A quaternary copolymer, containing 1,2,4,5-benzene tetracarboxylic dianhydride (PMDA), 4-aminophenyl ether (ODA), aminopropyldimethyl terminated polydimethylsiloxane (PSX) and 2,5-diaminobenzene sulfonic acid (DABSA), has been successfully synthesized to become an ionic conductor for electrochemical applications. It combines the functions of immobilized anionic groups (SO3-) incorporated into polyimide to increase mobile cation concentration and of PSX introduced to enhance ionic conductivity via flexible chain motion assistance. As a result, an improvement of multiple orders of magnitude for conductivity from each function has been achieved by this copolymer. These conductivities are also confirmed to be of an ionic nature.