Properties Of Water In Solutions Research Articles

Structure and Dynamics of Water in Polysaccharide (Alginate) Solutions and Gels Explained by the Core-Shell Model.

In both biological and engineered systems, polysaccharides offer a means of establishing structural stiffness without altering the availability of water. Notable examples include the extracellular matrix of prokaryotes and eukaryotes, artificial skin grafts, drug delivery materials, and gels for water harvesting. Proper design and modeling of these systems require detailed understanding of the behavior of water confined in pores narrower than about 1 nm. We use molecular dynamics simulations to investigate the properties of water in solutions and gels of the polysaccharide alginate as a function of the water content and polymer cross-linking. We find that a detailed understanding of the nanoscale dynamics of water in alginate solutions and gels requires consideration of the discrete nature of water. However, we also find that the trends in tortuosity, permeability, dielectric constant, and shear viscosity can be adequately represented using the "core-shell" conceptual model that considers the confined fluid as a continuum.

Study of the Effect of Europium Acetate on the Intermolecular Properties of Water

This paper investigates the effects of europium acetate and intensive stirring on the intermolecular properties of water in solutions. To do this, we studied aqueous solutions of europium acetate in a wide range of concentrations, which were prepared by serial dilution using a microfluidic unit. Water and similarly prepared water dilutions were used as controls. Raman spectroscopy and infrared (IR) spectroscopy were applied to assess the features of hydrogen bonds formed in the studied solutions. Using Raman spectroscopy, it was shown that intermolecular binding is stronger in solutions of europium acetate of 10–1 M and 10–3 M than in water controls. On the contrary, solutions of europium acetate at a concentration of 10–10 М and some lower concentrations demonstrate weaker hydrogen bonding than in the respective water dilutions, which was shown by both methods. Such differences were observed even in solutions with a calculated concentration of europium acetate below 10–24 M. When comparing water with control dilutions of water, it was established that intermolecular binding is different (stronger or weaker) in high dilutions of water than in water not subjected to the dilution procedure. This indicates that the dilution process itself significantly influences the properties of water in solutions. Additionally, the paper discusses the energy state of water molecules in the studied solutions.

Modified binodal model describes phase separation in aqueous two-phase systems in terms of the effects of phase-forming components on the solvent features of water

The binodal model pioneered by Guan et al. [Y. Guan, T. H. Lilley, T. E. Treffry, J. Chem. Soc. Faraday Trans., 89 (1993) 4283–4298] remains the most successful in regard to the quantitative description of phase diagrams among various theoretical models proposed to describe phase separation in aqueous mixtures of polymers. This is a semi-empirical model based on the assumption that any point on the binodal line may be viewed as a saturated solution of the phase-forming compound-1 in the solution of the phase-forming compound-2. Although this model is originally based on the excluded volume concept, we suggest that the solubility of the compound-1 in solutions of compound-2 may depend on the solvent properties of water in solutions of compound-2. The binodal model described in these terms was very successfully applied to the phase diagrams of aqueous two-phase systems formed by different pairs of polymers (dextran, Ficoll, poly(ethylene glycol)-8000, and Ucon). Phase diagram of a new aqueous two-phase system formed by trimethylamine N-oxide (TMAO) and polypopylene glycol-400 and previously reported phase diagram for system formed by TMAO and poly(ethylene glycol)-600 were also described by this model quite well. It was found that the modified binodal model is also applicable to single polymer-salt and polymer-ionic liquid aqueous two-phase systems. The most important conclusion of our study is that the effects of different compounds (polymers, salts, ionic liquids) on the solvent features of water in their aqueous solutions cause changes in the water structure, resulting in phase separation in the mixtures of these compounds.

Investigating the dependence of polymorphic liquid-liquid transitions on the concentration of amphiphiles in water

A way of identifying polymorphic transitions via the hydrolysis of S-decylisothiuronium chloride and other properties of water in solutions of amphiphiles is described. Features of amphiphile transitions (smoothness, micelle bistability, solubilization hysteresis, the autooscillation of micelles, and fluctuations in the extensive properties of a water and micelle nanosystem ensemble) are discussed.

The properties of water in solutions of hydrophilic polymers

The properties of water in solutions of hydrophilic polymers were compared with those in solutions of their monomeric analogues. The properties of polar groups grafted to polymeric molecules were known to remain unchanged. A comparison of the properties of water in solutions of polymers and the corresponding monomers under equal conditions therefore allowed us to obtain information about the influence of polymeric bonds on the properties of water in solutions of polymers. Proceeding from this, we analyzed the influence of polymeric chains and three-dimensional polymeric network on the activity and concentration of water in solutions of polymers.

The dielectric properties of water in solutions

The dielectric properties of water in solutions

The Dielectric Properties of Water in Solutions

Results of dielectric constant and loss measurements at λ=9.22, 3.175, and 1.264 cm are given for a wide variety of aqueous solutions of ions and organic molecules. The water relaxation time is shortened by positive ions and lengthened by hydrogen bond-forming molecules. The properties of water are treated by a statistical method in which the numbers of molecules in four, three, two, one, and zero-bonded states are estimated from dielectric and latent heat data. Fair agreement with experiment is obtained in calculating the static dielectric constant of ice at 0° and water from 0–370°C, using Kirkwood's dielectric theory and Verwey's calculation of the dipole moment of a four-bonded water molecule. The effects of temperature and solutes on the water relaxation time are discussed in terms of this statistical method. The effective number of water molecules ``irrotationally bound,'' i.e., prevented from turning in the electric field by the ion or the organic molecule, is estimated from the depression of the low frequency dielectric constant, using a dielectric theory of mixtures. This number is zero for uncharged solute molecules but is finite for organic or inorganic ions.