Behavior Of Aqueous Solutions Research Articles

A semi-empirical model of radiolytic gas bubble formation and evolution during criticality excursions in uranyl nitrate solutions for nuclear criticality safety assessment

A novel mathematical and computational model for the formation and evolution of radiolytic gas in aqueous fissile solutions is presented. The model predicts the rate at which bubbles are formed and/or removed from the system using semi-empirical correlations calibrated by means of numerical simulation. The model is able to reliably predict the behaviour of aqueous fissile solutions, including transient effects due to the formation and removal of radiolytic gas. A further extension to the model enables its application to boiling systems.

On the important transition of sugar-based surfactant as a microreactor for C-S coupling in water: From micelle to vesicle

A reversible, temperature-induced micelle-to-vesicle transition of a sugar-based pseudogemini surfactant (C11D12) was employed for copper-catalyzed C-S coupling in water. The phase behavior and morphology of the C11D12 aqueous solution were investigated by DLS and cryo-TEM. The aggregates undergo a series of transitions upon increasing the temperature: spherical micelles were initially transformed into large vesicles, but they eventually transformed into smaller vesicles. The vesicular catalytic protocol accommodates an excellent substrate scope with moderate to high yields. The mechanisms of temperature-induced aggregate transition and vesicular catalysis were elucidated by experimental results and DFT calculations. It was revealed that the charge layer of the vesicle grants stronger nucleophilicity to the PhSO2-Cu-D12Ga intermediate. Furthermore, the aqueous reaction medium can be recycled and reused several times after easily separating the precipitated product.

Radionuclide 106Ru behavior in aqueous solutions by ion exchange, ultrafiltration, and centrifugation methods

The paper presents the results of 106Ru radionuclide behavior regularities study in aqueous solutions in a wide pH range by ultrafiltration, ion exchange and centrifugation methods. The regions of 106Ru various species existence in solution have been established: cationic 106Ru species at pH < 3.5; the transition region of non-ionic species formation in the range of pH 3.5–4.2 and the region of non-ionic species predominant formation at pH > 4.2. A characteristic feature of the studied solutions is the formation of non-ionic particles by microconcentrations of 106Ru via pseudocolloids at lower pH values as compared to ruthenium solutions with a concentration of 10-6–10-4 mol/dm3. The established regularities of the behavior of ruthenium radionuclides can be utilized to increase the efficiency of ion exchange and membrane separation methods at nuclear and radiation facilities for technological solutions and liquid radioactive waste treatment.

Microstructure of Ni-based hard facing alloy and its polarization behavior in aqueous solution with different pH and chloride concentration

To clarify the corrosion behavior of Ni-based hard facing alloy Colmonoy 56 and the preferential dissolution detail at the micrometer scale, the microstructure and the elemental distribution of a rod were analyzed, followed with the polarization measurement in aqueous solution with different pH and NaCl concentrations. This rod has Fe-, Si-, and Cr-solutioned [Ni] matrix with heterogeneously dispersed secondary phases of Cr23C6, CrB, Cr2B, and Cr5B3. The polarization curve largely changed with different pH: active in acid solution and passive in neutral and alkaline solution. The strongest passivation appeared at pH=11. Cl− promoted the corrosion attack to the [Ni] matrix. In the case of pH=11, Cl− caused the fast climb of anodic current from passivation at a less noble potential. Preferential dissolution of the [Ni] matrix occurred in most solutions, except in the case of pH=14 without NaCl, in which the secondary phases preferably dissolved.

Studies on synthesis, volume and conductivity behaviors of three novel pharmaceutical salts [CnPy][AceSA] (n = 8, 10, 12)

In the present work, three new pharmaceutical salts based on N-alkyl-pyridinium ([CnPy]+, n = 8, 10, 12) as the cations and acetyl-sulfacetamide ([AceSA]-) as an anion were synthesized. The thermal stability was measured by synchronous thermal analyzer. The solvation and micellization behaviors in aqueous solution were investigated by experimental density and conductivity data at different temperatures. These data were used to calculate the apparent molar volume at infinite dilution, V2,φ0, the apparent molar expansibility at infinite dilution, Eφ0, limiting molar conductivity, Ʌ0, critical micelle concentration, cmc, and the relative thermodynamic functions for the micellization of [CnPy][AceSA] in aqueous solution. The effect of the aliphatic chain length of N-alkyl-pyridinium cation and temperature on the estimated properties was examined. The obtained results confirmed that [CnPy]+(n = 8, 10, 12) cations with longer alkyl chain exhibit higher decomposition temperature, large V2,φ0, low cmc and Ʌ0 values. The results were discussed in terms of solute–solvent interactions and structural changes of [CnPy][AceSA] in water.

Conformation, Self-Organization and Thermoresponsibility of Polymethacrylate Molecular Brushes with Oligo(ethylene glycol)-block-oligo(propylene glycol) Side Chains.

Polymethacrylic molecular brushes with oligo(ethylene glycol)-block-oligo(propylene glycol) side chains were investigated by static and dynamic light scattering and viscometry. The solvents used were acetonitrile, tetrahydrofuran, chloroform, and water. The grafted copolymers were molecularly dispersed and dissolved in tetrahydrofuran and acetonitrile. In these solvents, the molar masses of copolymers were determined. In thermodynamically good solvents, namely tetrahydrofuran and acetonitrile, investigated copolymers have a high intramolecular density and the shape of their molecules resembles a star-shaped macromolecule. In chloroform and water, the micelle-like aggregates were formed. Critical micelle concentrations decreased with the lengthening of the hydrophobic block. Molecular brushes demonstrated thermosensitive behavior in aqueous solutions. The phase separation temperatures reduced with an increase in the content of the oligo(propylene glycol) block.

Aqueous solution thickening of amino acid‐based surfactant by alkylpyrrolidone

AbstractThe thickening behaviors in aqueous solution of mixed surfactant mixtures containing an amino acid‐based surfactant, sodium lauroyl sarcosinate (SLSar), and a nonionic surfactant, N‐dodecylpyrrolidone (C12P) were investigated using the rheological methods of steady‐shear and frequency sweep. The results varying the added C12P concentration and the mass ratio of SLSar and C12P indicate that the addition of C12P can promote the formation of wormlike micelles and hydrogels, resulting in viscosity enhancement in the mixed aqueous solution of SLSar and C12P. Viscosity maxima in SLSar/water/C12P systems are sensitive to pH, temperature, the concentration of added C12P, and the mass ratio of SLSar and C12P. In the high concentration of total surfactant (30–39 wt%), the enhancement of viscosity obviously occurs by adding 6 wt% C12P, whereas in the low concentration of total surfactant (15 wt%), the C12P must be added more than 9 wt% in 15 wt% mixtures of SLSar and C12P. Moreover, during the solution pH lowered from SLSar' natural pH of 7.2 to the mixture's pKa 5.2, the intermolecular forces between SLSar acid, SLSar anionic salt, and C12P gradually reduce the overall headgroups areas and contribute to the formation of wormlike micelles, hydrogels, and the thickening behaviors.

Reactive Amphiphilic Aprotic Ionic Liquids Based on Functionalized Oligomeric Silsesquioxanes

Abstract This paper discusses a method for the synthesis of ionic liquids which are mixtures of oligomeric silsesquioxanes (OSS) of polyhedral structure and their analogs with open chains containing aprotic cationic ionic groups with different lengths of alkyl substituents and reactive hydroxyl groups in the organic shell (OSS-ILs). This method includes the quaternization reaction of OSS with tertiary amine and primary and secondary hydroxyl groups by n-bromopropane or n-bromodecane. Obtained compounds were amorphous with glass transition temperature below 0 °C. The ionic conductivity of OSS-ILs increases with decreasing the alkyl substituent length and reaches 1.4·10−3 S/cm at 120 °C. Dynamic light scattering reveals that the length of alkyl substituent of OSS-ILs affects the assembly behavior in aqueous solutions. According to atomic force microscopy images, the surface morphology of the film of OSS-IL with short substituents showed disk-like flat micelles with an average diameter of 229 ± 92 nm and height of 2 nm. OSS-IL with long substituents formed polydisperse micellar morphologies, of which a majority showed elongated, worm-like structures with an average height of 2 nm. The ability to endow ionic conductivity and to tune morphology makes these materials promising as potential polymer electrolytes for various electrochemical applications, in particular ionic sensors and energy storage devices.

Features of Solution Behavior of Polymer Stars with Arms of Poly-2-alkyl-2-oxazolines Copolymers Grafted to the Upper Rim of Calix[8]arene.

Star-shaped polymers with arms of block and gradient copolymers of 2-ethyl- and 2-isopropyl-2-oxazolines grafted to the upper rim of calix[8]arene were synthesized by the “grafting from” method. The ratio of 2-ethyl- and 2-isopropyl-2-oxazoline units was 1:1. Molar masses and hydrodynamic characteristics were measured using molecular hydrodynamics and optics methods in 2-nitropropane. The arms of the synthesized stars were short and the star-shaped macromolecules were characterized by compact dimensions and heightened intramolecular density. The influence of the arm structure on the conformation of star molecules was not observed. At low temperatures, the aqueous solutions of the studied stars were not molecular dispersed but individual molecules prevailed. One phase transition was detected for all solutions. The phase separation temperatures decreased with a growth of the content of more hydrophobic 2-isopropyl-2-oxazoline units. It was shown that the way of arms grafting to the calix[8]arene core affects the behavior of aqueous solutions of star-shaped poly-2-alkyl-2-oxazoline copolymers. In the case of upper rim functionalization, the shape of calix[8]arene resembles a plate. Accordingly, the core is less shielded from the solvent and the phase separation temperatures are lower than those for star-shaped poly-2-alkyl-2-oxazolines with lower rim functionalization of the calix[8]arene.

Onset of Entanglement in Aqueous Solutions of Pullulan with Narrow Molar Mass Distributions

Dynamic viscoelastic behaviors were examined for aqueous solutions of pullulan samples, which are natural polysaccharides with weight-average molar masses (Mw) of 220, 390, and 820 kg mol–1 and narrow molar mass distributions such as Mw/Mn ≤ 1.1, over a concentration range from 5.0 to 467 g L–1 and a temperature range from 1 to 30 °C. The obtained viscoelastic data at different temperatures were superposed to compose master curves for storage and loss moduli (G′ and G″) using the time–temperature superposition principle. The Arrhenius-type temperature dependencies of the shift factors necessary to compose G′ and G″ master curves provided the activation energies (Ev*) of the viscoelastic relaxation times as functions of the concentrations (c) for each pullulan sample. Fundamental viscoelastic parameters such as the average relaxation time (τw), the steady-state compliance (Je), and the zero-shear viscosity (η0) were determined as functions of c for each pullulan sample. Above the critical concentrations (cen ∝ Mw–1) demonstrating the onset of entanglement formation among pullulan molecules, the characteristic relationships, Je–1 ∝ c2, τw ∝ cα–2Mw3.5, and η0 ∝ cαMw3.5 with α = 6.0, were obtained. Although this α value was substantially greater than that for usual synthetic polymers like poly(styrene) dissolved in good solvents where α ∼ 4.5, the Mw exponent of 3.5 for τw and η0 was identical to that of synthetic polymers. The Ev* value was close to the activation energy of the solvent, water viscosity of 19 kJ mol–1, in the dilute regime and abruptly increased with increasing c. Finally, Ev* approached a constant value of ca. 39 kJ mol–1 corresponding to the activation energy necessary for pullulan molecules to release entanglements above cen irrespective of the Mw values. The observed characteristic viscoelastic behaviors of aqueous pullulan solutions are reasonably interpreted by a theoretical model for associating polymers dissolved in good solvents.

A Unique Nano‐Capsule Possessing Inner Thermo‐Responsive Surface Prepared from a Toothbrush‐Like Comb−Coil Block Copolymer

AbstractPoly(N‐isopropylacrylamide) (PNIPAM) having lower critical solution temperature (LCST) behavior in aqueous solutions has been actively studied for various applications in nanotechnology and controlled drug delivery. In this work, a comb‐coil block copolymer is synthesized with PNIPAM coil and polyethyleneimine brushes. Self‐organization of the copolymer into micelle by heating and subsequent cross‐linking of the part of PEI corona resulted in a unique nanocapsule (i‐CLM) with hydrophilic cross‐linked PEI outer shell and thermo‐responsive PNIPAM inner brush. The nanocapsule appears as a vesicle‐like hollow at room temperature but did into micelle‐like spheres when heated. From dynamic light scattering measurement, it is revealed apparently that the nanocapsule exhibited well the swelling and the shrinking reversibly under heating and cooling and the feature is cycled repeatedly with gradual fashion under wide‐range of temperature responding. The carrier property of the nanocapsule is investigated by using hydrophobic fluorophore of Nile red (NR) as a probe and it is found that the hollow of the nanocapsule is a good nano pocket to promote the growth of nanocrystals of NR.

DNA‐organic molecular amphiphiles: Synthesis, self‐assembly, and hierarchical aggregates

AbstractWith the development of deoxyribonucleic acid (DNA) nanotechnology, various DNA nanostructures and DNA devices have been constructed, which exhibit potential applications in material science and biomedicine. Taking advantage of the programmability and biocompatibility of DNA, novel building block to chemically functionalize DNA with hydrophobic organic molecules has attracted more and more attention. Driving by amphiphilicity, DNA‐organic molecular amphiphiles have been demonstrated to self‐assemble or further induce hierarchically assemblies, providing novel‐specific properties. In this minireview, we summarize the recent progress of DNA organic molecular amphiphiles including their synthesis, self‐assembly behavior in aqueous solution, and the amphiphilic self‐assembly based on hierarchical DNA nano‐structures. We further briefly discuss the perspective of the application of the DNA‐organic molecular amphiphiles.

Improved Method for the Total Synthesis of Azaperone and Investigation of Its Electrochemical Behavior in Aqueous Solution

Improved Method for the Total Synthesis of Azaperone and Investigation of Its Electrochemical Behavior in Aqueous Solution

Single-Crystal Inorganic Helical Architectures Induced by Asymmetrical Defects in Sub-Nanometric Wires.

Constructing single-crystal inorganic helical structures is a fascinating subject for a large variety of research fields. However, the driving force of self-coiling, particularly in helical architectures, still remains a major challenge. Here, using MoO3-x sub-nanometric wires (SNWs) as an example, we identified that spontaneous helical architecture with different dimensional features is closely related with their surface asymmetrical defects. Specifically, the surface defects of SNWs are critical to produce the self-coiling process, thereby achieving the ordered helical conformations. Theoretical calculations further suggest that the formation of in-plane and out-of-plane coiling structures is determined by the asymmetrical distribution of the surface defects, and the inhomogeneous charge separation with strong Coulomb attraction dominates the different structural configurations. The resulting MoO3-x SNW exhibits excellent photothermal behaviors in both aqueous solutions and hydrogel matrixes. Our study provides a novel protocol to achieve helical structure design for their future applications.

Dielectric relaxation and molecular interactions study of saccharides in aqueous solutions

Time domain reflectometry (TDR) technique has been extensively used to study dielectric relaxation and solution properties of carbohydrates. Using TDR techninque, complex permittivity spectra of monosaccharides (d-fructose and d-xylose) and disaccharides (d-maltose monohydrates) were obtained in the frequency range of 10 MHz–50 GHz at various concentrations and temperatures. The static dielectric constant (ε0), dielectric constant at high frequency (ε∞), relaxation time (τ) and relaxation time distribution parameter (β) extracted from the complex permittivity spectra using least squares fit method. The values of static dielectric constant were also verified by LCR meter by dielectric measurement in the frequency range of 20Hz to 2 MHz at 25 °C. The relaxation behavior of aqueous solutions of monosaccharides and disaccharides has been illustrated by using Cole-Davidson model. Activation enthalpy (ΔH), entropy (ΔS) and Kirkwood correlation factor have been determined to study extent of hydrogen bonding. This data might be useful in pharmaceutical, food processing industry and in solubility prediction method in aqueous solution.

Sodium caseinate reduces the swelling of konjac flour: A further examination

Konjac flour can quickly swell and dissolve in a short time, leading to extremely high viscosity and easily agglomerative phenomenon. Such characters limit its application as ingredients in brewed foods and there is a high demand to restrict its swelling. Ethanol is usually adopted as a swelling inhibitor but it cannot be applied in the food industry. In this study, two types of milk (full-fat milk and low-fat milk) were selected and the swelling rates of konjac flour in these milk systems were measured. The results showed that the swelling rate of konjac flour significantly decreased. The konjac particles quickly cracked and dissolved in water within 3 min while only swelled in milk systems. To reveal which component in milk played a key role, we further studied the influence of the three components (lactose, whey protein isolate and sodium caseinate) on the swelling limitation of konjac flour. Sodium caseinate was found to be the strongest component than lactose and whey protein isolate in limiting the swelling of konjac flour. Our study revealed that casein was the crucial actor in inhibiting konjac flour swelling in milk and simulated milk system, indicating a new way to better control its swelling behavior in aqueous solution.

Thermophysical and taste behavior of sucrose in aqueous solution of some deep eutectic solvents at T= (288.15 to 318.15) K

Saccharide’s behavior in aqueous solutions has become a cornerstone of modern nutritional science, whether in academia or in industry. This study provides an exciting opportunity to advance our knowledge about taste quality by using thermophysical properties. So, the densities, speeds of sound, viscosities and refractive indices of sucrose in the aqueous solutions of choline chloride/urea, choline chloride/ethylene glycol, choline chloride/oxalic acid, dimethyl ammonium chloride/ethylene glycol as deep eutectic solvents (DESs) have been measured at T = (288.15–318.15) K and P = 86.6 kPa. Standard partial molar volumes, standard transfer volumes, and partial molar isentropic compressibility, have been calculated from the experimental data also, interaction volumes, and cavity volumes, have been computed from scaled particle theory. Taste quality data show that the studied DESs do not affect on the taste quality and sucrose falls in the sweet range and also, thermophysical properties suggest that solute-solvent interactions in choline chloride-ethylene glycol are stronger and strengthened with increasing the concentration of DESs and temperature.

Biophysical study on the phase transition behaviour of biocompatible thermoresponsive polymer influenced by tryptophan-based amino acid ionic liquids

Biocompatible thermoresponsive polymers are known to have numerous biomedical applications as they are capable of exhibiting a change in conformational states on changing the solution temperature. Poly(N-vinyl caprolactam) (PVCL) is one such polymer assessed frequently on conformational changes with biomolecules due to its amphiphilic nature. The goal of this work is to explore the impact of two tryptophan-based amino acid ionic liquids (AAILs), such as cholinium tryptophan ionic liquid ([CHO][Trp]IL) and tetraethylammonium tryptophan ionic liquid ([TEA][Trp]IL) on phase transition behaviour of aqueous PVCL solution. Biophysical techniques like steady-state fluorescence spectroscopy, thermal fluorescence spectroscopy, Fourier transform infrared (FTIR) spectroscopy, dynamic light scattering (DLS) and differential scanning calorimetry (DSC) are used to investigate the phase transition behaviour of aqueous PVCL-AAILs solution. The lower critical solution temperature (LCST) of PVCL was elevated by 4 and 2 °C on increase in the concentration from 1 to 5 mM of [CHO][Trp]IL and [TEA][Trp]IL, respectively. On comparing both AAILs, [CHO][Trp]IL has shown higher LCST (near to human physiological temperature) with aqueous PVCL solution than [TEA][Trp]IL due to its additional hydrogen bonding ability and its higher hydrophilicity compared to [TEA][Trp]IL. The structural functionalities of the cholinium cation like hydroxyl group and methyl substituents make it more advantageous than tetraethylammonium cation. This is the first time study on the phase transition behaviour of biocompatible thermoresponsive polymer PVCL influenced by tryptophan-based AAILs. These findings could be exploited for the development of biocompatible polymer to use in drug delivery and other biomedical applications.

Thermoresponsive Glycopolymers Based on Enzymatically Synthesized Oligo-β-Mannosyl Ethyl Methacrylates and N-Isopropylacrylamide.

We present here a series of thermoresponsive glycopolymers in the form of poly(N-isopropylacrylamide)-co-(2-[β-manno[oligo]syloxy] ethyl methacrylate)s. These copolymers were prepared from oligo-β-mannosyl ethyl methacrylates that were synthesized through enzymatic catalysis, and were subsequently investigated with respect to their aggregation and phase behavior in aqueous solution using a combination of 1H NMR spectroscopy, dynamic light scattering, cryogenic transmission electron microscopy (TEM), and small-angle X-ray scattering (SAXS). The thermoresponsive glycopolymers were prepared by conventional free radical copolymerization of different mixtures of 2-(β-manno[oligo]syloxy)ethyl methacrylates (with either one or two saccharide units) and N-isopropylacrylamide (NIPAm). The results showed that below the lower critical solution temperature (LCST) of poly(NIPAm), the glycopolymers readily aggregate into nanoscale structures, partly due to the presence of the saccharide moieties. Above the LCST of poly(NIPAm), the glycopolymers rearrange into a heterogeneous mixture of fractal and disc/globular aggregates. Cryo-TEM and SAXS data demonstrated that the presence of the pendant β-mannosyl moieties in the glycopolymers induces a gradual conformational change over a wide temperature range. Even though the onset of this transition is not different from the LCST of poly(NIPAm), the gradual conformational change offers a variation of the temperature-dependent properties in comparison to poly(NIPAm), which displays a sharp coil-to-globule transition. Importantly, the compacted form of the glycopolymers shows a larger colloidal stability compared to the unmodified poly(NIPAm). In addition, the thermoresponsiveness can be conveniently tuned by varying the sugar unit-length and the oligo-β-mannosyl ethyl methacrylate content.

Adsorption of Mercury(II) Ion in Aqueous Solution by Using Bentonite-Based Monolith

The removal of mercury from the waterbody remains a severe challenge in ensuring environmental safety due to its highly toxic and non-biodegradable properties. Adsorption is an evidently effective method for heavy metal removal in water. This research aims to study the mercury (II) ion adsorption behavior in aqueous solution onto extruded natural bentonite in monolithic structure, bentonite-based monolith (BBM) adsorbent. BBM was characterized by XRD, BET, and SEM, the results verify BBM could improve adsorption performance assumed on its structure. Adsorption efficiency, isotherm model, and adsorption kinetic were investigated. Experiments were performed in a lab-scale batch reactor with mercury solution concentration varied from 1 to 5 mg/L. The maximum adsorption efficiency discovered to be 63,9%. The experimental data fitted well to Langmuir isotherm (non-linear) and kinetic model pseudo first order (non-linear), revealing the maximum monolayer capacity (Qo) of BBM to be 0,187 mg/g with Langmuir constants KL and aL are 0,215 L/g dan 1,151 L/mg respectively. These value confirms that BBM adsorbent encompasses tremendous potential for mercury (II) ion removal in a solution.