HIGH-CONDUCTIVITY ELECTROLYTES COMPOSED OF POLYSTYRENE CARRYING PENDANT OLIGO(OXYETHYLENE)CYCLOTRIPHOSPHAZENES AND LICLO4

Ionic conductivities of the complexes of polystyrene with pendant penta[oligo(oxyethylene)]cyclotriphosphazenes (poly(SDEP), (-OCH2CH2)(n)OCH3, n = 2; poly(STEP), n = 3) with LiClO4 were investigated as a function of temperature and salt concentration. The glass transition temperatures (T(g)) of side chains of poly(SDEP) and poly(STEP) were observed at -62 and -67-degrees-C, respectively. Interestingly, the T(g) values of the poly(STEP)-Li salt complexes of [Li+]/O > 0.5 become higher than those of the poly(SDEP)-Li salt system. The conductivities of the complexes exhibit a non-Arrhenius temperature dependence, indicating an ion transport in the amorphous phase. In spite of the low segmental mobility of poly(STEP)-Li salt complexes, their conductivities are higher than those of the poly(SDEP) system and the maximum conductivities of 1.1 x 10(-4) S/cm at 60-degrees-C and 5.1 x 10(-4) S/cm at 100-degrees-C have been achieved at [Li+]/O = 0.05. The high conductivities might be explained by an ion transport through a continuous conducting phase consisting of a number of oxyethylene chains without being affected by the mobility of the backbone. This implies that the flexibility of backbone is not an important factor to achieve a high conductivity. From the correlation between the polymer characteristics and the conductivity, the conduction appears to occur at a rate governed by both the mobility of side chains and the stability of the complex, which relates with ion-dipole interactions.