Thermal investigation of PVC copolymers for fixed-site proton carrier membranes


Poly(vinyl chloride)s were post-polymerization copolymerized using the strong organic base, piperazine. These aminated products were immobilized and cast as fixed-site proton carrier membranes, and the pH responses were evaluated in appropriate potentiometric cells. Unfortunately, all batches were not of uniform quality and required the measurement of subtle differences in chemistry, which many conventional methods could not distinguish. By making thermal measurements via differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), both the glass transition temperatures (Tg) and the thermal stabilities of different batches were characterized, although not always differentiated. By using the thermally stimulated current (TSC) technique, however, the global relaxation processes of eight batches of poly(vinyl chloride) copolymers could be differentiated, after each powder was polarized, quenched, and reheated. The results of the depolarization current peaks showed that the number of dipoles and/or their associated mobilities differed in otherwise comparable batches and that the best products corresponded to those that displayed pH Nernstian behavior. © 1994.

Publication Title

Thermochimica Acta