IONIC INTERACTIONS IN POLYMERIC ELECTROLYTES BASED ON LOW-MOLECULAR-WEIGHT POLY(ETHYLENE GLYCOL)S

It is shown that ionic conductivity of polymeric electrolytes based on low molecular weight amorphous polyglycols can be modified by the add ition of alpha-Al2O3 fillers containing surface groups of the Lewis ac id type. An enhancement of conductivity over pure PEG-LiClO4 electroly te is observed for PEG-alpha-Al2O3-LiClO4 composite electrolytes conta ining from 0.5 to 3 mol/kg of the lithium salt. This increase in condu ctivity is coupled with the lowering of the viscosity of composite ele ctrolytes and increasing chain flexibility when compared to the PEG-Li ClO4 system as shown by rheological and DSC experiments. A decrease in the fraction of ionic aggregates is also seen from the FT-LR experime nts for composite electrolyte in this salt concentration range. FT-IR studies of the C-O-C stretching mode has shown reduction in the transi ent cross-link density obtained after the addition of alpha-Al2O3 in t he salt concentration range corresponding to the conductivity enhancem ent. The phenomena observed are explained in view of ion-ion and ion-p olymer interactions, involving dispersed filler particles, which are o f the Lewis acid-base origin.