Ionic association in gel electrolytes of varied polarity as studied by FT Raman spectroscopy

Abstract Ion solvation and ion association in liquid oligo (ethylene glycol) dimethylether ((EG) n DME) lithium triflate solution and in gel type polymer electrolytes of varied polarity have been investigated. The gel electrolytes were prepared by photoinitiated crosslinking homopolymerization of oligo (ethylene glycol) dimethacrylate ((EG) n DMA, n =23) and its copolymerization with acrylonitrile (AN), cyclocarbonatopropylmethacrylate (CPMA) and cyanomethylmethacrylate (CyMA), respectively, in the presence of (EG) 11 DME as plasticizer and LiCF 3 SO 3 . The symmetric stretching mode of the SO 3 group and the lithium–oxygen mode of LiCF 3 SO 3 in these systems were studied as a function of ether oxygen atoms to lithium ratio and temperature by means of Raman spectroscopy. The substitution of the nonpolar methyl end groups of the oligo (ether) by cyanoacetate or cyanoethyl groups causes an increase of the content of free anions in the solution. The contents of free anions observed for (EG) 23 DMA gel networks is lower compared with that of (EG) 11 DME - LiCF 3 SO 3 solutions. The insertion of the polar comonomers AN, CPMA and CyMA into (EG) 23 DMA based networks has been found to enhance the content of free anions.