Theoretical Calculations of Organic Salts and Their Correlation with Proton Conductivity

In the field of high-temperature polymer electrolyte membrane fuel cells, the concern over the proton conductor possible to apply to the high-temperature anhydrous condition has risen. Thus, poly(4-vinylpyridine)s were employed as not only an organic donor polymer with pyridine rings as the base but also heat-resistant materials. We introduced various acids as the acceptors into the polymer side chain through the acid–base reaction to form poly(4-vinylpyridinium salt)s (PVPySAs). The verification that the substituent design as the model in the polymer side chain of PVPySAs by the density functional theory was carried out to discuss what influences their high or low proton conductions. The results indicated that the shortened protonated atomic distance between acid and base moieties enhanced the conductivity of the organic salts. In addition, the pKa and number of protons of the used acid groups give an effect on the proton conductivity.