Attempts at lithium single-ionic conduction by anchoring sulfonate anions as terminating groups of oligo(oxyethylene) side chains in comb-type polyphosphazenes

Abstract

Novel comb-type polyphosphazenes with anchored lithium sulfopropyl oligo(oxyethylene) side chains [SEP] were synthesized by a one-step reaction with lithium bisulfite and polyphosphazenes containing oligo(oxyethylene) side chains terminated with allyl groups [AEP]. The dc ionic conductivity ([sigma]) of SEP was measured using lithium electrodes and compared with hybrid (polymer-salt complexes) between LiSO[sub 3]CF[sub 3] and the corresponding non-sulfonate comb-type polymer [MEP], i.e., poly(bis[[omega]-methoxyoligo(oxyethylene)]phosphazene). While the time dependence of [sigma]/[sigma][sub o] ([sigma][sub o]: initial conductivity) of SEP showed a constant value, that of the hybrid system drastically decreased with time due to the self-polarization by mobile anions. The stationary values of [sigma] after prolonged electrolysis were 7.1 x 10[sup [minus]8] S cm[sup [minus]1] for SEP and 8.5 x 10[sup [minus]7] S cm[sup [minus]1] for the hybrid at 1.0-V dc supply. 16 refs., 2 figs., 2 tabs.