1,5-dimethylpolyphenylenoxide was brominated with NBS up to a substitution degree of 80%. The brominated PPO (BrPPO) was cross-linked with DABCO to a covalent cross-linked membrane. To investigate the influence of the size of the network, additional diiodobutane (DIB) was used. It could be determined that the ion conductivity (Cl-) with additional DIB rises from 2.3 mS/cm to 5.4 mS/cm despite a higher hydrophobicity of the DIB membranes. An IEC around 1 meq/g was reached and the methanol uptake was lower than 20%. The alkaline stability was investigated at 90 degrees C in 1 M KOH and all membranes showed a constant stable behaviour. The first DMFC measurement using a non precious FeCo/C catalyst on the cathode led to an excellent performance of 132 mW/cm(2). (c) 2012 Elsevier B.V. All rights reserved.