New polymer electrolyte films, polyethylene oxide (PEO)-LiClO4 complex containing a cascade (branched) nitrile conductivity enhancer, C6H5CH2N(CH2CH2CN)(2), 2CN, or C6H5CH2N[CH2CH2CH2N(CH2CH2CN)(2)](2), 4CN, were prepared by casting acetonitrile solution containing PEG, LiClO4, and the enhancer, 2CN or 4CN. Conductivity increased from 4.94 x 10(-7) S cm(-1) for (PEO)(20)(LiClO4) at 30 degrees C to 1.35 x 10(-5) S cm(-1) with the addition of 2CN forming (PEO)(20)(LiClO4)(2CN)(2), and to 4.69 x 10(-6) S cm(-1) with the addition of 4CN forming (PEO)(20)(LiClO4)(4CN)(0.5). Addition of the cascade nitriles, 2CN and 4CN, increased the conductivity of the PEO-LiClO4 complex by dissolution of lithium salt with the terminal nitrile groups.