<p>A series of poly(vinyl alcohol) (PVA) based membranes for high temperature proton exchange membrane fuel cells are synthesized via a simple aldol condensation reaction. Three aldehyde compounds with alkaline groups, including 4-(bromomethyl)benzaldehyde grafted with 1-methylimidazole (QBMB-MeIm), 4-pyridinecarboxaldehyde (4PCA), and 4-(1H-imidazol-1-yl)benzenecarbaldehyde (4IBA), are grafted onto the PVA main chain, while glutaraldehyde (GA) is used as a crosslinking agent to improve the mechanical properties of the membranes. A systematic investigation was conducted on these crosslinked membranes to evaluate the influence of different side-chain groups and crosslinking degrees on their properties. The imidazole and pyridine groups on the PVA side chains enhance phosphoric acid (PA) absorption, resulting in excellent proton conductivity and acid doping capability. Among the synthesized membranes, PVA-4IBA-20%GA exhibits the best performance, achieving 220% PA uptake when immersed in 85 wt% PA at 30&#xa0;°C. It also demonstrates a tensile strength of 3.7 MPa and a conductivity of up to 0.158 S cm⁻¹ at 150&#xa0;°C. These findings highlight the significant potential of PVA-based membranes for HT-PEMFC applications, offering a promising avenue for future energy technologies.</p>