CO2 absorption and ion mobility are investigated in a series of 50/50 wt% aqueous solutions of choline-based ionic liquids with different cations and anions: [N1,1,4,2OH][Threo], [N1,1,5,2OH][Threo], [N1,1,6,2OH][Threo], [N1,1,5,2OH][β-ala] and [N1,1,5,2OH][Tau]. The process of CO2 absorption was completed in an hour reaching maximum of absorption capacity 0.07–0.10 wt% to ionic liquid (by 0.4–0.6 molar ratios). A rapid CO2 absorption is observed by the formation of solid product as a result of reaction between CO2 molecule and the ionic liquid. Diffusion coefficients of the cation and anion in the mixture are comparable while the diffusivity of water molecules is found to be quite different from the ions. In the process of CO2 absorption, an increase in the diffusivity of ions is observed due to the precipitation of solid products and depletion of ions contents in the liquid phase of the system. 13C NMR measurements of diffusivity of CO2 enriched with 13C isotope showed that a part of the absorbed CO2 remained in the liquid phase being physically and chemically bound to ions. The ionic liquid is re-cycled by evaporating water and releasing CO2 molecules using vacuum and temperature.

In this work, we compared the effects of curcumin and cholesterol directly competing to insert into the DMPC lipid bilayer during bilayer formation from an initially non-ordered state. 2H and 14N nuclear magnetic resonance spectroscopy showed that curcumin is not embedded deep in the lipid bilayer and interacts mainly with the head group of the lipid. In a more complex system of DMPC/CHOL/CUR, curcumin amplifies the effect of cholesterol on the ordering of lipid acyl chains.

Translational diffusion coefficients of ethoxylated isononylphenol molecules C9H19C6H4O(C2H4O)nH in carbon tetrachloride were measured by nuclear magnetic resonance diffusometry. The hydrodynamic radii of the molecules were determined within the framework of the Stokes–Einstein relation. We showed that ethoxylated isononylphenols in carbon tetrachloride do not form micelles, and the dependence of the diffusion coefficients and, accordingly, the hydrodynamic radii of the nonionic surfactants on the number of oxyethylene groups have a kink in the region n = 6–8.

Based on the 1H relaxation of transverse nuclear magnetization of triblock-copolymer Pluronic F-127 in D2O, we proposed a model of the associated pluronic structure in which the polyethylene oxide of molecules in neighboring micelles are intertwined in regions of overlapping micellar coronas, while the polypropylene oxide cores of the micelles play a role of nodes in the 3D network. 

1-Ethyl-3-methyl-imidazolium acetate ([EMIM][OAc]) is one of the most widely used ionic liquids for various applications. This study is focussed on the chemical stability of [EMIM][OAc] on the surfaces of polar glass plates. ¹H and ¹³C NMR spectroscopy and NMR diffusometry of [EMIM][OAc] IL confined between glass plates with a specific surface area 10⁵–10⁶ m⁻¹ are thoroughly investigated. A rapid and spontaneous reaction took place on the surfaces of glass plates leading to the formation of neutral chemical moieties as evident by the appearance of new signals in the ¹H NMR spectra. These new products are assigned as N-heterocyclic carbene (NHC) and acetic acid. These neutral chemical moieties have significantly increased the ion diffusivity by dissociation of the cation and the anion in [EMIM][OAc] IL. The yield and rate of formation of NHC and acetic acid are found to increase with the increasing surface area of polar glass plates and the time of contact between the IL and glass surfaces. Based on NMR spectroscopy, a dissociative reaction mechanism is proposed for the formation of free NHC in the neat [EMIM][OAc] IL.

CO2 absorption in a series of choline-based ionic liquids is investigated using solid-state 13C and 15N MAS NMR spectroscopy. Natural abundance and 13C enriched CO2 gas was purged through 50 wt% aqueous solutions of alkyldimethyl(2-hydroxyethyl)ammonium threonine, [N1,1,n,2OH][Threo], (alkyl = butyl, pentyl and hexyl) and pentyldimethyl(2-hydroxyethyl)ammonium taurine [N1,1,5,2OH][Tau]. The process of CO2 absorption results in precipitation of a solid sediment, which stays in equilibrium with the liquid phase. Upon degassing of the sample, the sediment is dissolved back into the IL-aqueous phase. Solid state 13C and 15N MAS NMR data suggest that the solid sediment is composed of neutral threonine (or taurine) in the zwitterionic forms and the liquid phase contained the products of reactions between the ionic liquids and CO2 molecules. A plausible mechanism for formation of the solid sediments and the reaction products in liquid phases is suggested.

Ethylammonium nitrate (EAN) ionic liquid confined between flat polar glass platesdemonstrates variable diffusivity that is sensitive to an external static magnetic field. Outside the magnetic field, diffusivity between the plates is higher than that in the bulk. However, after placing the system in a strong static magnetic field, the diffusivity gradually decreased. These processes occur during transformations between phases formed in EAN subjected to micrometer-size restrictions outside and within the magnetic field (Filippov et al., J. Mol. Liq. [2018] 268, 49). In this study, we used samples of two types: (i) with roughened surface formed by treatment of the glass plates with aqueous solutions of hydrofluoric acid and (ii) with vacuum deposited TiO₂ layers with a thickness of ca. 1 μm at glass-plate edges. Neither the surface modification of the glass plates, nor the TiO₂ layers controlled thickness of EAN confined between glass-plates significantly changed the above-described effects, which have been observed in studies using untreated glass plates. Therefore, the range of systems with detected phase transformations in EAN and accompanying effects, such as accelerated diffusivity and change in diffusivity under the influence of a static magnetic field, was expanded to the systems with roughened surfaces and the systems with TiO₂ layers controlled inter-plates distances. Results of experiments with roughened surfaces additionally suggested that the phase transformation of confined EAN in the external magnetic field is isotropic in nature rather than a phase transition from “layered to bulk” structures.

Diffusivity of crude oils confined in pores of sand decreased with raising the fraction of oil at ordinary temperatures. This behaviour is suggested to be caused by adsorption of the high-molecular fractions of oils at the solid–liquid interface.

We used 1H pulsed field gradient (PFG) NMR to study the self-diffusion of polyethylene glycol (PEG) with average molecular mass of 200 and ions in mixtures of PEG with imidazolium bis(mandelato)borate (BMB) and imidazolium bis(oxalato)borate (BOB) ionic liquids (ILs). The ionic liquid was mixed with PEG in the concentration range of 0–100 wt%. Within the temperature range of 295 to 353 K, the diffusion coefficient of BMB is slower than that of the imidazolium cation. The diffusion coefficients of PEG, as well as the imidazolium cation and BMB anions, differ under all experimental conditions tested. This demonstrates that the IL in the mixture is present in at least a partially dissociated state. Generally, increasing the concentration of PEG leads to an increase in the diffusion coefficients of PEG and both the ions, and decreases their activation energy for diffusion. NMR chemical shift alteration analysis showed that the presence of PEG changes the chemical shifts of both ions but in different directions. Impedance spectroscopy was used to measure the ionic conductivity of the ionic liquids mixed with PEG.

We used 1H NMR diffusometry to study mixtures of ethylammonium nitrate (EAN) with water (3.1–12.4 mol% of added H2O) confined between polar glass plates and exposed to a static magnetic field of 9.4 T. The presence of such restrictions reverses the concentration dependence of the diffusivities of the EA (ethylammonium) cation and water typical for the bulk system. The presence of water weakens the effects of a static magnetic field on diffusion of the EA cation as well as on proton exchange of –NH3 groups. Surprisingly, the amplitude of the echo signal of water protons decreases during exposure to the magnetic field and finally disappears, a phenomenon that depends on the concentration of water in the system. Based on experimental data, we suggest that water in the system is present in two states with different dynamic properties. One type of water formed in confinement possesses NMR relaxation time typical for liquids; its diffusivity can be measured by 1H NMR. The second type of water is formed upon exposure of the sample of the first type to the magnetic field and eventually includes all the water in the system. This type of water possesses “solid-like” NMR relaxation features that makes it “invisible” to the NMR diffusometry technique. We suggest that this second type of water is adsorbed onto the glass plates. Correspondingly, EAN exists in two liquid phases: the first one contains an EAN-water mixture, while the second one contains neat EAN, and forms on the microscopic scale range under the influence of a static magnetic field.