts.