Gel electrolytes were prepared by photopolymerization of oligo(ethylen
e glycol)(23) dimethacrylate ((EG)(23)DMA) in the presence of LiCF3SO3
and various oligo(ethylene glycol) derivatives as plasticizers. The i
nfluence of the chain length and the end groups, i.e. cyanoacetic este
rs, of the plasticizer on the charge carrier separation, the mobility
of the ions, the conductivity of the electrolyte system and the cation
ic transference number t(+) was studied. Using plasticizers endcapped
with polar groups, a distinct increase of the part of free ions compar
ed with that in nonpolar plasticizers was observed by Raman spectrosco
py. As a result of pulsed-field gradient NMR and electrochemical inves
tigations including transference number measurements, we have found a
strong correlation between plasticizer mobility and ion diffusion and
with that, ionic conductivity. t(+) measurements indicate a relationsh
ip between the ability of the plasticizer to interact with the cations
and the cationic part of charge transport.