Unlike the quaternary alkyl ammonium cationic groups, a nucleophilic displacement or a Hofmann degradation will not occur on the imidazolium cationic groups under high pH conditions and a relatively high temperature. There is no b hydrogen in the 1,3-alkyl substituted imidazolium cationic groups with a big p bond conjugated system. Therefore, the imidazolium cationic groups could stay stable under high pH conditions. As a result, the membranes prepared in this work showed excellent chemical stability and oxidative stability.