SYNTHESIS AND ELECTROCHEMICAL CHARACTERIZATION OF CROSS-LINKED POLY(ETHYLENE OXIDE) CONTAINING LIN(CF3SO2)(2)

The ionic conductivity of polymeric electrolyte systems comprising a n etwork of poly(ethylene oxide) (PEO) crosslinked with urethane functio ns and containing LiN(CF3SO2)(2) (TFSILi), was studied. Polyurethanes based on three different PEO molecular weights were prepared. Diffusio n studies of TFSILi in swollen PEO-urethane membranes with acetonitril e were performed showing a diffusion coefficient for PEO2000 higher th an that observed with LiClO4 in the same material, and were correlated with the variation of T-g's of the dried membranes which were determi ned as a function of salt concentration and crosslink density. The inf luence of a salt molecule on the T-g (for the TFSILi charged membranes ) is equivalent to 25% of the influence of a covalent crosslink in the range of molecular weight between crosslinks used in this study. The relatively high slope for the plot T-g(-1) vs salt concentration for t he network in PEO600 allows to consider a high chain rigidification du e to the introduction of salt. The conductivity of network based on PE O2000 with a molar concentration ratio O/Li = 43 reached 10(-5) S cm(- 1). (C) 1997 Elsevier Science Ltd.