Introducing a new generation of anion conducting membrane using swelling induced fabrication of covalent methanol barrier layer

Abstract

Layer-by-layer (LBL) assembly is one of the most universal membrane coating practices today to reduce the fuel (e.g., methanol) crossover problem in fuel cells. However, scientific uses of traditional LBL assemblies are obstructed by the fluid-demanding and laborious nature of the method. We report an approach to the fabrication of layered anion exchange membranes (AEMs) containing covalent methanol barrier layer that is based on swelling phenomena. We demonstrate that, using the swelling phenomena, layered membranes can be fabricated by simply immersing a haloalkylated polymer (brominated poly-(2,6-dimethyl-phenylene oxide) (BPP)) based membrane in aqueous dimethylamine for a definite time (10–60 min), followed by immersing the intermediate membrane in aqueous trimethylamine, or vice-versa. Two different and unique layered membrane morphologies can be attained by just altering the assembly conditions for creation of the barrier layer on/in the quaternized BPP (QPP) matrix in which the QPP layer mainly provides ionic conductivity; the layer assembly creates highly fuel blocking layer that covalently linked with the QPP layer, individually providing the mechanical support and fuel blocking features of the layered membrane. The fabricated AEM exhibits excellent dimensional stability and high strength but low methanol permeation relative to the parent QPP membrane.