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.