PROPERTIES OF GEL ELECTROLYTES BASED ON CROSS-LINKED COPOLYMERS OF OLIGO(ETHYLENE GLYCOL) DIMETHACRYLATE AND CYANOMETHYL METHACRYLATE

Gel electrolyte films were prepared from oligo(ethylene glycol) dimeth acrylate ((EG)(n)DMA, n = 23) and cyanomethyl methacrylate (CyMA) by p hotoinitiated in situ copolymerization in the presence of oligo(ethyle ne glycol) dimethylether ((EG)(n)-DME, n = 11) and LiCF3SO3. The influ ence of the content of CyMA in the copolymer on the ionic association of LiCF3SO3 as well as on the thermal and electrochemical properties o f the gels was studied. About 80mol% CyMA in the copolymer network cau ses a relatively high dissociation degree of LiCF3SO3 (approximate to 50%), cationic transference numbers t(+)approximate to 0.5 and an anod ic stability up to 5V. The ionic conductivity a shows a maximum around 20 mol% CyMA attaining sigma x 10(-4) S/cm at ambient temperature. Th e decrease of sigma at higher contents of CyMA in the crosslinked poly mer is attributed to the insertion of substantial parts of (EG)(11)DME into the copolymer network and to a chain stiffening effect of CyMA. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.