Excess Properties, Computational Chemistry, and Spectral Analysis of [Diethanolamine + Alcohols (Ethanol, n‑Propanol, or n‑Butanol)] Ion-Like Liquids

Density (ρ) and viscosity (η) values of [diethanolamine (DEA) + alcohols (ethanol, n-propanol, or n-butanol)] ion-like liquids were measured at T = 298.15–318.15 K and atmospheric pressure. Based on these data, the excess molar volume (V m E), viscosity deviation (Δη), activation Gibbs free energy (ΔG*), excess activation Gibbs free energy of viscous flow (ΔG *E), apparent molar volume (V φ), partial molar volume (V̅), and thermal expansion coefficient (αp) of ion-like liquids were calculated. At the same time, the variation of density with various compositions and temperatures was evaluated by the Jouyban–Acree model and nonlinear least squares method. The dependence of viscosity and dynamic viscosity on composition was fitted by the Grunberg–Nissan, Eyring–Margules, Heric, and McAllister equations, and the dependence of viscosity on temperature was fitted by the Arrhenius equation. Meanwhile, the V m E, Δη, and ΔG *E of ion-like liquids were fitted by the Redlich–Kister (R–K) equation. The intermolecular hydrogen bond (IHB) was discussed in depth on the basis of the change of ultraviolet (UV) and Raman spectra. To further prove the IHBs and their interaction forms, the monomolecular and bimolecular stable structures of DEA with alcohols were optimized by density functional theory (DFT), and the weak interactions between molecules were discussed in depth.