(US5716727-A)      Casting a solid polymer electrolyte membrane, comprises (i) preparing a solution of the polymer in an acid solvent which further contains a doping acid; (ii) casting the solution to produce a membrane; and (iii) drying the cast membrane.    Also claimed are (1) an acid solution suitable for casting as a polymer electrolyte membrane capable of achieving conductivity levels 3 - 5 times that of similar membranes cast from non-acid solutions under similar conditions, the acid solution comprising an acid solvent capable of dissolving a polymer suitable for use as a solid polymer electrolyte, the polymer, and doping acid suitable for enhancing the high temperature stability of the polymer; (2) casting a solid polymer electrolyte membrane exhibiting enhanced conductivity in methanol/air fuel cell use, comprising casting the polymer from a solution of trifluoroacetic acid (TFA)/H3PO4 containing 300 mol% polymer; and (3) a solid polymer electrolyte membrane comprising an acid solution-cast polymer membrane capable of achieving conductivity above 0.04S/cm in a methanol fuel cell at 130 - 190 C and at water plus methanol pressures of 1 atmosphere.    USE -   The membranes are useful in methanol-air fuel cells (claimed).    ADVANTAGE -   The solid polymer electrolytes have significantly enhanced conductivity. The membranes exhibit excellent oxidative and thermal stability, exhibiting stable chemical and electrical properties up to at least 200 C. They exhibit good mechanical and film properties, high proton conductivity and low fuel permeability, and can conduct protons with very low water activity. They do not suffer from known problems associated with catalyst stability and activity.    (EP907977-A1)      Casting a solid polymer electrolyte membrane, comprises (i) preparing a solution of the polymer in an acid solvent which further contains a doping acid; (ii) casting the solution to produce a membrane; and (iii) drying the cast membrane.    Also claimed are (1) an acid solution suitable for casting as a polymer electrolyte membrane capable of achieving conductivity levels 3 - 5 times that of similar membranes cast from non-acid solutions under similar conditions, the acid solution comprising an acid solvent capable of dissolving a polymer suitable for use as a solid polymer electrolyte, the polymer, and doping acid suitable for enhancing the high temperature stability of the polymer; (2) casting a solid polymer electrolyte membrane exhibiting enhanced conductivity in methanol/air fuel cell use, comprising casting the polymer from a solution of trifluoroacetic acid (TFA)/H3PO4 containing 300 mol% polymer; and (3) a solid polymer electrolyte membrane comprising an acid solution-cast polymer membrane capable of achieving conductivity above 0.04S/cm in a methanol fuel cell at 130 - 190 C and at water plus methanol pressures of 1 atmosphere.    USE -   The membranes are useful in methanol-air fuel cells (claimed).    ADVANTAGE -   The solid polymer electrolytes have significantly enhanced conductivity. The membranes exhibit excellent oxidative and thermal stability, exhibiting stable chemical and electrical properties up to at least 200 C. They exhibit good mechanical and film properties, high proton conductivity and low fuel permeability, and can conduct protons with very low water activity. They do not suffer from known problems associated with catalyst stability and activity.    (US6025085-A)      Casting a solid polymer electrolyte membrane, comprises (i) preparing a solution of the polymer in an acid solvent which further contains a doping acid; (ii) casting the solution to produce a membrane; and (iii) drying the cast membrane.    Also claimed are (1) an acid solution suitable for casting as a polymer electrolyte membrane capable of achieving conductivity levels 3 - 5 times that of similar membranes cast from non-acid solutions under similar conditions, the acid solution comprising an acid solvent capable of dissolving a polymer suitable for use as a solid polymer electrolyte, the polymer, and doping acid suitable for enhancing the high temperature stability of the polymer; (2) casting a solid polymer electrolyte membrane exhibiting enhanced conductivity in methanol/air fuel cell use, comprising casting the polymer from a solution of trifluoroacetic acid (TFA)/H3PO4 containing 300 mol% polymer; and (3) a solid polymer electrolyte membrane comprising an acid solution-cast polymer membrane capable of achieving conductivity above 0.04S/cm in a methanol fuel cell at 130 - 190 C and at water plus methanol pressures of 1 atmosphere.    USE -   The membranes are useful in methanol-air fuel cells (claimed).    ADVANTAGE -   The solid polymer electrolytes have significantly enhanced conductivity. The membranes exhibit excellent oxidative and thermal stability, exhibiting stable chemical and electrical properties up to at least 200 C. They exhibit good mechanical and film properties, high proton conductivity and low fuel permeability, and can conduct protons with very low water activity. They do not suffer from known problems associated with catalyst stability and activity.    (US6099988-A)      Casting a solid polymer electrolyte membrane, comprises (i) preparing a solution of the polymer in an acid solvent which further contains a doping acid; (ii) casting the solution to produce a membrane; and (iii) drying the cast membrane.    Also claimed are (1) an acid solution suitable for casting as a polymer electrolyte membrane capable of achieving conductivity levels 3 - 5 times that of similar membranes cast from non-acid solutions under similar conditions, the acid solution comprising an acid solvent capable of dissolving a polymer suitable for use as a solid polymer electrolyte, the polymer, and doping acid suitable for enhancing the high temperature stability of the polymer; (2) casting a solid polymer electrolyte membrane exhibiting enhanced conductivity in methanol/air fuel cell use, comprising casting the polymer from a solution of trifluoroacetic acid (TFA)/H3PO4 containing 300 mol% polymer; and (3) a solid polymer electrolyte membrane comprising an acid solution-cast polymer membrane capable of achieving conductivity above 0.04S/cm in a methanol fuel cell at 130 - 190 C and at water plus methanol pressures of 1 atmosphere.    USE -   The membranes are useful in methanol-air fuel cells (claimed).    ADVANTAGE -   The solid polymer electrolytes have significantly enhanced conductivity. The membranes exhibit excellent oxidative and thermal stability, exhibiting stable chemical and electrical properties up to at least 200 C. They exhibit good mechanical and film properties, high proton conductivity and low fuel permeability, and can conduct protons with very low water activity. They do not suffer from known problems associated with catalyst stability and activity.