Apparent Molar Adiabatic Compressibility Research Articles

Solute–solvent interactions of glycine, L–alanine, and L–valine in aqueous 1–butyl–3–methylimidazolium methylsulfate ionic liquid solutions at different temperatures

The intermolecular interactions of amino acids (glycine, L–alanine, and L–valine) in aqueous solutions of an ionic liquid, 1–butyl–3–methylimidazolium methylsulfate [Bmim][MeSO4] as a function of temperature have been investigated by combination of volumetric and acoustic methods. The density, ρ, and speed of sound, u, of glycine, L–alanine and L–valine in aqueous 1–buytl–3–methylimidazolium methylsulfate solutions have been measured in the temperature interval T = (288.15, 298.15, and 308.15) K and atmospheric pressure. These data have been used to calculate apparent molar volume (V∅), and apparent molar adiabatic compressibility (K∅,s) of these mixtures at different temperatures. Later, the standard partial molar volume (V∅0), standard partial molar volumes of transfer (ΔV∅0), standard partial molar adiabatic compressibility (K∅,s0), and standard partial molar adiabatic compressibility (ΔK∅,s0) of transfer have been determined for these amino acid solutions from density and speed of sound data. Also, hydration number (nH) and various group contribution have been calculated. Finally the results have been interpreted in terms of solute - solvent interactions that exist among the currently investigated systems.

Investigations on molecular interactions of memantine hydrochloride in aqueous solutions by thermophysical methods and molecular dynamics simulations at different temperatures

The density (ρ), speed of sound (u), and refractive index (nD) of aqueous solutions of Memantine hydrochloride with molalities ranging from 0.0 to 0.05 at atmospheric pressure and temperatures between 305.15 and 320.15 K were investigated. The experimental results have been used to compute apparent molar volume (Vφ), limiting values of apparent molar volume (Vφ0), the limiting apparent molar expansibility (Eφ0), Hepler's constant (∂2Vφ0∂T2), apparent molar adiabatic compressibility (kφ), limiting values of apparent adiabatic compressibility (kφ0), specific refraction (RD), molar refraction (RM) and hydration number (nh). These data indicated the existence of substantial solute-solvent interactions in the liquid system, as well as hydrogen bond, dipole-dipole, dipole-induced-dipole interactions and solute structure-making capacity. Good correlations with the experimental studies were observed from molecular dynamics (MD) simulation studies.

Volumetric, Compressibility and Viscometric Approach to Study the Interactional Behaviour of Sodium Cholate and Sodium Deoxycholate in Aqueous Glycyl Glycine.

Viscosity, speed of sound (u), and density (ρ) have been measured in aqueous glycyl glycine solution over a temperature range from 293.15 to 313.15 K with a 5 K interlude to evaluate the volumetric and compressibility properties of bio-surfactants, namely sodium cholate (NaC; 1-20 mmol∙kg-1) and sodium deoxycholate (NaDC; 1-10 mmol∙kg-1). Density and viscosity findings provide information on both solute-solute and solute-solvent types of interactions. Many other metrics, such as apparent molar adiabatic compression (κS,φ), isentropic compressibility (κS), and apparent molar volume (Vφ), have been calculated from speed of sound and density measurements, utilising experimental data. The results show that the zwitterionic end group in the glycyl glycine strongly interacts with NaDC and NaC, promoting its micellization. Since the addition of glycyl glycine causes the bio-surfactant molecules to lose their hydrophobic hydration, the observed concentration-dependent changes in apparent molar volume and apparent molar adiabatic compression are likely attributable to changes in water-water interactions. Viscous relaxation time (τ) increases significantly with a rise in bio-surfactant concentration and decreases with increasing temperature, which may be because of structural relaxation processes resulting from molecular rearrangement. All of the estimated parameters have been analysed for their trends with regard to the different patterns of intermolecular interaction present in an aqueous glycyl glycine solution and bio-surfactant system.

Influence of temperature and concentration on the molecular interactions of pyrrolidinium-based ionic liquid with water and alcohols: An experimental and DFT studies

The purpose of the present work is to explore the influence of concentration and temperature on solute–solvent interactions of binary mixtures of ionic liquid (IL) 1-methyl-1-propyl pyrrolidinium tetrafluoroborate ([MPpyr][BF 4 ]) and water, alcohols (methanol and ethanol) at 298.15, 303.15, 308.15 and 313.15 K under atmospheric pressure. The thermophysical properties such as the apparent molar volume ( V ϕ ), apparent molar adiabatic compressibility ( κ ϕ ), and limiting apparent molar volumes ( V ϕ 0 ), limiting apparent molar adiabatic compressibility ( κ ϕ 0 ), the limiting apparent molar expansibility ( E ϕ 0 ), thermal expansion coefficients ( α P ) were evaluated from experimental density ( ρ ) and speed of sound ( u ) data using suitable Redlich–Mayer type equation. V ϕ 0 and ( κ ϕ 0 ) values explain that the IL-solvent interaction in water, are stronger than the those between either methanol or ethanol with IL. Density functional theory (DFT) results are performed using the B3LYP/6–31++G (d,p) method, shows that the prominent interactions within the IL which are aliphatic C–H···anion interactions while the prominent interactions between the IL and the selected solvents are O − H···anion solute–solvent interactions. More importantly, DFT results confirm the trends observed from experimental findings, that the interaction involving IL in water is stronger than those involving either methanol or ethanol solvent with IL.

Role of electrolyte-drug interactions in solution behavior of antibiotic drug streptomycin sulphate: Density, speed of sound and viscosity studies

The density, speed of sound, and viscosity values have been measured for mixtures of aqueous streptomycin sulphate with six different electrolytes (NaCl, KCl, RbCl, MgCl2, CaCl2 and SrCl2) under atmospheric pressure at various concentrations and temperatures (298.15 to 313.15 K). The experimental density (ρ) and speed of sound (u) data have been used to calculate various derived volumetric and compressibility parameters such as apparent molar volume (φv), isentropic compressibility (κ), and apparent molar adiabatic compression(φκ). Viscosity (η) values are used to calculate relative viscosity (ηr) and viscous relaxation time (τ). The above mentioned parameters have been further utilized to develop an insight into the various interactions like hydrophobic-hydrophobic, hydrophobic-hydrophilic, and hydrophilic-hydrophilic interactions happening in electrolyte-drug-water ternary system. Moreover, the viscosity data have been used to investigating the effect of electrolytes in terms of structure making and breaking properties.

Studies of intrinsic volumes of ethylene glycol and polyethylene glycol–300 molecules in aqueous solutions at 298.15 K: Application of Tammann–Tait–Gibson (TTG) equation of state

Systemic density (ρ) measurements have been carried–out for aqueous solutions of polyethylene glycols (PEG's) with the molar mass 200, 300, 400 and 600 D at (288.15, 293.15, 298.15, 303.15 and 308.15) K and at ambient pressure of 0.1 MPa in dilute solute concentration region (0.0119–0.4941 mol⋅kg−1). The ρ data are used to obtain the apparent molar volume (Vϕ) and partial molar volume (V¯2) of studied PEG's in aqueous solutions at finite concentration as well as at infinitely dilute solutions (Vϕ0) at studied temperatures. The coefficient of thermal expansion (α) for solutions, apparent molar expansivity (Eϕ) and limiting apparent molar expansivity (Eϕ0) for solutes are calculated at 293.15, 298.15 and 303.15 K. The densities of studied PEG's in carbon tetrachloride (CCl4) medium are also measured at 298.15 K. The transfer volume (ΔtrVϕ0) for PEG from pure liquid state to CCl4 and to water as solvent are estimated. The literature data of sound velocity (u), coefficient of thermal expansion (α) and specific heat capacity (CP) for solutions have been utilized to obtain thermodynamic properties like adiabatic compressibility (βad) and isothermal compressibility (βT) in case of aqueous solutions of ethylene glycol (EG) and PEG–300 at 298.15 K. The data are further utilized to obtain apparent molar adiabatic compressibility (KϕS) and apparent molar isothermal compressibility (KϕT) for EG and PEG–300 solute molecules at finite and at infinitely dilute solute concentration (KϕS0 and KϕT0, respectively). Further, the data of KϕT, α and CP data have been utilized to estimate internal pressure Pi (=∂U∂VT) of solutions containing EG and PEG–300 molecules as a function of concentration. The intrinsic volumes (Vint.) of these molecules have been calculated by applying Tammann–Tait–Gibson (TTG) equation of state. It is being observed that intrinsic volume differs appreciably from the value based upon EG and PEG–300 in a liquid state as a standard state. The excess volume change (V¯20E=V¯20-V¯int.0) values are found to be −16.1 and −63.8⋅10–6 m3⋅mol−1 for EG and PEG–300, respectively. Similar calculations made for PEG–300 in CCl4 medium also yield excess volume change of −60⋅10–6 m3⋅mol−1 magnitude. These results are explained on the basis of three dimensional hydrogen bonded structure of EG and the linkage ▪ interaction with solvent water having a presence of helical segments. The inferences drawn will be of help to understand the weak denaturing interactions of glycols in protein denaturation studies.

Volumetric and acoustic studies of glycine in aqueous solutions of sulphathiazole drug at T=(288.15 to 308.15) K

The densities (ρ) and speeds of sound (u) for glycine in aqueous solutions of (0.01, 0.02, 0.03, and 0.04) mol·kg -1 sulphathiazole drug have been measured at T = (288.15, 293.15, 298.15, 303.15 and 308.15) K, using vibrating tube digital densimeter and sound analyser Anton–Paar Model DSA - 5000. The apparent molar properties like apparent molar volume ( ), apparent molar adiabatic compressibility ( ) and the apparent molar volume ( 0 ) and adiabatic compressibility at infinite dilution ( 0 ) of glycine have been determined in water as well as in ternary mixtures containing sulphathiazole drug at different concentrations and at different temperatures from experimental data of densities and speeds of sound under atmospheric pressure. These data were also used to calculate the transfer parameters. Transfer parameters have been explained from the point of view of concentration dependence of solute-solute and solute-solvent interactions. The limiting apparent molar expansibility ( ) values for glycine in aqueous solutions of drug have been calculated. The calculated values of thermal expansion coefficient ( ) have small and positive values. These results are explained on the basis of drug-amino acid - water interactions and hydrophobic –hydrophilic interactions.

Studies of internal pressure in aqueous solutions of a surfactant (decyltrimethylammonium bromide) at 298.15 K: Understanding and use of Gibson−Tait equation

Recently reported literature density (ρ), thermal coefficient of expansion (α) data for aqueous solutions of decyltrimethylammonium bromide (C10TAB) in limiting concentration range (0.01 to 0.15 mol kg−1 comprising both pre-micellar and post-micellar regions) have been used and combined with literature density, adiabatic compressibility (βS) and specific heat capacity data (Cp), to calculate isothermal compressibility (βT) and internal pressure (Pi) properties of solutions. The variations of apparent molar adiabatic compressibility (Kϕs) of solute, apparent molar isothermal compressibility (KϕT) of solute and internal pressure (Pi) of solutions are studied and used to obtain infinite dilution parameters such as limiting apparent molar adiabatic compressibility (KϕS0) of C10TAB. The Tammann−Tait−Gibson (TTG) model is applied to calculate the excess volume change for the electrolyte (ΔV¯2E) and intrinsic volume (Vint.) of the cationic surfactant both in pre-micellar and post-micellar regions of concentration. A new method based on internal pressure of solutions and an approach by Tanford incorporating alkyl chain volume, length and head group is developed and used to obtain radius of the micelle and aggregation number. From these data, it is concluded that the micelles are small, spherical and incorporating the surface area of the head group. Our proposed method provides a framework for examining the thermodynamic properties of surfactant in terms of equilibria of the monomer (in limiting range of concentration) and the micelle aggregates after critical micelle formation (cmc) (post-micellar region). In pre-micellar region, water structural changes are important and the hydration of the cations is determined by hydrophobic van der Waal's forces, of which extent increases after cmc, resulting in self-assembly in the form of micelle. Volume changes due to transfer of an electrolyte C10TAB from a liquid hydrocarbon like environment to aqueous solutions and to interior of micelle are also estimated and found to be of positive magnitude.

Study of ternary association of anti-microbial drug 1, 10-phenanthroline and α - amino acid with copper salt, an ultrasonic investigation of competitive interaction

Molecular interaction studies using ultrasonic technique and spectroscopic investigation in ternary liquid mixture of drug 1,10-Phenanthroline, an α- amino acid Glycine and a transition metal salt like CuCl2 in aqueous medium has been carried out at 300.15K and 2 MHz frequency. Using experimental values of density (ρ),ultrasonic velocity (U) and UV analysis, different acoustical parameters such as adiabatic compressibility (β),intermolecular free length (Lf), acoustic impedance (z),relative association (RA),apparent molar volume (V∅), apparent molar adiabatic compressibility (K∅) are evaluated for the mixture of drug, glycine and inorganic salt CuCl2 at various concentrations. The ultrasonic and spectroscopic investigation clearly shows coordinative association of drug as a ligand with transition metal salt. Further interaction of glycine as an α- amino acid indicates a competitive association in the ternary system. The outcomes were expressed in terms of molecular interactions and the variation in parameters under varying solute concentrations providing conclusive remarks regarding the strength of intermolecular interactions in the ternary system with a bio-physical novelty.Â

Studies on Acoustic and Aggregation Properties of Sodium Dodecyl Sulfate in Amino Acid Solutions through Ultrasonic Velocity Technique

Acoustic and aggregation properties of sodium dodecyl sulfate in aqueous amino acid systems have been studied through ultrasonic velocity techniques at different temperature as a function of concentration and at different temperature (288.15, 293.15, 298.15, 303.15, 308.15, 313.15, 318.15 and 323.15 K) and atmospheric pressure using density and sound velocity analyzer (DSA 5000, Anton paar, Austria). Densities and ultrasonic velocity of sodium dodecyl sulfate in aqueous amino acid have been measured and from the experimental data, adiabatic compressibility (βS), apparent molar adiabatic compressibility (φk), critical micelle concentration (CMC), acoustic impedance (Z), relative association (RA) and molar sound velocity (Rm) have been calculated. The results show significant information about acoustic properties of sodium dodecyl sulfate (solute-solute interactions, aggregation behaviour, relative association and structure formation) in aqueous and aqueous amino acid solution.

Intermolecular interactions between methanol and some sulphonamide drugs in aqueous medium using thermodynamics approach

Interactions between methanol and some sulphonamide drugs namely sulphamethizole, sulphabenzamide, sulphaquinoxaline and sulphachloropyridazine were investigated. Physical parameters such as densities (ρ), sound velocities (u) and viscosities (ƞ) were measured, and the effects of temperature and concentration on aqueous phase interactions were deduced. Other physical quantities like apparent molar volumes, Vφ, apparent molar adiabatic compressibilities, kφ, viscosity B-coefficients and temperature coefficient (dB/dT) were derived from measured data. Corresponding partial molar quantities were determined by employing Redlich-Mayer type equation. Sulphamethizole and sulphabenzamide are regarded as structure breakers based on positive values of dB/dT, while sulphaquinoxaline and sulphachloropyridazine are considered to be structure makers due to negative values of dB/dT.

Thermo-acoustical and volumetric studies on interionic interactions of l-histidine in aqueous maltose solutions at different temperatures

Apparent molar volumes, Vφ and adiabatic compressibilities, Ks, φ of l-histidine in the concentration range (0.0 to 0.18 mol kg−1) in maltose solutions ranging from pure water to 20.0 mass % of maltose have been calculated at 298.15, 303.15, 308.15 and 313.15 K from precise measurements of density and speed of sound. At infinite dilution apparent molar volumes, Vφ0, and apparent molar adiabatic compressibilities, Ks, φ0, of l-histidine have been also evaluated. Transfer volumes, ΔtrVφ0, and transfer adiabatic compressibilities, ΔtrKs, φ0, at infinite dilution from water to aqueous maltose solutions have been also calculated. Solute-solvent interaction has been confirmed with the positive value of Vφ in all the systems. Besides the reported values of Ks, φ were negative for l-histidine in aqueous-maltose solutions, indicating that the water molecules around ionic charged groups of amino acids are less compressible than the water molecules in the bulk solution. Interaction between saccharides and proteins molecules is expected to create polar environment, which helps to increase the hydrophobic interactions because of stabilizing the protein. The results indicate there exists strong solute–solvent (hydrophilic–ionic group and hydrophilic–hydrophilic group) interactions in these systems, which increase with increasing in saccharide concentration. It has also been observed that l-histidine acts as structure maker in aqueous-maltose solvents.

Ultrasonic Characterization of Newtonian and Non-newtonian Fluids

Viscous liquid causes a loss of acoustic energy for acoustic wave propagation through the liquid. From an acoustical point of view, Glycerin being Newtonian is a more complex medium as it is heterogeneous, anisotropic and viscoelastic. Non-Newtonian liquids like PEG-SiO2, DMF-SiO2 solutions show shear-dependent nonlinear Viscosity. Apparent molar adiabatic compressibility ( ), as well as bulk moduli (K) and apparent molar volumes ( ) of different glycerin-water solutions, are evaluated in the present investigation. At the lower concentration region for glycerin-water solutions apparent molar adiabatic compressibility ( ) varies linearly with the independent variable either molality or m1/2. The pulse-echo method has been followed to measure attenuation coefficient and sound velocity in these liquids at room temperature. This sound velocity has been compared with the measurement from high precision density and velocity meter (Anton Paar DSA 5000 M for the same temperature. The measurement technique has been reported to quantify adiabatic compressibility as 10% glycerin in water was found to be 41.1×10-11 Pa-1 (K=2.43GPa) including 1.86dB/cm/MHz of attenuation, less compared to pure water but the ultrasonic absorption coefficient (μa ≈ 0.53) of 10% glycerin in water is nearer to pure water whereas the Non-Newtonian fluids show higher attenuation (>3dB/cm) and higher absorption (μa≈0.6).

Investigation of Volumetric and Acoustic Properties of Ionic Liquid + Amino Acid + Water Systems at Different Temperatures

This paper reports density and speed of sound data for solutions of the ionic liquids (ILs) [C4mim]Cl and [C4mim][CF3SO3] in aqueous solution of 0.05 w/w amino acids of alanine, serine and proline at T = (288.15, 298.15, 308.15 and 318.15) K. From the experimental data measured, the apparent molar volume (Vϕ), isentropic compressibility ( ), and apparent molar isentropic compression ( ) have been calculated. The Vϕ values of [C4mim]Cl and [C4mim][CF3SO3] in the investigated aqueous amino acid solutions decreased by increasing the hydrophobicity of the amino acid and follow the order: serine ˃ alanine ˃ proline. The apparent molar volume and isentropic compressibility values at infinite dilution of the investigated ILs in the aqueous amino acid solutions and their variations with temperature have been determined. The infinite dilution apparent molar volume and adiabatic compressibility for transfer of the studied ILs from water to aqueous solutions of the amino acids have been calculated and the results were discussed in terms of different interactions existing in these solutions.

Physicochemical properties of L-carnitine in aqueous solution and its interaction with trimethylamine N-oxide, sodium chloride and dextrose: Volumetric and calorimetric insights

Abstract L -carnitine plays physiologically important roles specifically to decrease triglycerides, very low density lipoprotein (VLDL) and cholesterol. Considering these facts, it is believed to be helpful in the reduction of cardiovascular diseases and diabetes. Physicochemical properties of L -carnitine in aqueous or mixed aqueous solutions are scarcely available in literature. Such properties will be useful in understanding the interactions of L -carnitine with other cellular components like trimethylamine-N-oxide (TMAO), dextrose ( D -glucose) and NaCl. The values of densities (ρ) and speeds of sound (u) of L -carnitine were measured over the molality range of m = 0.05 mol·kg−1 to m = 0.3 mol·kg−1 at temperature T = 293.15 K to T = 313.15 K in water and in aqueous solutions of TMAO, dextrose, and NaCl. Using these data, values of apparent molar volume (V2,m,φ) and apparent molar adiabatic compressibility (Ks,2,m,φ) have been determined. The results obtained from these measurements have been used to derive the standard partial molar volume ( V 2 , m o ), standard partial molar adiabatic compressibility ( K s , 2 , m o ), standard partial molar volume of transfer ( Δ tr V 2 , m o ) and standard partial molar isentropic compressibilities of transfer ( Δ tr K S , 2 , m o ) from water to aqueous solutions of TMAO, dextrose, and NaCl. Through Isothermal Titration Calorimetry (ITC), the enthalpies of dilution ( Δ dil H m ) of L -carnitine in water (over a temperature range of T = 293.15 K to T = 313.15 K) and in aqueous solutions of TMAO, dextrose, and NaCl have been determined. The values of standard molar enthalpy of dilution ( Δ dil H m o ) and their transfer values ( Δ tr Δ dil H m o ) have been derived from these measurements. The results have been discussed in terms of possible intermolecular interactions. The data suggest that there is overall balancing of hydrophobic and hydrophilic interactions in system containing L -carnitine and TMAO in aqueous solution, but hydrophobic effect dominates when the co-solute is NaCl or dextrose.

Temperature-dependent aggregation of bio-surfactants in aqueous solutions of galactose and lactose: Volumetric and viscometric approach

Abstract Modulation in the aggregation behavior of bio-surfactants (bile salts), sodium cholate (NaC) and sodium deoxycholate (NaDC) in aqueous solutions of carbohydrates (galactose and lactose) have been investigated by measuring the density (ρ), speed of sound (u) and viscosity (η) of the mixtures at different temperatures 293.15, 298.15, 303.15, 308.15 and 313.15 K. The density and speed of sound data have been used to calculate various volumetric and compressibility parameters such as apparent molar volume (Vφ), isentropic compressibility (κs), apparent molar adiabatic compression (κs, φ) to get a better insight into the micellization mechanism of bile salts. Further, the viscosity data have been studied in the light of relative viscosity (ηr) and viscous relaxation time (τ). Some derived parameters such as free volume (Vf), internal pressure (πi) and molar cohesive energy (MCE) of NaC and NaDC in aqueous solution of saccharides have also been calculated from viscosity data in conjunction with density and speed of sound values. All the calculated and derived parameters provide qualitative information regarding the nature of interactions i.e. solute–solute, solute–solvent and solvent–solvent in the solution.

Exploration of Diverse Interactions of Some Vitamins in Aqueous Mixtures of Cysteine

The apparent molar volume (ΦV), viscosity B-coefficient, molal refraction (R) and adiabatic compressibility (ΦK) of Nicotinic Acid, Ascorbic Acid, and Folic Acid have been determined in 0.01, 0.03, 0.05 mol∙dm-3 aqueous Cysteine solutions at 298.15 K from density (ρ), viscosity (η), refractive index (nD) and speed of sound (u) respectively. The limiting apparent molar volumes (Φ0V) and experimental slopes (S*V), derived from the Masson equation, have been interpreted in terms of solute-solvent and solute-solute interactions respectively. The viscosity data were analyzed using the Jones-Dole equation and the derived parameters A and B have also been interpreted in terms of solute-solute and solute-solvent interactions respectively in the solutions. Using the Lorentz-Lorenz equation, molal refractions (R) have been calculated. At infinite dilution, limiting apparent molar adiabatic compressibilities (Φ0K) of these vitamins were evaluated and discussed.

Volumetric, Acoustic and Transport Properties of Metformin Hydrochloride Drug in Aqueous d-Glucose Solutions at T = (298.15–318.15) K

Apparent molar volumes, apparent molar adiabatic compressibilities and viscosity B-coefficients for metformin hydrochloride in aqueous d-glucose solutions were determined from solution densities, sound velocities and viscosities measured at T = (298.15–318.15) K and at pressure p = 101 kPa as a function of the metformin hydrochloride concentrations. The standard partial molar volumes ( $$ \phi_{V}^{0} $$ ) and slopes ( $$ S_{V}^{*} $$ ) obtained from the Masson equation were interpreted in terms of solute–solvent and solute–solute interactions, respectively. Solution viscosities were analyzed using the Jones–Dole equation and the viscosity A and B coefficients discussed in terms of solute–solute and solute–solvent interactions, respectively. Adiabatic compressibility ( $$ \beta_{s} $$ ) and apparent molar adiabatic compressibility ( $$ \phi_{\kappa }^{{}} $$ ), limiting apparent molar adiabatic compressibility ( $$ \phi_{\kappa }^{0} $$ ) and experimental slopes ( $$ S_{\kappa }^{*} $$ ) were determined from sound velocity data. The standard volume of transfer ( $$ \Delta_{t} \phi_{V}^{0} $$ ), viscosity B-coefficients of transfer ( $$ \Delta_{t} B $$ ) and limiting apparent molar adiabatic compressibility of transfer ( $$ \Delta_{t} \phi_{\kappa }^{0} $$ ) of metformin hydrochloride from water to aqueous glucose solutions were derived to understand various interactions in the ternary solutions. The activation parameters of viscous flow for the studied solutions were calculated using transition state theory. Hepler’s coefficient $$ (d\phi /dT)_{p} $$ indicated the structure making ability of metformin hydrochloride in the ternary solutions.

Volumetric, compressibility, surface tension and viscometric studies of CTAB in aqueous solutions of polymers (PEG and PVP) at different temperatures

In the present manuscript, we intend to examine the effect of neutral polymers (polyethylene glycol and polyvinyl pyrrolidone) and their blends on the post-micellization of the cationic surfactant, CTAB using conventional techniques such as density, speed of sound, surface tension and viscosity. From the parent data of density and speed of sound, we evaluated the volumetric parameters, namely apparent molar volume volumes (ϕv) and adiabatic molar compressibility (ϕk) along with various acoustical parameters of importance. The volumetric properties reveal different kinds of interactions that are present in the ternary system especially at lower and higher surfactant concentration without taking into consideration the post-micellar effect. Surface tension further strengthens the effect of these polymers in terms of electrostatic and hydrophobic interactions which show that surface tension decreases as the PEG content increases in the polymer mixture as compared to PVP. This may be due to the presence of residual positive charge on the PVP molecule which makes it less interactive towards the cationic surfactant. Viscosity result are further analysed in terms of relative viscosity (ηr) and viscous relaxation time (τ). All these parameters form the basis of the discussion of the effect of these neutral polymers on the physical properties of CTAB. The effect of temperature has also been discussed.

Surface, compressibility and viscometric measurements of binary system containing cationic surfactant with achiral amino acid at different temperatures

In the preset manuscript, we intend to examine the type of solute-solvent interactions present in such system which is valuable to food/pharmaceutical sector. A systematic knowledge of the volumetric properties in conjunction with other thermodynamic properties provides useful information about water-solute interactions. We examine, therefore, surface tension, density, speed of sound and viscosity for binary system contains cationic surfactant cetyltrimetylammonium bromide (CTAB) in aqueous glycine solution (0.2, 0.3 and 0.4) mol/kg at four different temperatures ranging from (298.15 to 313.15) K. The surface tension result indicates the change in critical micelle concentration (CMC) values in the presence of additive. Various thermodynamic and adsorption parameters like surface excess, Γmax, minimum area at air-liquid interface, Amin etc. have been evaluated form surface tension data. The density and speed of sound measurements have been used to calculate the apparent molar volume and adiabatic compression which reveals the kind of interactions present pertaining to hydrophilic-hydrophillic and ion-hydrophillic interactions. In addition, hydrophobic hydration also plays a key role especially at higher surfactant concentration. Viscosity data further strengthen the concept of hydrophobic interactions present in the binary solution taken into consideration the relative viscosity and viscous relaxation time parameters. The effect of temperature and additive for all the calculated parameters has also been discussed in detail.