In this study, glycidyl methacrylate was copolymerized with poly(ethylene glycol) methyl ether methacrylate to obtain a copolymer {poly[glycidyl methacrylate-poly(ethylene glycol) methyl ether methacrylate] [P(GMA-PEGMA)]}, which was crosslinked with alpha,omega-diamino poly(propylene oxide) (Jeffamine) at various weight ratios and molecular weights to form novel gel polymer electrolytes (GPEs). The crosslinked copolymers were characterized by Fourier transform infrared spectroscopy and thermal analysis. The crosslinked polymers were amorphous in the pristine state and became crystallized after they were doped with lithium electrolyte. Furthermore, the crosslinking degree of the crosslinked polymers increased with increasing weight ratio of Jeffamine, and both the swelling properties and mechanical behaviors of the crosslinked polymers were heavily affected by the weight ratio and molecular weight of Jeffamine. The ionic conductivity (sigma) of the GPEs from the crosslinked copolymers was determined by alternating-current impedance spectroscopy. A higher molecular weight and increased weight ratio of Jeffamine resulted in a higher sigma. The GPE based on P(GMA-PEGMA) crosslinked with an equal weight of Jeffamine D2000 exhibited the highest sigma of 8.29 x 10(-4) S/cm at 25 degrees C and had a moderate mechanical strength. These crosslinked copolymers could be potential candidates for the construction of rechargeable lithium batteries. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 120: 2979-2984, 2011