Direct methanol fuel cell (DMFC) performance of sulfonated (arylene ether ether nitrile) (m-SPAEEN) copolymers is reported. Low water absorption of m-SPAEEN copolymers enabled increased proton-exchange concentrations in the hydrated polymer matrix, resulting in more desirable membrane properties for DMFC applications. The membrane electrode assemblies (MEAs) using m-SPAEENs showed improved cell properties which could not be obtained by the MEAs using sulfonated polysulfone or Nafion. The DMFC performance using an optimized m-SPAEEN membrane exceeded those of the other membrane systems. For example, 265 mA/cm(2) was obtained for an MEA using m-SPAEEN, compared to 230 and 195 mA/cm(2) for MEAs using sulfonated polysulfone and Nafion membranes, respectively, at 0.5 V, measured under identical conditions. In the comparative evaluations, membrane thickness was selected to give methanol crossover limiting currents that were similar for each of the polymer electrolyte types. Stable cell performance during extended operation (> 100 h) suggested that interfacial compatibility between m-SPAEEN and Nafion-bonded electrodes was good. (c) 2007 The Electrochemical Society.