AN ION CONDUCTED TOUR THROUGH SOME POLYMER ELECTROLYTES

The development of both dry polymer electrolytes and gel or inert-supp ort polymer electrolytes is discussed and their performances compared. Conductivities have been measured for comb-branch polymers, with cati on-binding side-chains, as a function of temperature and in nearly eve ry case the response was non-Arrhenius. This can be explained by recog nizing that ion transport in dry polymer matrices is a function of the flexibility of the polymer chains at the temperature of measurement. Ways to maximize this by attempting to lower the glass transition temp erature of the polymer/salt mixtures and improve the ionization of the salt, are described. The active participation of the polymer chain in ion transport can be modified by moving to externally plasticized sys tems, gels, or inert polymer supports. Two such examples are described , beta-cyclodextrin/ dimethylacetamide/salt gels and highly porous pol yethylene support films loaded with electrolyte. These show a reduced dependence of conductivity to) with change in temperature (T) which is a desirable feature in device manufacture, and an Arrhenius (log sigm a-1/T) behaviour. While these systems have several attractive features and they have been designed to minimize solvent leakage, there is no guarantee that leakage will not occur over a period of time and this l imitation must be recognized. (C) 1998 Society of Chemical Industry.