Sulfonated poly(ether ether ketone)/polybenzimidazole oligomer/epoxy resin composite membranes in situ polymerization for direct methanol fuel cell usages

A diamine-terminated polybenzimidazole oligomer (o-PBI) has been synthesized for introducing the benzimidazole groups (BI) into sulfonated poly(ether ether ketone) (SPEEK) membranes. SPEEK/o-PBI/4,4'-diglycidyl(3,3',5,5'-tetramethylbiphenyl) epoxy resin (TMBP) composite membranes in situ polymerization has been prepared for the purpose of improving the performance of SPEEK with high ion-exchange capacities (IEC) for the usage in the direct methanol fuel cells (DMFCs). The composite membranes with three-dimensional network structure are obtained through a cross-linking reaction between PBI oligomer and TMBP and the acid-base interaction between sulfonic acid groups and benzimidazole groups. Resulting membranes show a significantly increasing of all of the properties, such as high proton conductivity (0.14 S cm(-1) at 80 degrees C), low methanol permeability (2.38 x 10(-8) cm(2) s(-1)), low water uptake (25.66% at 80 degrees C) and swelling ratio (4.11% at 80 degrees C), strong thermal and oxidative stability, and mechaniCal properties. Higher selectivity has been found for the composite membranes in comparison with SPEEK. Therefore, the SPEEK/o-PBI/TMBP composite membranes show a good potential in DMFCs usages. (C) 2011 Elsevier B.V. All rights reserved.