In an effort to fabricate stretchable, superionic, hydrophobic, stable solid-state polymer electrolyte membrane (PEM), polyethylene glycol-b-polypropylene glycol-b-polyethylene glycol dimethacrylate (PPPDA) photocurable precursor was synthesized. This precursor was used in ternary mixtures consisting of ethylene carbonate (EC) plasticizer, and lithium trifluorosulphonyl imide salt (LiTFSI) which were melt-mixed to obtain isotropic solution over a wide compositional range. On photopolymerization, the ternary mixture formed a completely amorphous and transparent membrane. This polymer membrane exhibits ionic conductivity of about 10^-3 S/cm, improved thermal and moisture resistance, and superior tensile properties as compared to the polyethylene glycol diacrylate (PEGDA) based PEMs. The polymeric membrane showed a wide electrochemical window on testing with half cells consisting of stainless steel (SS)/PEM/Li Foil. In order to evaluate the electrochemical performance of the polymeric membranes, half cells comprising LiFePO₄/PEM/Li foil were tested using cyclic voltammetry and charge/discharge cycling performance.