Molecular relaxation and ionic conductivity of ionic liquids confined in apoly(vinylidenefluoride) polymer matrix: Influence of anion and cation type

Abstract

Blends of poly(vinylidenefluoride) (PVDF) and ionic liquids (ILs) with different cations and anions have beenprepared by solvent casting. The IL content was the same in all blends of the series. Molecular relaxation andionic conductivity have been systematically studied by broadband dielectric relaxation spectroscopy (BDS) inwide frequency (0.1 Hz–1 MHz) and temperature ranges (−120 to 150 °C) and the results have been analysed interms of dielectric modulus M*(ω) and conductivityσ*(ω) formalisms. The main relaxation process (β-relaxa-tion) of the amorphous phase of the blend that integrates amorphous polymer chain segments and IL moleculeswas observed. Significant differences in the Vogel-Fulcher-Tammann (VFT)fitting parameters in the PVDF/ILblends with different anions were detected. The conductivityσ*(ω) formalism shows that it is strongly depen-dent on the miscibility of the IL with the amorphous PVDF chains and the type of anion. The Barton-Namikawa-Nakajima (BNN) relationσ0∼ωcis fulfilled for all PVDF/IL blends except for that containing 1-ethyl-3- me-thylimidazolium hydrogen sulfate, [Emim][HSO4]. The activation energy of theacconductivity, calculatedaccording to the Dyre model, decreases for all PVDF/IL blends with respect to neat PVDF. The structure of thecation of the IL has been found to exert less influence on the dielectric and conductivity properties of the blends.