Ionic transport in a sulfonated polystyrene–polyethylene copolymer

The conductivity of a grafted copolymer composed of 21% sulfonated polystyrene and 79% polyethylene has been investigated as a function of temperature and absorbed moisture for membranes containing the monovalent counterions H + , Li + , Na + , K + , Rb + , Cs, and Ag + . The mobility of Ag + was measured directly in an experiment analogous to that used for the mobility of F ‐centers in alkali halides. The mobility and density of free counterions depend on the amount of absorbed water, but only the mobility and not the density of free counterions is a thermally activated process. Current is carried by both intrinsic counterions and, in samples containing absorbed water with greater than 1.5 V applied, by protonic carriers created when the absorbed water is electrolyzed. Thermal depolarization studies indicate that persistent polarization observed is the result of homogeneous volume polarization, due to the orientation of sulfonic acid side groups.