A vibrational spectroscopic study of lithium triflate in polyphosphazenes with linear oligoethyleneoxy side-chains of different lengths

Abstract

A comparative vibrational spectroscopy study is reported for a series of polymer electrolytes composed of poly(oligoethyleneoxy phosphazenes) containing dissolved lithium triflate. These polymers, of the form [NP((OCH 2CH 2) x OCH 3) 2] n , with x=0, 1, 2, or 5, have been mixed with LiCF 3SO 3 in oxygen:lithium concentration ratios ranging from 10:1 to 40:1. Raman vibrational spectroscopy has been used to examine ionic association and local changes of the polymer as the salt concentration and the length of the ethylene oxide side-chains vary. The degree of ionic association of the triflate ion increases with increasing salt concentration. At a given salt concentration, the degree of ionic association and the nature of the ion-polymer interaction are dependent on the length of the side-chains.