In our study, for ion-polymer interaction in gel-type polymer electrolyte (GPE), two kinds of ions were used. GPE systems were composed of Mg or Li salt, organic solvent (gamma-BL), and polymer matrix prepared by chemical crosslinking of NBR with poly(ethylene glycol)methylethermethacrylate (PEGMEM) having polar group (-CH2-CH2-O-) in the side chain of monomer. GPE consisting of Li+ ion had higher ionic conductivity than that of Mg2+ ion at below 100 wt.% of electrolyte content (I M salt/gamma-BL). On the other hand, GPE consisting of Mg2+ ion had higher ionic conductivity than that consisting of Li+ ion at over 120 wt.% of electrolyte content (1 M salt/gamma-BL). The maximum liquid electrolyte content was 200 wt.% for all GPE systems. And the highest ionic conductivity of 3.3 x 10(-2) S cm(-1) was achieved for the case of Mg (2+)-GPE with 200 wt.% of liquid electrolyte contents at 20degreesC. The interaction between ionic species and polymer matrix in GPE was investigated by using Fourier transform infrared spectroscopy (FT-IR). Also, cyclic voltammogram of Mg2+-GPE confirmed the electrochemical property of divalent cation with two electron-transfer reactions. (C) 2004 Elsevier Ltd. All rights reserved.