Blend membranes based on sulfonated poly(phenylene oxide) for polymer electrochemical cells

In a solid polymer electrolyte membrane fuel cell containing an ion-exchange polymer membrane as electrolyte sandwiched between an electrochemically reactive porous anode and cathode, the improvement in which the ion-exchange polymer membrane comprises a blend of a homogeneously sulfonated poly(phenylene oxide) and poly(vinylidene fluoride), the homogeneously sulfonated poly(phenylene oxide) having a chemical structure characterized by the following recurring unit:

• ##STR3## wherein R.sub.1 and R.sub.2 are each selected from the group consisting of H, SO.sub.3 H and SO.sub.3 M;
• and M is a metal selected from the group consisting of an alkali metal, an alkaline earth metal and a transition metal, and n is an integer greater than 40, the homogeneously sulfonated poly(phenylene oxide) having a number average molecular weight between about 15,000 and about 10,000,000 and an ion charge density between about 1 and about 3.9 meq/g, the poly(vinylidene fluoride) having a number average molecular weight between about 10,000 and about 10,000,000, the weight ratio of homogeneously sulfonated poly(phenylene oxide) to poly(vinylidene fluoride) in the blend being greater than about 1/49 and less than about 19/31, the fuel cell capable of having a current density between about 1 A/cm.sup.2 and about 2 A/cm.sup.2 at 0.5 V, while using a minimum catalyst loading equivalent to between 0.1 mg/cm.sup.2 and 0.2 mg/cm.sup.2 of platinum on a platinum/carbon polytetrafluoroethylene electrode at 30 psi reactant gases, and a cell a temperature between 45.degree. C. and 85.degree. C.