The influence of the poly(ethylene oxide) (PEO) chain length on the thermal properties and manner of ion coordination in PEO-LiCF3SO3 electrolyte mixtures has been examined. The same form of ethoxy ... Li+ ... CF3SO3- coordination is observed for polyethers ranging from high molecular weight (MW of 4x10(6)) to triglyme with only four ethoxy segments. The melting points of the PEO and P(EO)(3):LiCF3SO3 phases are similar with MWs of 2000 and higher, but are lowered considerably for PEO with MWs below 2000. These differences may be directly attributed to the larger fraction of methoxy chain ends present for the lower MW polymers which disrupt the ordered structures as thermal energy increases. (C) 2012 Elsevier B.V. All rights reserved.