Solid solutions of blends of poly(ethylene oxide) (PEO) and epoxidized natural rubber (ENR) comprising 12 wt %, of LiClO4 were studied. Two glass transition temperatures, corresponding to the T(g)s of the constituents, confirm immiscibility of the polymers over the entire composition range. It turns Out that the T(g)s of both polymers slightly increase after addition of salt to the blends. This shift is approximately constant over the whole range of blend composition. Accordingly, T-g measurements reveal that the salt dissolves to approximately equal relative amounts in the two phases. The degree of crystallinity of PEO in blends with ENR descends only to a minor extent with ENR content. However, addition of salt leads first to decreasing crystallinity and second this decrease becomes more pronounced with the addition of ENR. It shows that under these experiment conditions the salt content in PEO increases as compared to ENR. As one expects, the rate of isothermal crystallization does not change in blends as long as PEO is in excess. The situation changes again when salt is added. The rate decreases in a certain range of crystallization temperatures when ENR is added, demonstrating that salt is favorably dissolved in PEO. Conductivity was measured in polymers comprising different salt concentrations. A power-law dependence of conductivity on salt concentration was found. It results that the mobility of charge carriers in PEO exceeds that of ENR by five orders of magnitude. Therefore, the conductivity in blends is primarily governed by PEO as long as PEO is in excess. conductivity measurements reveal again that salt is preferably dissolved in PEO. The distribution coefficient is estimated. (C) 2008 Wiley Periodicals, Inc.