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 m atrices 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 gamm a -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 spectrosc opy. A significantly stronger lithium coordination was observed when the ge l 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 ob served stronger lithium coordination by (EO)(9) units in the gel, the ion c onductivity was not significantly lower with respect to the gels based on t he other copolymers. (C) 2001 John Wiley & Sons, Inc. J Polym Sci Part B: P olym Phys 39: 1519-1524, 2001.