COORDINATION OF OH END-GROUPS IN THE POLYMER ELECTROLYTE SYSTEM LIX-PPG FOR X=PF6-, BF4-, CLO4-, CF3SO3-, I-, BR- AND CL-

End-group coordination has been studied using poly(propylene glycol) with a molecular weight of 3000 (PPG(3000)) terminated with hydroxy groups. On dissolution of different lithium salts LiX in PPG(3000) for X = PF6-, BF4-, ClO4-, CF3SO3-, I-, Br- and Cl-, shifts of the OH stretching band were observed using Fourier transform infra-red spectroscopy. The size of the shift is dependent on the strength of the hydrogen bond formed between the OH group and the anion of the salt. A cation dependence of the OH stretching band was also found using KPF6. There are two dominating coordination structures involving the OH groups present in the samples. One is a solvent-separated ion pair where the anion and cation are separated by an OH end-group, and the other is an OH group coordinated both to the cation of the salt and to an ether oxygen from the polymer.