The synthesis of a thermally stable proton conducting polymer based on poly(phenylene oxide) (PPO) was carried out using 2,6-dimethylphenol (DMP) and 2-allylphenol (AP) as monomers. The copolymers using the two monomers were prepared with DMP to AP molar ratios of 20:80, 40:60, 60:40, and 80:20. The polymers and the copolymers were blended with poly(vinylidene fluoride) and cast as membranes. All the membranes were sulfonated and characterized for their suitability as a polymer electrolyte membrane.