Preparation and characterization of composite membranes with ionic liquid polymer-functionalized multiwalled carbon nanotubes for alkaline fuel cells

Multiwalled carbon nanotubes functionalized with an imidazolium-type ionic liquid polymer, PIL(BF4)-MWCNTs, have been successfully prepared via in situ free radical polymerization of 1-vinyl-3-methylimidazolium iodide ([VMIm][I]) and then blended with poly(2,6-dimethyl-1,4-phenylene oxide) containing imidazolium groups (PPO-MIm) in solution to fabricate composite membranes. The composite membranes were characterized by scanning electron microscopy (SEM) and the SEM images of the membranes show that the PIL(BF4)-MWCNTs can be homogeneously dispersed in the PPO-MIm matrix. The conductivity and mechanical properties of the composite membranes were examined. It was demonstrated that the incorporation of the PIL(BF4)-MWCNTs into the membranes of PPO-MIm can increase both conductivity and mechanical properties. The composite membrane containing 0.3 wt% of PIL(BF4)-MWCNTs (P(0.3)) exhibits a dramatic enhancement in ionic conductivity (95.3%) and tensile strength (82.9%) in comparison with the membrane without PIL(BF4)-MWCNTs. Therefore, this research demonstrates that the incorporation of functionalized carbon nanotubes is a facile and useful strategy for improving both ionic conductivity and mechanical properties of alkaline polymer electrolyte membranes.