Proton-Conducting Polymer Membrane Consisting of Cross-Linked Poly(2-hydroxyethyl methacrylate) with Nafion® for Fuel Cell Application

To increase the water retention and proton-conducting ability of Nafion (R), we prepared a cross-linked polymer consisting of poly(2-hydroxyethyl methacrylate) (pHEMA) and Nafion (R). pHEMA was chosen as a cross-linking polymer because it produces a water-insoluble but water-swellable polymer. Although it is hydrophobic, its water-swellable characteristic means that water will not be excluded from the polymer. Introduction of pHEMA into Nafion (R) prevents polymer solubility and provides structural stability and rigidity, which should in turn reduce the methanol permeability. Moreover, convenient permeability of pHEMA to cations makes it a good candidate for a hydrocarbon proton-conducting polymer tuned with Nafion (R).