Sulfonated dimethyl fumarate (SDMF) was prepared. Poly(ethylene oxide) (PEO) with sodium sulfonate side chains (SPEO) was synthesized by transesterification between SDMF and PEO with molecular weights of 200, 400, 600, 800, and 1000. The SPEO was subsequently mixed as a plasticizer with PEO polyurethane (PU). Samples were characterized by elemental analysis, FTIR, H-1-NMR, gel permeation chromatography, and impedance analysis. The mixture exhibited a homogeneous domain. The maximum conductivity of the CPU1000/SPEO600 was 2.6 x 10(-7) S cm(-1) at room temperature. The relation between the ionic conductivity and the temperature was in agreement with the Arrhenius equation.