Polymer membranes with high ionic conductivity are important for various applications, including lithium batteries. The mechanical and conductive properties were decoupled through a second, non-conductive component. This was achieved through the use of poly(styrene)-block-poly(ethylene oxide) (PS-PEO) copolymers, where PEO forms the conducting ion channels and PS provides the rigid matrix. The ionic conductivity of these nanostructured electrolytes was comparable to that of the conducting part of the copolymer, and the elastic modulus was mainly governed by the hard insulating phase. The conductivity of the copolymers increased with the molecular weight of the PEO block, although the conductivity of homopolymer PEO decreased with increasing molecular weight. The role of structure on the ionic conductivity of these materials was determined. The lithium salt segregated itself to the middle of the conductive channels, and this effect was more pronounced for higher molecular weight copolymers. Thinner lithium lamellae lead to higher ionic conductivity. This is an abstract of a paper presented at the AIChE Annual Meeting (Salt Lake City, UT 11/4-9/2007).