IONIC ASSOCIATION IN GEL ELECTROLYTES OF VARIED POLARITY AS STUDIED BY FT RAMAN-SPECTROSCOPY

Ion solvation and ion association in liquid oligo (ethylene glycol) di methylether ((EG)(n)DME) lithium triflate solution and in gel type pol ymer electrolytes of varied polarity have been investigated. The gel e lectrolytes were prepared by photoinitiated crosslinking homopolymeriz ation of oligo (ethyleneglycol) dimethacrylate ((EG)(n)DMA, n = 23) an d its copolymerization with acrylonitrile (AN), cyclocarbonatopropylme thacrylate, (CPMA) and cyanomethylmethacrylate (CyMA), respectively, i n the presence of (EG)(11)DME as plasticizer and LiCF3SO3. The symmetr ic stretching mode of the SO3 group and the lithium-oxygen mode of LiC F3SO3 in these systems were studied as a function of ether oxygen atom s to lithium ratio and temperature by means of Raman spectroscopy. The substitution of the nonpolar methyl end groups of the oligo (ether) b y cyanoacetate or cyanoethyl groups causes an increase of the content of free anions in the solution. The contents of free anions observed f or (EG)(23)DMA gel networks is lower compared with that of (EG)(11)DME - LiCF3SO3 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. (C) 1998 Published by Elsevier Science Ltd. A ll rights reserved.