Influence of structural variations on electrical conductivity and solubility of 1-vinyl-3-alkylimidazole halogen ionic liquids

Abstract

Several 1-vinyl-3-alkylimidazolium halogens [VRIM]X, which are functional materials with ethylenic bonds, were synthesized using the microwave-assisted synthesis method. Fourier transform infrared spectroscopy and 1H nuclear magnetic resonance spectroscopy were carried out to analyze the resultant structures. The electrochemical properties and solubility of [VRIM]Br were investigated and discussed in detail. The temperature dependence of pure [VRIM]Br over a wide temperature range of 298.15–323.15 K fitted the Arrhenius equation well. At certain low concentrations, the electrical conductivity of the [VRIM]Br solution significantly increased with increasing solution concentration. The electrical conductivities of the [VRIM]Br observed in water, methanol, and ethanol showed the trend σ _water > σ _methanol > σ _ethanol. Conductometry showed that the critical micelle concentrations of the bromines in water, methanol, and ethanol were 6.8–6.9 × 10⁻⁶, 1.4–1.5 × 10⁻⁵, and 1.9–2.0×10⁻⁵ mol·L⁻¹, respectively; these results indicate that [VRIM]Br is an excellent surfactant. The solubility of [VRIM]X in common solvents was determined at 293.15 K, and results indicated that a decrease in solubility could be observed with decreasing dielectric constant of the solvent, elongation of the alkyl chain of the cation, and increasing anion size. Solubility parameters were also determined according to the Hildebrand-Scoff equation.

Keywords

1-vinyl-3-alkylimidazole halogen / ionic liquids / solubility / electrical conductivity / critical micelle concentration

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