SYNTHESIS OF POLYSILOXANES BEARING CYCLIC CARBONATE SIDE-CHAINS - DIELECTRIC-PROPERTIES AND IONIC CONDUCTIVITIES OF LITHIUM TRIFLATE COMPLEXES

Polysiloxanes with cyclic carbonate side chains were prepared by hydrosilation of poly(hydromethylsiloxane) (PHMS) with vinyl-containing cyclic carbonates in acetonitrile using the divinyltetramethyldisiloxane platinum complex as the catalyst. This is initially a heterogeneous reaction since the PHMS is insoluble in acetonitrile, but the polymer eventually becomes soluble as the reaction proceeds. Under these conditions, no gelation due to competitive reactions with the carbonate is observed. The polymers are highly viscous liquids (T(g)'s of ca. -30-degrees-C) and have dielectric constants ranging from ca. 22 to 44, to our knowledge the largest for any silicones. These polymers can also dissolve large quantities of lithium triflate and represent new polymer electrolytes. The T(g)'s of the polymer/salt complexes having one Li+ per 10 cyclic carbonates are ca. -20-degrees-C, accounting in part for the relatively low conductivity of ca. 5 x 10(-7) S/cm at 25-degrees-C. Diluents such as acetonitrile can afford substantial increases in conductivity.