Types of Polymeric Electrolyte Anion Exchange Membranes: Heterogeneous and Grafted Membranes, Interpenetrating Polymer Networks and Homogeneous Membranes

This chapter covers an overview of the types of polymeric electrolytes that are or can be used in AEMFCs, water electrolyzer, CO 2 electrolyzer, etc. Most AEMs can be divided into heterogeneous membranes, grafted membranes, interpenetrating polymer networks, and homogeneous membranes based on their chemical structures and preparation procedures. This chapter discusses the design principles, synthetic routes, structure–property relationships, performance in device, and encountered problems. Generally, a heterogeneous membrane is defined as an ion-conducting material embedded in an inert matrix. The membrane is an ion-solvating polymer when the matrix is a polymer. The heterogenous membrane is called a hybrid membrane when it is composed of an organic and an inorganic segment such as silane and graphene oxide. A grafted membrane consists of polymer backbones and ion-containing side chains. An interpenetrating polymer network is a polymer comprising two or more networks which are at least partially interlaced at the polymer level but are not covalently bonded to each other. In a homogeneous membrane, the cationic groups are covalently bonded to the polymer matrix. Generally, the synthetic routes to homogenous membranes can be categorized into two pathways: direct polymerization of cationic monomers and/or comonomers, and post polymerization functionalization, in which the cationic moieties are introduced into the polymer matrix.