The advancement of energy technology and electrocatalysis, particularly in hydrogen fuel cells, requires robust and cost-effective proton exchange membranes. While polyvinyl alcohol (PVA) is a promising candidate due to its film-forming properties, its inherent water solubility severely limits its performance in harsh acidic environments. Addressing the growing demand for sustainable precursors in polymer synthesis, this study presents the development of highly stable, crosslinked PVA bio-based membranes utilizing furfural as the primary crosslinking agent and sulfosuccinic acid (SSA) as a functionalizing co-crosslinker.
A systematic evaluation of the synthesis conditions, specifically the solution reaction temperature and furfural concentration was conducted, catalyzed by p-toluenesulfonic acid and followed by thermal curing. The structural modification was confirmed via FTIR-ATR, evidencing successful acetalization through the formation of C–O–C ether linkages, alongside the incorporation of furan rings and proton-conducting sulfonic groups. Dimensional stability was assessed over three consecutive swelling-drying cycles. The results revealed that the ternary system synthesized with 100% furfural and SSA at 70 °C exhibited the most robust network, maintaining a low and stable water uptake of 26%. Furthermore, this optimized formulation demonstrated exceptional chemical resistance, recording a negligible weight loss of less than 4% after 7 days of immersion in acid, whereas the neat PVA membrane completely dissolved. Thermogravimetric analysis (TGA and DTG) corroborated this structural enhancement; although SSA functionalization introduced an early degradation step associated with desulfonation, the thermal collapse of the crosslinked polymer backbone was drastically delayed from 318 °C in neat PVA to 437 °C in the optimized membrane, significantly increasing the final char yield.
Overall, this synergistic crosslinking strategy successfully transforms water-soluble PVA into a structurally rigid, highly acid-resistant, and thermally stable membrane, demonstrating significant potential for demanding electrochemical applications.