Molecular dynamics (MD) simulations have been made of the crystalline short-chain LiPF6 center dot PEO6 system to probe structural ordering for (EO23 M-w - 1059) host polymer. Five different different chain-end arrangements for a methyl-terminated monodisperse poly(ethylene oxide) start structures have been studied, two "smectic" and three "nematic", to represent different types of relative alignment of the end-groups between adjacent PEO chains, and different chain-end coordination situations to the Li-ions. One particular situation is found to result effectively in Li-ion bridging between PEO chains along the chain axes, thereby creating continuous ion transport pathways across the chain breaks. This situation is also found to give rise to Li+-PF6-ion-pairing and Li-O coordination instabilities in the end-group regions, where coordination to Li-ions would appear to have a more radical influence on local structure than the issue of smectic VS. nematic end-group alignment. It could be that such structural situations involving bridging Li-ions (in both smectic and nematic arrangements) are a necessary condition for the promotion c of Li-ion transport in the chain direction. Comparison of simulated and experimental XRD profiles is concluded to be an inappropriately crude and uncertain technique for distinguishing between possible short-chain ordering models. (c) 2007 Elsevier Ltd. All rights reserved.