Ionic Liquid Crystalline Composite Membranes Composed of Smectic Imidazolium Hydrogen Sulfate and Polyvinyl Alcohol for Anhydrous Proton Conduction

Proton exchange membranes are widely used in fuel cells for directly converting chemical energy into electrical energy. Commercially successful perfluorosulfonic acid membranes do not have the ability of proton conduction under dry conditions. Owing to the advantages of simplified thermal and water management, anhydrous proton conductive materials are appealing. Herein, a novel liquid crystalline composite membrane is prepared by a solution cast method for anhydrous proton conduction at elevated temperatures. Linear polyvinyl alcohol acts as main chain, and mesomorphic imidazolium hydrogen sulfate molecules containing a rigid mesogen act as side chains to form a side-chain like liquid crystalline composite. Furthermore, the composite membrane can be macroscopically aligned through unidirectionally shearing to promote anhydrous proton conduction. The composite exhibits a conductivity of 2.8 x 10(-4) S cm(-1) at 150 degrees C and a tensile strength up to 6.7 MPa. The ionic liquid crystalline composite offers a facile way to achieve ordered molecular arrangement in membranes for proton conduction at elevated temperatures.