CRYPTAND ADDITION TO POLYELECTROLYTES - A MEANS OF CONDUCTIVITY ENHANCEMENT AND A PROBE OF IONIC INTERACTIONS

As a means of probing ionic interactions in and enhancing the conducti vity of single-ion conducting polymer electrolytes, the effect of the cryptand 6,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]hexacosane (crypt[2.2 .2]) on the conductivity of the sodium salt of oxypoly(oxyethylene)]pr opyl}methylsiloxane}-block- i-tert-butyl-4-hydroxyphenyl)butyl]methyls iloxane} (1) was studied. Both samples with and without cryptand displ ay the characteristic VTF temperature dependence of their conductiviti es (sigma = AT(-1/2) exp[-B/(T - T-o)]). The addition of crypt[2.2.2] results in a 15-fold increase in conductivity, independent of temperat ure and concentration. The glass transitions of the materials are unch anged upon cryptand addition, even at high ion concentrations where th e glass transition is dependent on ion content. Both the materials wit h and without crypt[2,2.2] exhibit a conductivity maximum with concent ration at [Na]/[ethylene oxide] = 2% (1.4 x 10(-6) S/cm neat and 1.7 x 10(-5) S/cm with crypt[2.2.2] at room temperature). A model based on equilibrium expressions for free-carrier formation is shown to be more appropriate than one based on an activated process because the former more closely describes the temperature-independent effect of crypt[2. 2.2] on the conductivity.