Cation coordination in ion-conducting gels based on PEO-grafted polymers

Ionic conducting polymer gels prepared from PEG-grafted acrylates, ethylene carbonate (EC), dimethyl carbonate (DMC), and LiPF6 are studied by means o f infrared and Raman spectroscopy. It is found that the presence of grafted PEO chains substantially changes the coordination of lithium cations from 'cation-solvent' to 'cation-polymer'. Spectroscopic studies show that Li+-P EO coordination is strongly favored in competition with the solvent molecul es and dominates completely at ether oxygen to Li-cation ratios (O:Li) of 1 0:1 and 5:1. At an O:M of 4:1 a solvent-cation interaction arises, in agree ment with previously reported MD calculations of a preferred coordination n umber of 5 in similar systems. The results suggest that the complex interac tions which determine long time stability and ionic transport properties ca n be designed by functionalization of the polymer backbone in PMMA-based ge l electrolytes. O 2000 Elsevier Science B.V. All rights reserved.