CATIONIC TRANSPORT IN GEL ELECTROLYTES ON BASIS OF OLIGO(ETHYLENE GLYCOL) DIMETHACRYLATE

The cationic part of the charge carrier transport was investigated for gel electrolyte films prepared by photoinitiated polymerization of ol igo(ethylene glycol) dimethacrylate (EG)(n)DMA in the presence of a pl asticizer and LiCF3SO3. Methyl group terminated oligo(ethylene glycol) s (EG)(n)DME and those with polar endgroups and different n were used to study the influence of the polarity and the chain length of the pla sticizer on the cationic transference number. t(+) was determined by t he steady state current technique and was calculated from the charge c arrier self diffusion coefficients measured by Li-7 and F-19-PFG-NMR w ith well agreeing results. Endcapping of plasticizers by polar groups enhances t(+) due to an improved charge carrier separation which is di scussed as deviation from the Nernst-Einstein equation. In gel electro lytes t(+) was found to depend on the ability of the plasticizer to co ordinate cations in competition with the polymer. Therefore, relativel y high t(+) values (t(+) > 0.3) were observed for gel electrolytes con taining higher molecular oligo(ethylene glycol)s as plasticizer or a r educed content of ethylene glycol units in the polymer network. The in teractions between charge carriers and plasticizers in the liquid elec trolyte systems have been characterized by the Stokes' radii of the pl asticizer and the charge carriers. (C) 1998 Published by Elsevier Scie nce Ltd. All rights reserved.