IONIC-CONDUCTIVITY IN ORGANIC-SOLIDS DERIVED FROM AMORPHOUS MACROMOLECULES

By use of principles derived from the study of the effect of copolymerization on crystallinity and lamellae thickness in semicrystalline systems, amorphous polymers of ethylene oxide have been synthesized. It has been shown that the ionic conductivity in the presence of lithium triflate at room temperatures is significantly improved in these completely amorphous materials, provided the comonomer used has the same C:O ratio as polyethylene oxide). The optimum conductivity at 25 °C achieved was on the order of 2 X 10-5 Ω-1 cm-1 compared to 5 X 10-8 Ω-1 cm-1 for semicrystalline PEO. The mechanical properties were, however, poor. Amorphous terpolymers were synthesized with the same composition but containing 5% of cross-linkable sites. The effect of cross-linking was to reduce the conductivity by an order of magnitude. However, mechanical properties were good. Studies of a model system dimethoxyethane with propylene carbonate showed that conductivities on the order of 10-2 Ω-1 cm-1 were possible in organic media with lithium triflate. Extension of this concept to the amorphous cross-linked PEO systems showed that the addition of 50% propylene carbonate gave a flexible film with good mechanical properties and a conductivity of 10-3 Ω-1 cm-1 the design of eletrochemical cells is discussed. © 1990, American Chemical Society. All rights reserved.