An acid-base proton conducting polymer blend membrane is provided. The acid-base proton conducting polymer blend membrane comprises a first acidic polymer having acidic subunits, a second basic polymer having basic subunits, and a third polymer containing one or more functional units for improving membrane conductivity, flexibility, water remaining ability, dimension stability, and methanol crossover. In one embodiment, the acid-base polymer blend membrane of the present invention comprises a first acidic polymer having acidic subunits, a second basic polymer having basic subunits, wherein at least one of the first acidic and second basic polymer comprises one or more functional units to improve the properties of the membrane. The functional units include hydrophilic units, methanol blocking units, methanol blocking units, dimensional stabilizer units, and flexible units.