Synthesis and ionic conductivity of mixed substituted polysiloxanes with oligoethyleneoxy and cyclic carbonate substituents

New comb polysiloxanes with mixed substituents were synthesized by hydrosilylation of PMHS with 4-allyloxymethyl-1,3]dioxolan-2-one and tri(ethylene glycol) allyl methyl ether (AMPEO₃). The effect of the incorporation of carbonate groups on ionic transport, viscosity and thermal properties has been investigated. When doped with lithium bis(trifluorosulfonyl) imide, LiTFSI, the mixed substituted polysiloxane polymers with varying carbonate content all exhibited conductivity higher than those for the polysiloxanes with pure carbonate or pure oligoethyleneoxy substituents. The maximum ambient conductivity in this series was 1.62× 10⁻⁴ S/cm, occurring for the polymer containing 8.5% polar carbonate groups at a doping level of EO/LiTFSI = 15. The impedance measurement results showed that polymers containing larger amounts of carbonate groups exhibited lower conductivity, probably because of their increased viscosity and higher glass transition temperature. The conduction mechanism for these new comb polymers obeys free volume theory, as indicated by conductivity data fit to the VTF equation. We dedicate this paper to Professor Dick Jones, polysilane pioneer and valued friend.