- Polymer electrolytes have been studied widely, especially poly(ethylene oxide) or PEO that has been blended with other polymers to enhance electrical conductivity and mechanical properties. This research studied polymer blend of PEO and epoxidized natural rubber (ENR) that has epoxide group of 50 % by mole (ENR-50) since ENR has oxygen atom that is flexible and enables ions to move easily. In this work, we used LiSCN and found that at ratio of PEO:ENR at 90:10, electrical conductivity is lower than that of PEO 100 %. However, as the percent of ENR increased, the conductivity increased. At ratio of PEO:ENR at 60:40, the conductivity is still 3 lower than that of PEO 100 % for LiSCN at 5 % and 10 %. However, for LiSCN 2.5 %, conductivity of PEO:ENR at 60:40 is higher than that PEO 100 %. Result from thermal analysis showed that as ENR was added to PEO, the melting temperature of PEO and crystallinity decreased. Additionally, results from X-ray diffraction showed that at ENR was added at 20 % and 40 % the crystallinity of samples decreased. Since ENR is amorphous material, the polymer blend has higher electrical conductivity. However, as we increased the concentration of LiSCN from 2.5 % to 5% and 10 %, the crystallinity decreased, but the conductivity decreased also.