Porous membranes based on acrylonitrile/methyl methacrylate copolymer were prepared by a phase-inversion method. Microstructures of the porous membranes were controlled through the variation of the evaporation drying time before immersion in a nonsolvent bath. Gel polymer electrolytes were prepared from these porous membranes via soaking in an organic electrolyte solution. They encapsulated the electrolyte solution well without solvent leakage and maintained good mechanical properties that allowed the preparation of thin films (similar to23 mum). These systems showed acceptable ionic conductivity values (>6.0 X 10(-4) S/cm.) at room temperature and sufficient electro-chemical stability over 4.4 V that allowed applications in lithium-ion polymer batteries.