A series of cross-linked network polysiloxanes containing oligoethylene oxide units, (OCH2CH2)(n), as internal free chains have been synthesized by performing hydrosilylation of partially PEO-substituted polysiloxane precursor with alpha, omega-diallyl terminated poly(ethylene glycol). The polymer electrolytes were formed by complexing with LiN(CF3SO2)(2) electrolyte salt and exhibited superior conductive property. The sigma(RT) of the network polymer electrolytes is in the range of 2.50 x 10(-5) to 1.62 x 10(-4) S/cm and depends on the cross-linking density (in terms of Si-H amount of the siloxane precursor), repeating unit number of internal oligoethylene oxide and chain length of the cross-linker. The significant enhancement of the conductivity was observed when low molecular weight dimethyl poly(ethylene glycol) was added as plasticizer. The temperature dependence of the ionic conductivity was also studied, following the Vogel - Tamman - Fulcher (VTF) equation. (C) 2004 Elsevier B.V. All rights reserved.