Mesomorphic Polymer Hydrogel Stabilizing Ionic Surfactant Self-Assembly for Fuel Cells

Abstract

Lyotropic self-assembly of ionic surfactants benefits the construction of ion-conductive pathways but suffers from poor mechanical stability owing to the intrinsic fluidity. Here, a novel mesomorphic polymer hydrogel, featuring a porous network of the cross-linked polymer trapping lyotropic self-assembly of ionic surfactants, is presented for fuel cells. The mesomorphic hydrogel, which is facilely derived from radical polymerization of an acrylamide monomer and a cross-linker in an aqueous solution of 1-tetradecyl-3-methylimidazolium hydrogen sulfate, exhibits not only a lamellar lyotropic liquid crystal phase but also reversible tensile, compressive, and shear deformations. Macroscopic alignment of the mesomorphic hydrogel is achieved by low-frequency shear, and ionic conductivity is promoted to 166 mS cm–1 by virtue of the aligned ion-conductive channels. A hydrogen fuel cell is fabricated from the mesomorphic polymer hydrogel, and a peak power density of 48 mW cm–2 is achieved. Overall, this work provides a strategy to endow functional lyotropic self-assembly with mechanical strengths for diverse electrochemical applications.