A novel series of PVA/DPA-4-SASS/SiO2 composite membranes were fabricated and characterized in the present study. Compared to the neat PVA, water uptake, proton conductivity, and ion exchange capacity of the membranes were enhanced. The membrane containing 5 Wt. % of SiO2 nanoparticles and 80 Wt. % of the DPA-4-SASS showed the highest values of water uptake, proton conductivity (1.5 × 10−1 S/cm) and ion exchange capacity (1.47 mmol/g). The results also indicated that methanol permeability was decreased by increasing the DPA-4-SASS content in the hybrid membranes. Thermal stability and mechanical properties of the crosslinked membranes were also improved.