Synthesis and characterization of novel proton-exchange membranes based on poly-1-vinyl-1,2,4-triazole and pyridinesulfonic acid

In this work, acid-base ion-exchange membranes based on poly(1-vinyl-1,2,4-triazole), pyridinesulfonic acid, and polyvinyl alcohol cross-linked with oxalic acid were fabricated and characterized for the first time. A direct relationship between the key physicochemical properties of the membranes and the ratio of polymer components is established. The obtained materials exhibit high thermal and oxidative stability. Their thermal stability was shown to increase with an increase in the poly(1-vinyl-1,2,4-triazole) content, with degradation onset temperatures reaching 340 °C. The membranes also demonstrate high resistance to oxidative degradation in the aggressive environment of Fenton’s reagent. Over time, a gradual weight loss is observed. Thus, following 5 h, the weight losses for poly (1-vinyl-1,2,4-triazole) with pyridinesulfonic acid (20:80), (50:50), (80:20) and the Nafion 212® membrane were 25, 21, 14, and 5%, respectively. Conversely, functional characteristics – such as water absorption, ion-exchange capacity, and proton conductivity – increased significantly with an increase in the content of pyridinesulfonic acid. The maximum specific electrical conductivity of the material reached 250 mS/cm at 80 °C and a relative humidity of 75%. In terms of mechanical properties, an increase in the content of pyridine sulfonic acid leads to an increase in elasticity (elongation at break increases to 54%) and a decrease in elastic modulus (to 50 MPa). These results demonstrate the feasibility of targeted design and property tuning of these membranes to achieve performance exceeding that of the commercial Nafion 212® membrane, making them promising candidates for use as proton-exchange materials in electrochemical devices, including fuel cells.