Polymer electrolyte membranes (PEM) have been fabricated from various star-shaped poly(ethylene glycol) macromonomers to investigate the effect of chain-branching architectures on thermal, mechanical, and electrochemical properties. The PEM prepared from the 4-arm star macromonomer network revealed the lowest glass transition temperature (T-g), the highest modulus, elongation-to-break, and tensile strength relative to those prepared from 3-arm star and linear macromonomers. On the same token, the PEM based on the 4-arm PEG showed the highest ionic conductivity and good capacity retention.