The polymer electrolytes composed of poly(acrylonitrile-co-lithium methacrylate) [P(AN-co-LiMA)], ethylene carbonate (EC), and LiClO4 salts have been prepared. The ion groups in the P(AN-co-LiMA) were found to prevent EC from crystallization through their ion-dipole interactions with the polar groups in the EC. This suppression of the EC crystallization could lead to the enhancement of the ion conductivity at subambient temperature. The polymer electrolytes based on the PAN ionomer with 4 mol % ion content exhibited ion conductivities of 2.4 x 10(-4) S/cm at -10 degrees C and 1.9 x 10(-3) S/cm at 25 degrees C by simply using EC as a plasticizer. In the polymer electrolytes based on the PAN ionomer, ion motions seemed to be coupled with the segmental motions of the polymer chain due to the presence of the ion-dipole interaction between the ion groups in the ionomer and the polar groups in the EC, while the ion transport in the PAN-based polymer electrolytes was similar to that of the liquid electrolytes.