Viscosity Of Aqueous Solutions Research Articles

Quantitative Prediction of the Structure and Viscosity of Aqueous Micellar Solutions of Ionic Surfactants: A Combined Approach Based on Coarse-Grained MARTINI Simulations Followed by Reverse-Mapped All-Atom Molecular Dynamics Simulations.

We address the problem of the quantitative prediction of micelle formation in dilute aqueous solutions of ionic surfactants using sodium dodecyl sulfate (SDS) as a model system through a computational approach that involves three steps: (a) execution of coarse-grained simulations based on the MARTINI force field (with slightly modified parameters to afford the formation of large micelles); (b) reverse mapping of the final self-assembled coarse-grained configuration into an all-atom configuration; and (c) final relaxation of this all-atom configuration through short-time (on the order of a few tens of nanoseconds), detailed isothermal-isobaric molecular dynamics simulations using the CHARMM36 force field. For a given concentration of the solution in SDS molecules, the modified MARTINI-based coarse-grained simulations lead to the formation of large micelles characterized by mean aggregation numbers above the experimentally observed ones. However, by reintroducing the detailed chemical structure through a strategy that solves a well-defined geometric problem and re-equilibrating, these large micellar aggregates quickly dissolve to smaller ones and equilibrate to sizes that perfectly match the average micelle size measured experimentally at the given surfactant concentration. From the all-atom molecular dynamics simulations, we also deduce the surfactant diffusivity DSDS and the zero-shear rate viscosity, η0, of the solution, which are observed to compare very favorably with the few experimental values that we were able to find in the literature.

Jelatin Çözeltilerinin Dinamik Viskozitesine Yapay Sinir Ağı (YSA) Yaklaşımı: Esnek Hesaplama Çalışması

In this research, we present a multi-layered feed-forward neural network (ANN) model developed for prediction of dynamic viscosity of aqueous gelatin solutions using experimental data collected from a number of measurements. In ANN architecture, shear stress, shear strain, torque of spindle, the angular velocity of spindle together with mass concentrations of gelatin solutions were introduced as input neurons, whereas dynamic viscosity of aqueous gelatin solutions was assigned as a single output neuron to be predicted. Developed ANN model was trained using backpropagation algorithm optimized with Bayesian regulation. Optimal geometry of the hidden layer was first studied to search out the ANN architecture which yields the most accurate performance results. Mean squared error (MSE), mean absolute error (MAE), root-mean-squared error (RMSE), determination of coefficient (R^2), the variance accounted for (VAF) and regression analyses were used as performance assessment parameters for suggested network models. Sensitivity analysis was carried out to investigate the most effective input neuron strongly influencing the performance of the developed ANN model. As a result, the use of 8 neurons in the hidden layer has shown excellent performance results yielding the least MSE and the highest R^2 values compared to other suggested ANN models. Upon sensitivity analysis, the shear rate was found to be the most effective input neuron significantly affecting network performance. ANN-based predicted dynamic viscosity values were found to be in excellent agreement with measured viscosity values, demonstrating the robustness as well as the accuracy of the developed ANN model. Developed ANN model can, therefore, be effectively used to predict the dynamic viscosity of aqueous polymer solutions using the same input and output parameters in specific data range reported in this paper with statistical details.

Molecular Interactions of Non-Steroid Anti-Inflammatory Drug Dolonex in Aqueous Solutions of L-Alanine/L-Valine at Different Temperatures: Viscometric Approach

The viscosities of aqueous solutions of L-alanine and L-valine with non-steroid anti-inflammatory drug dolonex (0.020, 0.040, 0.060 mol kg–1) have been measured at different temperatures (293.15–313.15 K) and at atmospheric pressure. On the basis of experimental results Jones–Dole coefficient-B, viscosity B-coefficient of transfer, activation parameters i.e., free energy of activation of viscous flow per mole of solvent $$\Delta \mu _{2}^{{^\circ \# }}$$ and per mole of solute $$\Delta \mu _{1}^{{^\circ \# }}$$ were determined. The obtained results were discussed in terms of solute–solvent interactions in these solutions. Moreover, structure breaker tendency of solute molecules were obtained by measuring temperature derivative of viscosity B-coefficient.

Microbeads of Sodium Caseinate and κ-Carrageenan as a β-Carotene Carrier in Aqueous Systems

β-Carotene was encapsulated in microbeads formed by ionotropic gelation of multilayered emulsions containing sodium caseinate (Na-CAS) and κ-carrageenan at pH 7 and 3.5. The influence of κ-carrageenan concentration on the morphology of microbeads was studied, as well as the effect of pH on the encapsulation efficiency and rheological properties of microbead suspensions. Most of the microbeads showed monomodal size distribution with a mean particle diameter between 25.3 and 176.1 μm. Microbead morphology was influenced by the κ-carrageenan concentration, as microbeads tended to be larger and more spherical at higher κ-carrageenan concentrations. On the other hand, microbeads were slightly affected by pH, showing similar results for encapsulation efficiency and rheological properties of microbead suspensions in salt solution. The encapsulation efficiency was higher than 60% at both pH values. In addition, rheological measurements indicated that the incorporation of microbeads exerted a slight influence on the viscosity of aqueous solutions, mainly up to the 40% volume fraction. Therefore, these microbeads are promising systems for β-carotene vehiculation in food products without compromising their texture.

Density, Speed of Sound, Viscosity, and Surface Tension of Tetramethylethylenediamine Aqueous Solutions from T = 293.15 to 323.15 K

The characterization of tetramethylethylenediamine + water mixtures in relation to different physicochemical properties (density, viscosity, speed of sound, and surface tension) over the whole range of composition is reported in the present work. Other derivative properties such as molar excess volume and isentropic compressibility coefficient were determined in order to explain the mixture behavior. Experimental measurements were done over the temperature range T = (293-323) K. This type of characterization has an important influence upon process modelization in chemical engineering. ©

Thermo-associating polymers based on cross-linked 2-acrylamido-methylpropane sulfonic acid, part A: Synthesis and solution behavior

A novel thermo-thickening hydrophilic copolymer (CGBA) was prepared by free-radical copolymerization of sodium 2-acrylamido-2-methylpropane sulfonic acid (NaAMPS) with a newly-synthesized thermo-sensitive macromonomer (BA) and cross-linking N,N’-methylenebisacrylamide (MBA) in aqueous solution under optimal conditions. Its aqueous solution viscosity behavior with respect to temperature was preliminarily evaluated in comparison with its cross-linked sulfonated copolymer (CPAMPS) counterpart (without BA side-chains). Particular attention is dedicated to the thermo-thickening of the aqueous copolymer solutions as studied by the viscosity measurements. In pure water, and above 0.5 wt.%, CGBA manifested an abrupt macroscopic property above the critical association temperature (Tcass), while CPAMPS exhibited shear-thinning behavior following an Arrhenius law under the same conditions. The composition and length of BA side-chains were identified as the key parameters to envision the self-assembling behavior of CGBA. The results obtained from complementary experiments, performed by proton nuclear magnetic resonance (1H-NMR), Differential scanning calorimetry (DSC), and pyrene fluorescence showed the phase transition of BA side-chains above the Tcass. In addition, well above the Tcass (70 and 80 °C), the oscillatory shear experiments proved that the storage and loss modulus could be fitted with the single relation time Maxwell model at low frequencies. Furthermore, the magnitude of the thickening effect and the Tcass could be modulated using external factors such as shear rates, salinity, and pH. This, in combination with the cost-effectiveness, and the need to further broaden the established theory of thermo-sensitive comonomer, make this copolymer especially interesting for application not only in polymer flooding, but also in drilling fluid.

Structural Transition in Dilute Solutions of Rod-Like Macromolecules

On the basis of experimental data obtained for the viscosity in aqueous solutions of hydroxypropyl methylcellulose (metolose), it has been found that a structural transition takes place in dilute solutions of rod-like macromolecules with the increasing temperature. Namely, macromolecules form clusters in which they are arranged in parallel to one another. It is shown that this transition is a set of local phase transitions of the first kind.

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.

Effect of Nanoparticles on Viscosity and Interfacial Tension of Aqueous Surfactant Solutions at High Salinity and High Temperature

AbstractSurfactant flooding has widely been used as one of the chemically enhanced oil recovery (EOR) techniques. Surfactants majorly influence the interfacial tension, γ, between oil and brine phase and control capillary number and relative permeability behavior and, thus, influence ultimate recovery. Additives, such as nanoparticles, are known to affect surfactant properties and are regarded as promising EOR agents. However, their detailed interactions with surfactants are not well understood. Thus, in this work, we examined the influence of silica nanoparticles on the ability of surfactants to lower γ and to increase viscosity at various temperatures and salinities. Results show that the presence of nanoparticles decreased γ between n‐decane and various surfactant formulations by up to 20%. It was found that γ of nanoparticles–surfactant solutions passed through a minimum at 35 °C when salt was added. Furthermore, the viscosity of cationic surfactant solutions increased at specific salt (1.5 wt.%) and nanoparticle (0.05 wt.%) concentrations. Results illustrate that selected nanoparticles–surfactant formulations appear very promising for EOR as they can lower brine/n‐decane interfacial tension and act as viscosity modifiers of the injected fluids.

Cyanoflan: A cyanobacterial sulfated carbohydrate polymer with emulsifying properties

The extracellular polysaccharides produced by cyanobacteria have distinctive characteristics that make them promising for applications ranging from bioremediation to biomedicine. In this study, a sulfated polysaccharide produced by a marine cyanobacterial strain and named cyanoflan was characterized in terms of morphology, chemical composition, and rheological and emulsifying properties. Cyanoflan has a 71 % carbohydrate content, with 11 % of sulfated residues, while the protein account for 4 % of dry weight. The glycosidic-substitution analysis revealed a highly branched complex chemical structure with a large number of sugar residues. The cyanoflan high molecular mass fractions (above 1 MDa) and entangled structure is consistent with its high apparent viscosity in aqueous solutions and high emulsifying activity. It showed to be a typical non-Newtonian fluid with pseudoplastic behavior. Altogether, these results confirm that cyanoflan is a versatile carbohydrate polymer that can be used in different biotechnological applications, such as emulsifying/thickening agent in food or cosmetic industries.

Aqueous/brine solutions viscosity and surface properties of hydrophobically modified scleroglucans: Role of grafted chain length

Acyl chlorides with different alkyl lengths (C6, C10 or C18) are grafted onto scleroglucan (Sclg) and aqueous/brine solutions viscosities of modified samples are studied at 25/90 °C. All modified Sclgs solutions show lower viscosities than those of the unmodified Sclg solutions, due to the helix-coil transition caused by the modification. The viscosity of the samples aqueous solutions at 25 °C is increased by increasing the grafted alkyl length. However, the viscosity profiles of the aqueous solutions of modified Sclgs are superimposable at 90 °C. The modified Sclg by C10 moieties exhibits the highest viscosity in the brine solution at 90 °C. The results are interpreted by a model depicting the effects of the alkyl lengths on the distances among the Sclg chains and the chains hydrophobic associations. Moreover, the surface and amphiphilic properties of the modified Sclgs in their aqueous solutions are correlated with their alkyl side chain length.

Stability of aqueous electrolytes based on LiFSI and NaFSI

Through a combination of bulk, interface, and interphase effects, water-in-salt electrolytes, employing a high salt concentration, offer a wider electrochemical stability window than traditional dilute aqueous electrolytes. Here we explore chemical stability, conductivity, viscosity, and electrochemical stability of aqueous solutions of bis(fluorosulfonyl)imide (FSI) salts as electrolytes for lithium-ion and sodium-ion batteries. We demonstrate that the FSI anion is prone to hydrolysis in this environment. However, the kinetics of the reaction strongly depend on salt concentration and nature of the cation. Interestingly, we find that NaFSI solutions are significantly more stable than LiFSI solutions. Highly-concentrated NaFSI solutions also display a wide electrochemical stability window and high conductivity.

Effect of ethanol, glycerol, glucose and tartaric acid on the viscosity of model aqueous solutions and wine samples

Viscosity is a property that exerts great influence on the body of wines, since it affects the sensation of thickness in the mouth. The present study refers to the quantitative correlation of the major components of wine, alcohol, reduced sugar, glycerol and total acidity, in its viscosity. Various model aqueous solutions consisting of these components were prepared and viscosity was measured at 20 °C. Each component was studied either alone or in mixtures with the others. Viscosity of white dry wines samples was also measured. From the experimental results, linear multi-dependence equations were derived, which correlate the viscosity with the concentration of the components of the solutions, each of them alone and in combination. Glucose was found to affect viscosity of model aqueous solutions the most, whereas ethanol had the least effect. The knowledge of these factors may have a practical value in optimizing wine’s body.

Chitosan microcapsule membranes with nanoscale thickness for controlled release of drugs

In this paper, chitosan microcapsules with stable nano-membranes for controlled release of drugs are prepared by a simple one-step microfluidic strategy from oil-in-water (O/W) single emulsion templates. The ultrathin membranes of microcapsules are formed at the interface of the O/W emulsion droplets via the interfacial reaction between chitosan in aqueous phase and terephthalaldehyde in oil core. The membrane thickness can be effectively controlled within 10 nm and accurately regulated at nanoscale from 2.8 nm to 8.0 nm by adjusting the crosslinking time, concentrations of reactant and viscosity of aqueous solution. Among these factors, the membrane thickness is more susceptible to the viscosity of aqueous phase. The stability of the nano-membranes is quite good, which makes the microcapsules exhibit excellent structure integrity during 150 days. Using tea tree oil (TTO) as the model drug, the prepared chitosan microcapsules with nano-membranes show low mass transfer resistance and rapid drug release. The cumulative release rate of TTO from chitosan microcapsules with membrane thickness of 3.1 nm and 4.3 nm reach to 76.1% and 56.6% within 10 h, respectively. The drug release behaviors from the chitosan microcapsules are directly related to the thickness of the capsule membranes, and therefore can also be finely controlled. The thinner the capsule membrane is, the faster the drug release. The initial TTO release rate doubles as the membrane thickness decreases from 4.3 nm to 3.1 nm. In addition, because no surfactant is used in the whole preparation process, the prepared chitosan microcapsules present satisfactory biocompatibility. The results provide valuable guidance for designing and fabricating polymeric microcapsule membranes with controllable nanoscale thickness to enhance their performances in biological and medical applications.

Experimental investigation on CO2 absorption capacity and viscosity for high concentrated 1-dimethylamino-2-propanol–monoethanolamine aqueous blends

Experimental data of CO2 absorption capacity for high concentrated 1-dimethylamino-2-propanol (DMA2P)–monoethanolamine (MEA) aqueous blends are presented under atmospheric pressure in a temperature range of 303.2–323.2 K, at different mass fractions of DMA2P (30 wt%–50 wt%) and MEA (5 wt%–15 wt%). The mass fraction and temperature dependences of the absorption capacity are illustrated. The addition of small amount of MEA into DMA2P aqueous solution leads to an obvious increase in the absorption rate of CO2. However, the absorption rate increases not so significantly when wMEA is of high value. Moreover, the temperature affects the absorption rate not so significantly as compared to solution concentration. The CO2 absorption heat of DMA2P-MEA based on the Gibbs-Helmholtz equation was found to be −55.0 kJ/mol. Besides, the viscosities of both CO2-unloaded and CO2-loaded aqueous solutions were measured and modeled in a temperature range of 303.2–323.2 K, and in atmospheric pressure. The effects of temperature, composition and CO2 loading on viscosities were demonstrated. The Weiland equation gave a good prediction with an average relative deviation of 2.42%. Moreover, the activation energy (Ea) was estimated based on the viscosity.

Study on the Viscosities of MDEA-Amino Acid Ionic Liquid Aqueous Solutions

The viscosities of 1-butyl-3-methylimidazolium glycine ([Bmim][Gly])-N-methyldiethanolamine (MDEA), tetramethyl amine glycine ([N1111] [Gly])-MDEA and l-butyl-3-methyl-imidazolium lysine ([Bmim][Lys])-MDEA aqueous solutions were respectively measured by using the NDJ-5S digital rotational viscometer. The temperatures ranged from 303.2K to 323.2K. The mass fractions of MDEA and amino acid ionic liquids (AAILs) respectively ranged from 0.30 to 0.45 and 0.05 to 0.15. The Weiland equation was used to correlate and predict the viscosities of [Bmim][Gly]-MDEA, [N1111] [Gly]-MDEA and [Bmim][Lys]-MDEA aqueous solutions. The temperature and mass fraction dependences of the viscosity of MDEA-AAIL aqueous solutions were demonstrated on the basis of experiments and calculations.

Viscometric Study of Diluted Aqueous Solutions of Polyethylene Glycols of Different Molecular Weights

Dynamic viscosity and density of aqueous solutions of polyethylene glycols (molecular weights of 1000, 1500, 3000, 4000, 6000) are studied in the range of 293.15–323.15 K and at concentrations of up to 0.001 molar fractions. The experimental data allow calculations of the parameters of viscous flow activation and the partial molar volumes of polyethylene glycol in solutions. The concentration dependences are analyzed. It is shown that solutions transition to a more structured state as the polymer concentration is raised.

Densities and Viscosities for Aqueous Solutions of Sodium Chlorate and Potassium Chlorate + Methanol from (288.15 to 318.15) K at 0.1 MPa

In this work, we present densities and viscosities of aqueous solutions of sodium and potassium chlorate from (288.15 to 318.15) K at molalities from (0.1 to 1) and (0.01 to 0.5) for the aqueous so...

The Structure of Polymer Clusters in Aqueous Solutions of Hydroxypropyl Cellulose

The viscosity, turbidity, and heat capacity of dilute aqueous solutions of hydroxypropyl cellulose have been studied in a concentration interval of 0.047–1.5 g/l and a temperature interval of 20–80 ∘C. The data obtained testify that, if the temperature does not exceed 40 ∘C, hydroxypropyl cellulose molecules are prolate spheroidal globules with semiaxis lengths of 7 and 490 ˚ A. At temperatures above 70 ∘C, the hydroxypropyl cellulose solution consists of clusters; every cluster is composed of 11 globules and has a prolate spheroidal form with semiaxes of 41 and 490 ˚ A. In the temperature interval from 40 to 70 ∘C, the solution concerned contains both globules and clusters, with the concentration of the latter increasing, as the temperature grows.

Shear Viscosity of Aqueous Electrolyte Solutions

The kinematic shear viscosity of aqueous electrolyte solutions has been studied. The temperature dependence of this parameter is shown to be described by an exponential formula at T < Td and a formula of the argon-like type at T > Td, where Td is the temperature of the dipole ordering, in the whole considered concentration interval. Main attention is focused on the peculiarities in the temperature and concentration dependences of the shear viscosity in the argon-like interval. It is shown that the root-like concentration dependence can appear, only if the Debye theory of dilute electrolyte solutions is applicable. Beyond its validity domain, the series expansion of the kinematic shear viscosity in the concentration parameter should have an analytical character. The latter behavior is inherent in the concentration dependence of the shear viscosity in the majority of experiments. The error of reproducing the experimental data did not exceed the experimental one, i.e. it was smaller than 4–5%.