A new comb-like copolymer, poly(vinylidene fluoride-co-hexafluoropropylene)-g-poly(methyl methacrylate), or [P(VDF-HFP)-g-PMMA], was successfully synthesized through grafting in situ formed PMMA to the P(VDF-HFP) backbone. The composition of the P(VDF-HFP)-g-PMMA copolymer was characterized by Fourier transform infrared spectroscopy (FTIR), thermal gravimetric analysis (TGA) and elemental analysis. X-Ray diffractometry (XRD) and differential scanning calorimetry (DSC) were used to examine the reduction in crystallinity of P(VDF-HFP) due to the anchoring of PMMA segments on it. Gel electrolyte membranes based on the resulting copolymer were prepared by. the Bellcore process. The ionic conductivity of Li+ across the membranes and the related transference number were measured. A study of the interfacial stability between Li electrode and the P(VDF-HFP)-g-PMMA get electrolyte was also conducted to evaluate the suitability of the P(VDF-HFP)-g-PMMA copolymer in rechargeable lithium and lithium-ion battery applications.