Phase behavior in quaternary ammonium ionic liquid-propanol solutions: Hydrophobicity, molecular conformations, and isomer effects

Molecular Assembling in Mixtures of Hydrophilic 1-Butyl-1-Methylpyrrolidinium Dicyanamide Ionic Liquid and Water

The infrared absorbance spectrum of the ionic liquid 1-butyl-1-methylpyrrolidinium dicyanamide, mixed with water at two different concentrations, was measured between 160 and 300 K in the mid infrared range. Both mixtures do not crystallize on cooling; however, remarkably, the one with an ionic liquid (IL):water composition of 1:3 displays a cold crystallization process on heating in a restricted temperature range between 240 and 250 K. A portion of the water participates to the cold crystallization. On the contrary, with an IL:water composition of 1:6.6 no crystallization takes place. Upon water addition the vibration frequencies of the anion and of some lines of the cation are blue shifted, while the absorption lines of water are red shifted. These facts are interpreted as the evidence of the occurrence of the hydrogen bonding of water, as the hydrogen bonding acceptor with respect to the anion (anion∙∙∙O-H bonds develop) and as hydrogen donor for the cation (C-H∙∙∙O bonds can form). Microscopic inhomogeneities in the samples and their evolution with temperature are discussed.

Lithium-triggered spontaneous formation of polyiodides in room-temperature ionic liquid-alcohol solutions

In this study, the effect of alcohol on polyiodide formation in room-temperature ionic liquid (RTIL) was examined by time evolutions of Raman spectra in the low-frequency region and by color changes of the sample. The RTIL was 1-methyl-3-propylimidazolium iodide, [C₃mim][I]. Polyiodides develop in [C₃mim][I]‑lithium salt-ethanol solutions (Abe et al., Chem. Phys. 502 (2018) 72.). Without the external addition of iodine or without an external electric field, the irreversible transformation from I^- to I₃^- indicates that charge unbalancing was promoted by lithium ion. Polyiodide formations were not induced by sodium or potassium ions. Strong alcohol effects were observed directly by the time-dependent Raman bands in the low-frequency region.

Reversible exchange of wetting state of a hydrophobic surface via phase change material coating

Reversible exchange of the wetting state of a hydrophobic surface is examined. Solution crystallization of a polycarbonate surface is carried out to form hierarchically distributed micro/nano size spherules and fibrils on the surface. Although the solution crystallized surface has hydrophobic characteristics, the contact angle hysteresis remains high. Functionalized silica particles are deposited on the crystallized polycarbonate surface to improve the droplet contact angle and lower contact angle hysteresis. The liquid film of n-octadecane with 1.5 μm thickness is formed on the functionalized silica particles deposited crystallized surface, which results in hydrophilic surface characteristics. The n-octadecane film solidifies upon reducing the temperature on the surface and solid flakes of n-octadecane are formed. This arrangement changes the surface wetting state to hydrophobic. Liquefaction and solidifying of the n-octadecane film at the functionalized silica deposited surface gives rise to reversible exchange of surface wetting state. This behavior is attributed to exposure of emerging functionalized silica particles to the free surface in the region of the solid n-octadecane flakes. The water droplet is cloaked by the liquid n-octadecane while forming a ridge around the droplet. In this case, the water droplet becomes mobile at the surface because flow develops in the n-octadecane liquid film at the onset of liquefaction.