Enhanced interfacial polarization and electro-responsive characteristic of di-ionic poly(ionic liquid)s

Poly(ionic liquid)s are providing potential platforms to develop new generation of water-free polyelectrolyte-based electorheological materials due to strong polarizability and intrinsic hydrophobicity. To enhance polarization and electro-response by employing combined contribution of ion number density and ion transport dynamic, we here have developed a kind of di-ionic poly(ionic liquid)s for use as new electorheological materials. It has found that di-ionic poly(ionic liquid)s have enhanced electorheological effect compared with common mono-ionic poly(ionic liquid)s but enhancement degree depends on counterion type. The enhancement of di-ionic poly(ionic liquid)s with PF₆ ⁻ as counterions is more significant than those with TFSI⁻ as counterions. By combining dielectric spectra with Raman and X-ray scattering analyses, it has demonstrated that enhanced electorheological effect of di-ionic poly(ionic liquid)s is because di-ionic structure can increase interfacial polarization by combined contribution of enhanced ion number density and transport dynamic. However, the enhancement degree is more significant for PF₆ ⁻ than TFSI⁻ due to its small size and low plasticizing capacity.