Tuning the glass transition of siloxane-based poly(ionic liquid)s towards high ion conductivity

Herein, we report a simple and versatile synthetic approach towards siloxane-based poly(ionic liquid)s (PILs) with unusually low glass transition temperatures (T-g) down to -73 degrees C, and thus liquid-like behavior at room temperature. We designed a polydimethylsiloxane-derived copolymer carrying dialkylimidazolium moieties, and by careful selection of the side-chain length and the type of anions we were able to manipulate its Tg over a wide range and reach high ionic conductivities (sigma(DC)) up to 4.8 x 10(-5) S/cm at 300 K. The ionized species make up only a minor fraction (<25 mol%) of the overall repeating units and are supposedly randomly distributed: Yet our results indicate dramatic effects on the thermal properties due to repulsive interactions between ionic and non-ionic segments.

Automated summary

A synthetic approach towards siloxane-based poly(ionic liquid)s with low T-g and high ionic conductivity was reported. The Tg could be manipulated by adjusting side chain length and anion type to achieve high ionic conductivity. The ionized species only make up a minor fraction of the repeating units, but have significant effects on thermal properties.