Amphiphilic polymer gel electrolytes. II. Influence of the ethylene oxide side-chain length on the gel properties

Amphiphilic polymers consisting of copolymethacrylates carrying about 26 wt % ethylene oxide [(EO)(n)] side chains of different lengths were used as matrices in gel electrolytes. The gel electrolytes were composed of 30 wt % copolymer and 70 wt % 1 M LiPF6 in a mixture of ethylene carbonate and gamma -butyrolactone (2/1 w/w). The coordination of lithium ions by the (EO)(n) side chains in competition with the solvent was studied by Raman spectroscopy. A significantly stronger lithium coordination was observed when the gel electrolyte was based on a copolymer carrying (EO)(9) units in comparison with copolymers having (EO)(1), (EO)(2), and (EO)(4) units. Despite the observed stronger lithium coordination by (EO)(9) units in the gel, the ion conductivity was not significantly lower with respect to the gels based on the other copolymers. (C) 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1519-1524, 2001.