Multinuclear (1H, 31P, and 7Li) NMR was applied to understand the ion dynamics in silica-based iongels with a fluorine-free ionic liquid (IL), tetrabutylphosphonium 2-2-(2-methoxyethoxy)ethoxy acetate, [P4,4,4,4][MEEA], doped with 10 and 30 mol % of LiMEEA. The results were compared with bulk [P4,4,4,4][MEEA]/LiMEEA electrolytes and those confined in the “hard” silica matrix of a porous glass. It was found that lithium ion (Li+) local dynamics and Li+ diffusion coefficients are strongly affected by confinements in an iongel and in the porous glass, as was revealed from the analysis of NMR parameters, such as diffusion decays (DDs) in 7Li PFG NMR spectra, broadening of the 7Li NMR resonance lines and variations in the 31P and 7Li chemical shifts. However, NMR diffusometry data does suggest that the studied electrolytes in the iongel confinement yet have properties like bulk electrolytes: (i) high ion diffusivities, (ii) weak alterations of Vogel-Fulcher-Tammann (VFT) parameters for diffusion; and (iii) high transport numbers of ions. The diffusion coefficients of the [MEEA]- anion and the [P4,4,4,4]+ cation are comparable in the bulk, while they are significantly different in the iongels: The specific interactions of the [P4,4,4,4]+ cations with the negatively charged silica matrix slowed down diffusivities of the cations, while almost no effect of the matrix on diffusivities of the [MEEA]- anions was noticed. It was also found that the tortuosity of the iongel channels has a negligible effect on diffusivities of ions. The lithium complexation or/and solvation shells of Li+ ions remained unaffected. Thus, the ionic liquid-based iongel electrolyte acquired the advantages of a semi-solid phase and offered transport properties of a liquid electrolyte. 

The reaction of wood with maleic anhydride (MA) and sodium hypophosphite (SHP) has been identified as a viable modification method, with macroscopical properties indicating formation of cross-linking to explain the results. However, the chemical reaction between wood and the modification reagents has not been studied yet. To resolve this, the reaction was studied with solid-state 13C cross-polarization magic-angle-spinning (CP-MAS) and 31P MAS nuclear magnetic resonance (NMR) and X-ray photoelectron spectroscopy (XPS) to reveal the formation of bonds between wood components, MA and SHP during the treatments to explain the formation of cross-linking and the possible fixation of phosphorus in wood. XPS, solid state 13C and 31P MAS NMR revealed the maleation of wood in the absence of SHP, whilst its presence led to forming a succinic adduct observed through the C-P bond formation, as evidenced by the loss of the maleate C=C bonds at around 130 ppm and the upfield shift of the peak at 165–175 ppm, which was also significantly smoothed, as well as the increase in a peak at 26 ppm due to the reaction between the maleate group and SHP; however, the C-P-C bond could not be unambiguously rationalized from the obtained data. On the other hand, a resonance line at 16 ppm in 31P MAS NMR and the peaks in the XPS P 2p spectrum suggested the formation of a cross-linked structure at low concentrations of SHP, which was more likely to be phosphonate (C-P-O) than organophosphinic acid (C-P-C). The results herein provide a greater fundamental understanding of the mechanisms involved in the reaction of wood, MA and SHP, providing further scope for improved treatment systems in the future.

In this work, we investigate the ion pair tetramethylphosphonium cation, [P1,1,1,1]+, and bis(oxalato)borate anion, [BOB]−, as a model system for the study of ionic liquids interacting with both hydroxylated and oxygen terminated α-SiO2 (001) surfaces, using first-principles electronic structure theory. We use a single ionic pair and clusters of ion pairs, in order to have exclusively neutral supercell slab models. We use dispersion-corrected density functional theory (DFT) to ascertain that both the strong physical binding between the ions, dominated by ionic binding, and the weaker physical binding of ions to the different surfaces are correctly described. We have found that the binding of ion pairs is stronger to the hydroxylated α-SiO2 (001) surface compared to the oxygen terminated surface, which is attributed to the formation of H-binding with the oxygen atom(s) of the [BOB]− anion. Through rotation of ionic pair(s), we estimate the surface-ions energy barrier for translational movement and, thus, the strength of H-binding of the ions. At the surface of hydroxylated α-SiO2 (001), we have studied how water molecules form a network of H-binding with the OH groups of the surface and the [BOB]− anion, which offers an explanation for the reduction in the friction of ionic liquids on the inclusion of water. We suggest modeling protocols for simulation of ion pairs on surfaces, which can open up the possibility to use DFT to aid in designing and understanding the physicochemical mechanism of interactions of ionic materials (including ionic liquids) in various technological applications.

A series of orthoborate-based ionic materials of bis(glycolato)borate ([BGB]) and bis(ethylene-1,2-dioxy)borate anions ([BEDB]) coupled with tetrabutylphosphonium ([P4444]) and tetrabutylammonium ([N4444]) cations have been synthesized, and their physicochemical properties are characterized. The ionic materials based on the most popular orthoborate anion, bis(oxalato)borate anion ([BOB]), which contains four carbonyl groups, are all liquid at ambient temperature, while the bis(glycolato)borate ([BGB]) anion, with two carbonyl groups, and the bis(ethylene-1,2-dioxy)borate ([BEDB]) anion, without carbonyl groups, render solids at ambient temperature. The ionic materials based on the [BGB] anion display the highest decomposition temperatures, and those based on the BEDB anion are the lowest. The [P4444][BGB], [P4444][BEDB], and [N4444][BEDB] salts feature significantly wider plastic phase I temperature ranges than their analogues. FTIR spectroscopy, multinuclear (15N, 31P, 13C, and 11B) solid-state NMR spectroscopy, and single-crystal X-ray diffraction were all used to unveil the ionic interactions and structural features, which display weaker ionic interactions for [BEDB] compared to [BGB] when bearing the same cation and present relatively higher crystallinity of [P4444][BGB] among the ionic materials.

This review paper presents the results of a study conducted using nuclear magnetic resonance (NMR) methods to investigate the dynamic behaviour of ionic liquid-based compositions in micrometre-spaced confinement. Ethylammonium nitrate (EAN) and other ionic liquid (IL) systems with nitrate anion in glass or quartz spaced confinement demonstrate anomalous cation dynamics that differ from those observed in bulk and in nano-confinement. It was demonstrated that the principal axis of the nitrate anion exhibits preferential orientation to the surface, akin to that in liquid crystals. It was shown that the cation translational mobility reversibly changes during exposure to a static magnetic field. This phenomenon was interpreted as a result of intermolecular structure transformations occurring in the confined ILs. The mechanisms of these transformations were discussed.

In this study, Kraft lignin was modified by ammonium dihydrogen phosphate (ADP) and urea for achieving phosphorylation and carbamylation, aiming to protect wood against biological and fire attack. Scots pine (Pinus sylvestris L.) sapwood was impregnated with a water solution containing Kraft lignin, ADP, and urea, followed by heat treatment at 150 °C, resulting in changes in the properties of the Kraft lignin as well as the wood matrix. Infrared spectroscopy, 13C cross-polarisation magic-angle-spinning (MAS) nuclear magnetic resonance (NMR), and direct excitation single-pulse 31P MAS NMR analyses suggested the grafting reaction of phosphate and carbamylate groups onto the hydroxyl groups of Kraft lignin. Scanning electron microscopy with energy dispersive X-ray spectroscopy indicated that the condensed Kraft lignin filled the lumen as well as partially penetrating the wood cell wall. The modified Kraft lignin imparted fire-retardancy and increased char residue to the wood at elevated temperature, as confirmed by limiting oxygen index, microscale combustion calorimetry, and thermogravimetric analysis. The modified wood exhibited superior resistance against mold and decay fungi attack under laboratory conditions. The modified wood had a similar modulus of elasticity to the unmodified wood, while experiencing a reduction in the modulus of rupture.

Self-diffusion in a bitumen emulsion was studied by H-1 NMR. The emulsion forms two phases: continuous and dispersed. The continuous aqueous phase contains mainly water, with the energy of activation of the diffusion process equal to that of bulk water, while its diffusivity is smaller than that of bulk water by a factor of 2. The dispersed phase consists of bitumen droplets containing confined water, whose dynamics is characterized by a fully restricted diffusion regime in cavities with sizes of similar to 0.11 mu m. Therefore, the studied bitumen emulsion can be described by a model of a complex multiple emulsion of the water/oil/water (WOW) type. The suggested model does agree well with data from H-1 NMR spectroscopy and diffusometry of the bitumen emulsion doped with paramagnetic MnSO4(aq) as well as with an additional H-1 NMR study of the emulsion structure, in which emulsion stability was compromised by freezing at 253 K.

The exterior application of fire-retardant (FR) timber necessitates it to have high durability because of the possibility to be exposed to rainfall. In this study, water-leaching resistance of FR wood has been imparted by grafting phosphate and carbamate groups of the water-soluble FR additives ammonium dihydrogen phosphate (ADP)/urea onto the hydroxyl groups of wood polymers via vacuum-pressure impregnation, followed by drying/heating in hot air. A darker and more reddish wood surface was observed after the modification. Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, solid-state 13C cross-polarization magic-angle-spinning nuclear magnetic resonance (13C CP-MAS NMR), and direct-excitation 31P MAS NMR suggested the formation of C–O–P covalent bonds and urethane chemical bridges. Scanning electron microscopy/energy-dispersive X-ray spectrometry suggested the diffusion of ADP/urea into the cell wall. The gas evolution analyzed by thermogravimetric analysis coupled with quadrupole mass spectrometry revealed a potential grafting reaction mechanism starting with the thermal decomposition of urea. Thermal behavior showed that the FR-modified wood lowered the main decomposition temperature and promoted the formation of char residues at elevated temperatures. The FR activity was preserved even after an extensive water-leaching test, confirmed by the limiting oxygen index (LOI) and cone calorimetry. The reduction of fire hazards was achieved through the increase of the LOI to above 80%, reduction of 30% of the peak heat release rate (pHRR2), reduction of smoke production, and a longer ignition time. The modulus of elasticity of FR-modified wood increased by 40% without significantly decreasing the modulus of rupture.

A series of 19 ionic liquids (ILs) based on phosphonium and imidazolium cations of varying alkyl-chain lengths with the orthoborate anions bis(oxalato)borate [BOB]−, bis(mandelato)borate, [BMB]− and bis(salicylato)borate, [BScB]−, are synthesized and studied using small-angle neutron scattering (SANS). All measured systems display nanostructuring, with 1-methyl-3-n-alkyl imidazolium-orthoborates forming clearly bicontinuous L3 spongelike phases when the alkyl chains are longer than C6 (hexyl). L3 phases are fitted using the Teubner and Strey model, and diffusely-nanostructured systems are primarily fitted using the Ornstein-Zernicke correlation length model. Strongly-nanostructured systems have a strong dependence on the cation, with molecular architecture variation explored to determine the driving forces for self-assembly. The ability to form well-defined complex phases is effectively extinguished in several ways: methylation of the most acidic imidazolium ring proton, replacing the imidazolium 3-methyl group with a longer hydrocarbon chain, substitution of [BOB]− by [BMB]−, or exchanging the imidazolium for phosphonium systems, irrespective of phosphonium architecture. The results suggest there is only a small window of opportunity, in terms of molecular amphiphilicity and cation:anion volume matching, for the formation of stable extensive bicontinuous domains in pure bulk orthoborate-based ILs. Particularly important for self-assembly processes appear to be the ability to form H-bonding networks, which offer additional versatility in imidazolium systems.

Some aprotic and protic ionic liquids (ILs) containing nitrate anion demonstrate unusual dynamic behavior of cations when these ILs are enclosed in micrometer-spaced layers between glass plates. We applied 17O and 15N NMR spectroscopy to discover the state and transformations of 17O and 15N isotopically enriched nitrate anion of ethylammonium nitrate (EAN) enclosed between glass plates. 15N NMR spectra demonstrated preferential orientation of the principal axes of the nitrate anions perpendicular to the normal of the glass surface. Therefore, isotropic ionic liquid EAN, when placed within a micrometer-spaced enclosure, forms an ordered phase, which is similar to a liquid crystal. The peculiarity of this phase is that the cations do not have a predominant orientation. Other features of this phase that are typical for liquid crystal phases are the changed local and translational dynamics in comparison with the isotropic state and slow transformation occurring under the action of an external magnetic field.