Single ion conducting blend polymer electrolytes were prepared from borate complex polymers containing fluoroalkane dicarboxylate and two methoxy [oligo(ethylene oxide)] side chains and poly(ethylene oxide) (PEO). Mechanical properties were greatly improved by blending with PEO. Ionic conductivity was dependent on the chain length of oligoether groups, and decreased with increasing PEO content. The optimized blend polymer B (n = 7.2)-PEO (80:20 wt.%) exhibited ionic conductivity of 2 x 10(-6) S cm(-1) at 30degreesC. (C) 2004 Elsevier Ltd. All rights reserved.