The physicochemical properties of the deep eutectic solvents with triethanolamine as a major component

Abstract

Different deep eutectic solvents (DESs) of triethanolamine (TEOA) and oxalic acid (OA), glacial acetic acid (AA), L-(+)-lactic acid (LA), oleic acid (OLA), glycerol (G), ethylene glycol (EG), propylene glycol (PEG), choline chloride (ChCl) or 1,3-dimethylurea (DMU) were prepared and characterized re-garding their physicochemical (density, viscosity, electrical conductivity, refract-tive index, coefficient of volume expansion, molecular volume, lattice energy, and heat capacity) properties over the temperature range of 293.15-363.15 K at 101.325 kPa. For all tested DESs, the density, viscosity and refractive index decreased with increasing the temperature while the electrical conductivity increased. Those temperature dependence for viscosity and electrical conducti-vity are described by the Vogel-Tamman-Fulcher equations. The viscosity and molar conductivity, which exhibited a linear behavior, were correlated by the fractional Walden rule. Besides, the Fourier transform infrared spectroscopy (FTIR) was used to study the functional groups of these DESs while thermogra-vimetric analysis (TGA) and differential scanning calorimetry (DSC) provided the information about their stability. The tested DESs of TEOA possess desirable properties for use in various industrial processes, such as extractions, separations, chemical technology and biotechnology. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. III 45001, Grant no. 451-03-68/2020-14/200133]

Competition-Induced Macroscopic Superlubricity of Ionic Liquid Analogues by Hydroxyl Ligands Revealed by in Situ Raman

“…Different component ratios (i.e., 1:2, 1:5, 1:10, and 1:20, denoted as ILA 1:2 , ILA 1:5 , ILA 1:10 , and ILA 1:20 , respectively) of solid ChCl and TEOA were mixed by stirring and heating to form a homogeneous colorless liquid (Figure a). Raman spectra revealed that the components’ characteristic peaks of C–N (at ∼724 cm –1 ) and C–H (at 2800–3100 cm –1 ) in ChCl and C–O (at 800–960 cm –1 and ∼1050 cm –1 ) and O–H (at 3100–3600 cm –1 ) in TEOA coexist in ILA 1:2 , ILA 1:5 , ILA 1:10 , and ILA 1:20 (Figure b), demonstrating the formation of ILAs due to the weak interactions between H-bond donors and H-bond acceptors, such as O–H···O, O–H···Cl, and O–H···N, as well as the additional Coulombic action between ions . The corresponding Raman spectra focusing on the part of H-bonding interactions are magnified in Figure c; in contrast to the predominantly strong H-bonding interactions in ChCl, the H-bonding interactions in TEOA can be divided into the three components of strong (at ∼3255 cm –1 ), weak (at ∼3382 cm –1 ), and non-H-bonds (at ∼3478 cm –1 ) .…”

“…The viscosity of ILAs was measured with a rheometer (DHR-1, TA). Their morphologies and element contents were analyzed by scanning electron microscopy (SEM, FEI Scios 2 HiVac, 31 The corresponding Raman spectra focusing on the part of H-bonding interactions are magnified in Figure 1c; in contrast to the predominantly strong H-bonding interactions in ChCl, the H-bonding interactions in TEOA can be divided into the three components of strong (at ∼3255 cm −1 ), weak (at ∼3382 cm −1 ), and non-H-bonds (at ∼3478 cm −1 ). 27 The H-bonding interactions of ILA 1:2 , ILA 1:5 , ILA 1:10 , and ILA 1:20 mainly consist of strong and weak H-bond components.…”

Density and viscosity of deep eutectic solvents at different temperatures and compositions: Measurement and prediction model

“…This has become a topic of great interest for researchers in various fields utilizing DESs. 13,14 Previous studies on DES properties have mainly focused on the effect of temperature, 16,17 with only a few reports considering the effect of chemical structure and component proportion. [18][19][20] Several computational modeling methods have been developed in recent years for predicting the density and viscosity of DESs.…”