Water Structure Breaker Research Articles

Toward an understanding of volumetric and isentropic compressibility behavior of imidazolium-based ionic liquids in aqueous polymer solutions

ABSTRACT A systematic experimental density and sound velocity measurement was carried out for imidazolium-based ionic liquids (ILs) in pure water and in aqueous solutions of 0.03 w/w of water-miscible polymers with different structures and molar masses at T= (288.15, 293.15, 298.15, 303.15 and 308.15) K and p = 84.5 kPa. The ILs under investigation are 1-butyl-3-methylimidazolium hydrogen sulphate ([C4mim][HSO4]) and 1-butyl-3-methylimidazolium bromide ([C4mim]Br). The effects of temperature, polymer type, and IL anion type on the various volumetric and compressibility properties, such as apparent molar volume, isentropic compressibility, apparent molar isentropic compressibility, and infinite dilution apparent molar properties for transfer of ILs from water to aqueous polymer solution were scrutinised. From the gathered results, ion-water interactions, ion-ion interactions at finite concentration, and water-structure breaking character for aqueous solutions of [C4mim][HSO4] are more considerable than aqueous solutions of [C4mim]Br. However, [C4mim]Br-polymer interactions are more favourable than interactions between [C4mim][HSO4] and the studied polymers.

PH-dependent interactions of biologically important metal ions with hen egg white lysozyme based on its hydration properties: Thermodynamic and mechanistic insights

Importance of metal ion selectivity in biomolecules and their key role in proteins are widely explored. However, understanding the thermodynamics of how hydrated metal ions alter the protein hydration and their conformation is also important. In this study, the interaction of some biologically important Ca2+, Mn2+, Co2+, Cu2+, and Zn2+ ions with hen egg white lysozyme at pH 2.1, 3.0, 4.5 and 7.4 has been investigated. Intrinsic fluorescence studies have been employed for metal ion-induced protein conformational changes analysis. Thermostability based on protein hydration has been investigated using differential scanning calorimetry (DSC). Thermodynamic parameters emphasizing on metal ion-protein binding mechanistic insights have been well discussed using isothermal titration calorimetry (ITC). Overall, these experiments have reported that their interactions are pH-dependent and entropically driven. This research also reports the strongly hydrated metal ions as water structure breaker unlike osmolytes based on DSC studies. These experimental results have highlighted higher concentrations of different metal ions effect on the protein hydration and thermostability which might be helpful in understanding their interactions in aqueous solutions.

Self-assembling of surface active drug amitriptyline hydrochloride in association with additives: Role of surface activity in the pharmaceutical applications

The self-assembling of surface active antidepressant drug amitriptyline hydrochloride (AMT) has been studied to determine the micellar solution behavior in the presence of polar (methanol and ethanol), dipolar aprotic solvents (acetone and 1,4 dioxane), salt (NaCl) and water structure-breakers (urea) at 298 K using surface tension and electrical conductivity measurements. The counterion binding parameter and the ionization degree of AMT micelles have been determined by electrical conductivity measurements. To better analyze the influences of additives on micellar behavior of AMT, surface features of AMT were defined using Gibbs Adsorption Isotherm in water and in association with various amounts of additives conducted by surface tension measurements. Both conductometric and surface tension experiments were also used to detect the critical micelle concentration (CMC) of AMT. The experimental results indicated that CMCs of AMT were influenced in the presence of additives. Self-aggregation of AMT was totally inhibited when methanol, ethanol, acetone, 1,4 dioxane, and urea concentration is attained to a certain value while the CMC of AMT reduced with the increase in concentration of NaCl.

Chaotropic Anion-Based "Water-in-Salt" Electrolytes for Beyond Li-Ion Energy Storage Systems

Electrochemical energy storage systems (EESS) with high energy density, safety, low cost, and low carbon footprint have become indispensable in the modern era of ubiquitous electronics, electric vehicles, and grid storage. Current EESS lack these characteristics due to the utilization of critical materials that are precious, flammable, difficult to recycle, and pose a threat to the environment. Whereas aqueous electrolytes offer higher safety and lower cost. Nevertheless, their biggest bottleneck is the narrow electrochemical stability window (ESW) that is preventing them from attaining higher energy and power densities in most of the aqueous EESS. For instance, multivalent metal-ion-based aqueous rechargeable batteries promise high energy density due to the multivalent redox chemistry of metal ions (Al3+, Zn2+, etc.) but they exhibit much lower energy density in real experiments due to the limited ESW of the aqueous electrolytes. The water-in-salt (WIS) electrolytes can potentially eliminate this barrier by offering a larger ESW. However, an anion’s nature, i.e., kosmotropic (water structure-maker) or chaotropic (water structure breaker) plays an important role in the expansion of the ESW in WiS-electrolytes. In general, the kosmotropic anions have a negative impact on the ESW by disturbing the solvation shell of the counter cations. On the other hand, chaotropic anions increase the ESW by limiting the fraction of free water in the electrolytes by pushing water molecules into the solvation shells of the cations.We demonstrate WIS-electrolytes of metal-perchlorates (metal: Al, Zn, etc.) containing strong chaotropic anion (ClO4 -). As a result, the WiS-electrolytes of Zn- and Al-perchlorates demonstrate expanded ESW of 2.80 V and 4 V, respectively. The electrochemical tests of the electrolytes are performed using carbon-based redox-active electrode materials. We employ the new electrochemical systems in aqueous rechargeable multivalent dual-ion batteries, revealing superior performance to standard aqueous electrolytes. Our findings provide new possibilities for widening the ESW and enhancing the energy and power density in aqueous EESS, especially for grid storage applications. A. Zafar, G. Abbas, K. Knizek, M. Silhavik, P. Kumar, P. Jiricek, J. Houdkova, O. Frank, J. Cervenka, Journal of Materials Chemistry A, 2022, 10, 2064-2074.A. Zafar, G. Abbas, M. Silhavik, K. Knizek, O. Kaman, F. J. Sonia, P. Kumar, P. Jiricek, J. Houdková, O. Frank, J. Cervenka, Electrochimica Acta, 2022 404, 139754.

A comparative photophysical study of molecular association of structurally similar phenothiazine dyes in aqueous solutions of caffeine

This paper comparatively reports the role of a molecular additive (caffeine) on the absorption and emission spectral characteristics and molecular association of a series of phenothiazine dyes in aqueous solutions. The studied dyes were five phenothiazine dyes (thionine, azure A, azure B, toluidine blue O, and methylene blue) with strong close molecular structures. The spectral data of the water-caffeine-dye systems were systematically analyzed and discussed based on the chemical structure of the constituent molecules. The aggregate structure and the dimer characteristics were analysed based on the exciton model. The additive was to act as strong water structure-breaker over the range of studied concentration. The main driving force for breaking the dye aggregation is water-caffeine or dye-caffeine interactions at low and moderate caffeine contain. At the high additive concentrations, the caffeine-caffeine, dye-dimer caffeine, and caffeine-water-caffeine might have crucial role in the spectral and aggregation behavior of the dyes. Caffeine induces markedly fluorescence quenching in emission spectra of the studied dyes.

Mechanism of dye solubilization and de-aggregation by urea

Urea is an effective solubilizer for dyes with low aqueous solubility. To establish, at a molecular level, the reason behind the action of urea as an effective solubilizer, we employ a rigorous statistical thermodynamics approach based on the Kirkwood-Buff theory of solutions. We show that (i) contrary to the classical hypothesis on “water structure breaking”, the effect of urea on dye hydration makes a minor contribution to solubilization; (ii) the driving force of solubilization is the accumulation of urea around hydrophobic dye molecules.

Thermodynamic analysis of cellulose complex in NaOH–urea solution using reference interaction site model

Thermodynamic analysis of the empirical data for the solvation of cellulose in aqueous NaOH/urea solution was performed in this study; this was achieved by employing the three-dimensional Reference Interaction Site Model theory coupled with the Kovalenko–Hirata closure approximation. The preferential distributions of Na+, OH−, urea, and water that were in a close proximity to the cellulose molecule, enabled the calculation of the solvation energy and the contribution of each solvent species to the solvation energy. By dividing the solvation energy into the solvent potential energy under the consideration of the solvent–solute interaction and the solvent reorganization energy, cellulose solvation in the NaOH/urea solution was observed to be primarily due to reorganization of the water molecules around the cellulose molecule. The solvated structure was suggested to be composed of cellulose as an inclusion in helical clusters of Na+, OH−, urea, and water, wherein the clusters comprised a repeated arrangement of OH− hydrate, water molecules, urea hydrate, and water molecules. Cellulose is suspected to play the role of a water structure maker in the presence of NaOH and urea, and as a water structure breaker in the absence of NaOH and/or urea.

Borate Species, Volumetric and Transport Properties of Aqueous Lithium Metaborate Solution from 288.15 to 318.15 K

The present work reports acidity (pH), Ranman spectrum, densities (ρ) and viscosity (η) of aqueous lithium metaborate solution at different temperatures. Polyborate distributions in aqueous LiB(OH)4 solution were calculated using measured pH values and literature equilibrium constants. Combining Raman spectra and polyborate distributions result, the polyborate species were ascertained in solution. The apparent molar volumes (Φv), standard molar volumes ($$\Phi _{v}^{0}$$), apparent molar expansibilities ($$\Phi _{E}^{0}$$), and coefficient of thermal expansion (α) in aqueous lithium metaborate solution have been calculated from the density data. The viscosity data have been analyzed by Jones–Dole equation. Different thermodynamic parameters have been used to explore solute–solute, solute–solvent interactions and effect of concentration and temperature. All the parameters calculated from density and viscosity indicate that the lithium metaborate is water structure breaker.

Measurement and correlation of thermophysical properties in aqueous solutions of some novel bio-based deep eutectic solvents (lactic acid/amino acids) at T = (298.15 to 313.15) K

Thermodynamic properties of novel bio-based deep eutectic solvents (DESs) and their mixture with other solvents is of great importance in extraction and pharmaceutical sciences. In the present study new class of these neoteric sustainable solvents composed of amino acids and lactic acid have been prepared, density and speed of sound data for neat lactic acid/alanine, lactic acid/glycine and lactic acid/histidine and their aqueous mixture have been measured over the entire composition range at T = (298.15, 303.15, 308.15 and 313.15) K. Based on these data, some of the thermodynamic properties including the excess molar volumes (VE), apparent molar volume (Vϕ), excess isobaric thermal expansion (αp,mE), the excess molar isentropic compressibility (κEs,m) and limiting apparent molar expansibility (ϕE,10) have been calculated. For all of the studied systems above, these important properties have been analysed based on various solute-solvent interactions, occurring between the components of the mixtures. Furthermore, it has been found that all the investigated DESs act as a structure-breaker in water over the whole temperature range using Hepler’s constant. The properties have been correlated by the Redlich-Kister type equations.

Effect of gelatin protein on self-association behavior of sodium salt of ibuprofen drug in urea solution

Herein, multi-techniques approaches such as conductometry, tensiometry, fluorometry, and FT-IR were engaged to evaluate the interaction between sodium salt of ibuprofen (IB) and gelatin (GN) at 298.15 K in 250 mmol·kg−1 urea (UR) solution. The current employed drug is used for relief of pain. The employed IB drug interacts through GN protein like the interaction between surfactants and polymers. It is clear that the graph obtained from the conductometric and tensiometry methods shows two clear breaks. Urea acts as water structure breaker and their presence in solution enhance in surface charge of aggregates occurs. The obtained first break spot is labeled critical aggregation concentration (cc) which is quit beneath the usual critical micelle concentration (cmc) besides this the subsequently break spot denotes second one is regarded as polymer saturation point (pp) and this akin to cmc. The interaction between IB and GN in UR solution increases as concentration of protein increases in the solution mixtures as clear from their obtained cc value because the value of cc reduces through enhancing the concentration of GN (%w/v), in spite of this the value of pp value increases with increase in concentration of GN means more drug needed for complete saturation of binding site of protein. In UR solution, the Gibbs free energy of micellization (ΔGmic) for singular IB was achieved negative exploring that micellization process is spontaneous in nature. The other different evaluated thermodynamic parameters such as free energy of aggregation (ΔGagg), free energy of transfer (ΔGt), etc. were found in favor of interaction between IB and GN. Fluorometry technique was utilized to find out the various parameters such as micropolarity, aggregation numbers (Nagg), etc. to verify the interaction amongst studied constituents and with the interaction between them were also assessed by FT-IR study.

Mixed Micellar and Interfacial Studies of Triblock Copolymers with Amphiphilic Drug Ibuprofen in Aqueous Urea Solutions

AbstractMixed micellar and surface properties of non‐ionic triblock copolymers (Pluronic® P123 and F68) and non‐steroidal anti‐inflammatory drug Ibuprofen (IBF) have been evaluated in aqueous urea (100 mM) solutions with the help of surface tension and fluorescence measurements at 298.15 K. Various bulk and surface parameters such as critical micelle concentration (CMC) of the mixtures, micellar mole fraction (X), interaction parameter (β) and free energies were calculated using Clint, Rubingh, Rosen and Maeda models. In aqueous solutions, all the mixtures show synergistic interactions and are more in mixtures of IBF with P123. These interactions decrease in presence aqueous urea solution due to breaking of water structure surrounding the hydrophobic moieties by urea molecules resulting in delayed mixed micellization. Micellar aggregation number (Nagg) obtained from the steady state fluorescence quenching indicate that the participation of triblock copolymer is more than the drug IBF in mixed micelle formation. Stern‐Volmer constant (KSV), dielectric constant (Dexp), and micropolarity (I1/I3) have also been evaluated and their contribution in the mixed micellar systems have been discussed.

Aqueous Mixtures of Urea and Trimethylamine-N-oxide: Evidence for Kosmotropic or Chaotropic Behavior?

Trimethylamine-N-oxide (TMAO) and urea are commonly produced in many extremophilic microorganisms that live in harsh environments. In view of high temperature, high pressure, or high salt content, TMAO is known as a protein structure stabilizer, whereas urea destabilizes protein structures even under ambient conditions. Despite clear evidence, destabilizers are often regarded as chaotropes, meaning water-structure breakers, whereas kosmotropes as water-structure makers are classified as stabilizers. Using atomistic molecular dynamics simulations, we study aqueous mixtures of TMAO and urea in various biologically relevant concentrations to gain insight into the molecular details of their mutual cross-interactions and their influence on water dynamics and structure. Our results for binary and ternary solutions in combination with different mixing ratios show that both co-solutes strengthen the water network in terms of dynamic and structural aspects. Slight differences in the water binding behavior between both species result in only negligible compensation effects. The outcomes of our simulations thus question the validity and the ill-considered use of attributes like kosmotropic or chaotropic substances for stabilizers and destabilizers.

Molecular Interactions of Pyridoxine Hydrochloride in Aqueous Mixed Solutions of D-Glucose, D-Fructose, and D-Lactose at Different Temperatures

Density and ultrasonic velocity values for solutions of pyridoxine hydrochloride in aqueous mixed solutions containing D-glucose, D-fructose, and D-lactose have been obtained for various concentrations and at temperatures 298.15–313.15 K. Volumetric and acoustic parameters such as partial molar volumes, partial molar adiabatic compressibilities, partial molar expansibilities were determined using density and ultrasonic velocity data. The analysis of the obtained data has been done by using Masson’s equation and interpretation was done in terms of solute–solute and solute–solvent interactions. The pyridoxine hydrochloride acts as a structure breaker in water as well as in binary aqueous mixed solutions of D-glucose, D‑fructose, and D-lactose.

Tuning the Phase Transition from UCST-Type to LCST-Type by Composition Variation of Polymethacrylamide Polymers.

Polymethacrylamide copolymers with hydrophobic N-substituted acrylamides, such as N-cyclohexylacrylamide and N-tert-butylacrylamide, are rare examples of polymers showing composition-dependent thermoresponsive behavior in water. They show unexpected behavior different from the conventional copolymers of a thermoresponsive polymer with hydrophobic comonomers. On increasing the amount of the hydrophobic comonomer in the polymer, there is a change from UCST-type phase behavior to complete solubility, followed by compositions showing LCST-type transition and insolubility in water (U-S-L-I-type change). At 50 mol% of less hydrophobic N-tert-butyl acrylamide (logP 0.87) in contrast to ≈25 mol% of N-cyclohexylacrylamide (logP 1.51), the broad UCST-type transition of polymethacrylamide is turned to LCST-type transitions with very narrow hysteresis in water and PBS buffer. The use of H-bond and water-structure breaker showed the role of H-bonding and hydrophobic interactions in phase transitions of UCST-type and LCST-type, respectively. This work is an important add-on to the infant field of nonionic polymers of UCST-type.

Densities and Apparent Molar Volumes of Aqueous Solutions of K4Fe(CN)6, K3Fe(CN)6, K3Co(CN)6, K2Ni(CN)4, and KAg(CN)2 at 293 to 343 K

Densities of aqueous solutions of K4Fe(CN)6, K3Fe(CN)6, K3Co(CN)6, K2Ni(CN)4, and KAg(CN)2 have been measured with a vibrating-tube densimeter at temperatures from 293.15 to 343.15 at 5 K intervals over the approximate concentration range 0.02 to 0.4 mol·kg–1. Apparent molar volumes, Vϕ, calculated from these data were fitted with an extended form of the Redlich–Rosenfeld–Meyer equation to obtain the standard partial molar quantities, V°. The Vϕ and V° values for all the salts are in reasonable agreement with literature data at all temperatures. Deviations of the Vϕ values from the Debye–Huckel limiting law were found to increase considerably with increasing anion charge. Values of V° for the cyanometallate anions were obtained using an appropriate extrathermodynamic assumption and were found to increase with increasing crystallographic size or ionic charge except for Fe(CN)64–, which shows a remarkable contraction of more than 35 cm3·mol–1 relative to Fe(CN)63–. The origins of this anomaly are unclear. Isobaric expansivities, α, of all the salt solutions show the greatest increase with solute concentration, but the smallest dependence on the nature of the anion, at lower temperatures. These effects are consistent with the dissolved ions changing from water-structure breaking to net structure making with increasing temperature.

Born-Oppenheimer Molecular Dynamics Simulations of a Bromate Ion in Water Reveal Its Dual Kosmotropic and Chaotropic Behavior.

The solvation structure and dynamics of a bromate (BrO3-) ion in water are studied by means of Born-Oppenheimer molecular dynamics simulations at two different temperatures using the Becke-Lee-Yang-Parr functional with Grimme D3 dispersion corrections. The bromate ion possesses a pyramidal structure, and it has two types of solvation sites, namely, the bromine and oxygen atoms. We have looked at different radial and orientational distributions of water molecules around the bromate ion and also investigated their hydrogen bonding properties. The solvation structure of the bromate ion is also compared with that of the iodate (IO3-) ion, which is structurally rather similar to the bromate ion and was found to have some unusual solvation properties in water. It is found that the bromate ion follows a similar trend as that followed by the iodate ion as far as the solvation structure is concerned. However, the effect of the former on surrounding water is found to be much weaker than that of the latter. On the dynamical side, we have looked at diffusion, residence dynamics, and also the orientational and hydrogen bond relaxation of water molecules around the BrO3- ion and compared them with those of the bulk. Dynamical results are presented for both H2O and D2O around the BrO3- ion. Interpretation of the dynamical results in terms of structure-making (kosmotropic)/-breaking (chaotropic) properties of the BrO3- ion reveals that the bromine atom of this ion acts as a water structure breaker, whereas the three oxygens act as water structure makers. Thus, in spite of being a single ion, the bromate ion has dual characteristics and the experimentally observed kosmotropic ability of this ion is actually a trade-off between a chaotropic site (the bromine atom) and three kosmotropic sites (three oxygen atoms) that are present in the ion.

Properties of L-ascorbic acid in water and binary aqueous mixtures of D-glucose and D-fructose at different temperatures

Using density and sound velocity partial molar volumes, partial molar adiabatic compressibilities, partial molar expansibilities and structure of L-ascorbic acid have been determined in water and aqueous mixtures of D-glucose and D-fructose at different concentrations and temperatures. Masson’s equation was used to analyze the measured data. The obtained parameters have been interpreted in terms of solute–solute and solute–solvent interactions. It is found that the L-ascorbic acid acts as structure breaker in water as well in binary studied mixtures.

Taurine as a water structure breaker and protein stabilizer

The enhancing effect on the water structure has been confirmed for most of the osmolytes exhibiting both stabilizing and destabilizing properties in regard to proteins. The presented work concerns osmolytes, which should be classified as “structure breaking” solutes: taurine and N,N,N-trimethyltaurine (TMT). Here, we combine FTIR spectroscopy, DSC calorimetry and DFT calculations to gain an insight into the interactions between osmolytes and two proteins: lysozyme and ubiquitin. Despite high structural similarity, both osmolytes exert different influence on protein stability: taurine is a stabilizer, TMT is a denaturant. We show also that taurine amino group interacts directly with the side chains of proteins, whereas TMT does not interact with proteins at all. Although two solutes weaken on average the structure of the surrounding water, their hydration spheres are different. Taurine is surrounded by two populations of water molecules: bonded with weak H-bonds around sulfonate group, and strongly bonded around amino group. The strong hydrogen-bonded network of water molecules around the amino group of taurine further improves properties of enhanced protein hydration sphere and stabilizes the native protein form. Direct interactions of this group with surface side chains provide a proper orientation of taurine and prevents the {text{SO}}_{3}^{ - } group from negative influence. The weakened {text{SO}}_{3}^{ - } hydration sphere of TMT breaks up the hydrogen-bonded network of water around the protein and destabilizes it. However, TMT at low concentration stabilize both proteins to a small extent. This effect can be attributed to an actual osmophobic effect which is overcome if the concentration increases.

Additive-induced aggregate changes of two structurally similar dyes in aqueous solutions: A comparative photophysical study

Absorption and emission spectral characteristics of the two structurally similar phenothiazine dyes, azure B and toluidine blue, in aqueous solutions of the two sets of molecular additives (ureas and monosaccharides) were studied as a function of the dye and additive concentrations. The absorption spectra of the dyes were also studied in pure tetramethylurea with an aprotic nature. The spectral data were analyzed using DECOM Program. The dimer structure of the interacting molecules in these dyes was discussed using the exciton model. The urea class of additives was found to act as water structure-breakers over the range of studied concentration. The carbohydrate additives were found to act as water structure-breakers at low concentrations. However, the water structure breaking process may be disfavored by the additive-additive interactions at higher concentrations. It can be concluded that at low additive concentrations, the main driving force for breaking the dye association is water-additive interaction, which disrupts the water hydrogen bonds induced by the additives. However, at the high additive concentrations, the different phenomena including additive-additive and additive-dye interactions can change the structure, strength, and aggregative properties of the dyes. Finally, the urea in water induces noticeably fluorescence quenching in emission spectra of both the dyes.

Dual-stimulus-responsive crosslinking chitosan as a gene vector

Absorption and emission spectral characteristics of the two structurally similar phenothiazine dyes, azure B and toluidine blue, in aqueous solutions of the two sets of molecular additives (ureas and monosaccharides) were studied as a function of the dye and additive concentrations. The absorption spectra of the dyes were also studied in pure tetramethylurea with an aprotic nature. The spectral data were analyzed using DECOM Program. The dimer structure of the interacting molecules in these dyes was discussed using the exciton model. The urea class of additives was found to act as water structure-breakers over the range of studied concentration. The carbohydrate additives were found to act as water structure-breakers at low concentrations. However, the water structure breaking process may be disfavored by the additive-additive interactions at higher concentrations. It can be concluded that at low additive concentrations, the main driving force for breaking the dye association is water-additive interaction, which disrupts the water hydrogen bonds induced by the additives. However, at the high additive concentrations, the different phenomena including additive-additive and additive-dye interactions can change the structure, strength, and aggregative properties of the dyes. Finally, the urea in water induces noticeably fluorescence quenching in emission spectra of both the dyes.