Modulation in Aggregation Behavior of Cationic Surfactant in Presence of Fluoroquinolone Drug: A Physicochemical Approach

Measurements of density, speed of sound, conductivity, and fluorescence spectroscopy have been carried out to study the interactions between cationic surfactant cetyltrimethylammonium bromide in an aqueous solution of the fluoroquinolone drug at different concentrations and temperatures. Volumetric and compressibility parameters, such as apparent molar volumes ( V _φ ), isentropic compressibility ( κ _s ), and apparent molar isentropic compressibility (κ _{φ, s}) , have been obtained from density and speed of sound. The critical micelle concentration (CMC) of cetyltrimethylammonium bromide (CTAB) is found to decrease with an increase in [antibiotic drug] and increase with an increase in temperature, accounting for the fact that hydrophilic dehydration plays a decisive role for micellization to take place. The various thermodynamic parameters indicate the spontaneity of micellization in the presence of drug moiety. The CMC values have been calculated using pyrene as a fluorescent probe at room temperature, and a good qualitative correlation is found to exist well with the CMC values determined using speed of sound and conductivity measurements.     

Volumetric,speed of sound data and viscosity at (303.15 and 308.15) K for the binary mixtures of N,N-dimethylaniline + aliphatic ketones (C3–C5), +4-methyl-2-pentanone, +acetophenone, +cyclicketones

Measurement of densities (ρ), ultrasonic sound speeds (u) and viscosities (η) has been carried out for binary mixtures of N,N-dimethylaniline (N,N-DMA) with acetone(AC), methylethylketone (MEK), methylpropylketone (MPK), diethylketone (DEK), methylisobutylketone (MIBK), acetophenone (AP), cyclopentanone (CP), cyclohexanone (CH) and 2-methylcyclohexanone (MeCH) and their pure liquids at (303.15 K and 308.15) K over the entire composition range. These experimental data have been used to calculate the excess molar volume (V^E), deviation in ultrasonic sound velocity (Δu), deviation in isentropic compressibility (Δκ_s) and deviation in viscosity (Δη) were evaluated. The variation of these properties with composition of the mixtures suggests dipole–dipole interactions and charge transfer complex formation between N,N-dimethylaniline and ketones. The magnitude of the property is found to depend on the chain length of the ketones molecule. These results have been fitted to the Redlich–Kister polynomial equation. The viscosity data have been correlated using three equations; Grunberg and Nissan, Katti and Chaudhri, Hind et al. for the system studied.     

Ion-solvent interaction: Viscosity and apparent molar volume of univalent electrolytes in dioxane-water mixtures at different temperatures

The viscosity and apparent molar volume of NaCl, NaBr, NaNO₃, KCl, KBr and KNO₃, at mass fractions of dioxane of 10, 20 and 30%, have been studied at 30, 35, 40 and 45°C. The values of the A and B coefficients of the viscosity equation indicate ion-ion and ion-solvent interactions. The limiting apparent molar volume (φ°) and limiting slope (S_v) is found to be different for different salts at different solvent compositions and has also been interpreted in terms of ion-ion and ion-solvent interaction.     

Studies on thermo-acoustic parameters in the dilute solutions of poly(ethyleneglycol)

Ultrasonic velocities and densities have been measured for the dilute solutions of poly(ethylene glycol) of average molecular mass 400 g mol^?1 in benzene at different temperatures between 299 and 328 K. The experimental data have been used to compute the thermo-acoustical parameters namely isentropic compressibility (β), intermolecular free length (L _f), molar volume (V _m), Schoff’s available volume (V _a(s)), acoustic impedance (Z), molar sound velocity (R _a), and molar compressibility (W). Variation of these parameters with temperature of the sample and mole fraction of the solute in the solution, keeping one of the either constant has been discussed to collect the informations on molecular structure and intermolecular interactions.     

Mixed Micellization and Mixed Monolayer Formation of Sodium Cholate and Sodium Deoxycholate in Presence of Hydrophobic Salts Under Physiological Conditions

Mixed micellization and mixed monolayer formation of two bile salts namely sodium cholate (NaC) and sodium deoxycholate (NaDC), in the presence of sodium chloride (NaCl) and three hydrophobic salts including sodium acetate (NaAc), sodium butanoate (NaBu) and sodium hexanoate (NaHx) in 10 mM phosphate buffer (pH 6.5) at 37 °C were investigated by means of surface tension measurements. The experimental results were utilized to evaluate various parameters like critical micellar concentration (CMC), micellar and monolayer interaction parameter (β and β ^σ), micellar and monolayer mole fractions (X and Z), activity coefficients of two bile salts in mixed micelles and monolayer (f and f _(σ)), surface excess (Γ_max) and minimum surface area per molecule of bile salt (A _min). Mixed micelles and mixed monolayer were found to show slight non-ideality and both these phenomena have been found to be affected differently in the presence of various additive salts with NaHx showing larger effects. Higher efficiency of NaHx in affecting both phenomena has been attributed to its appreciable hydrophobicity and surface activity, thus showing stronger interactions with bile salt molecules.     

Mixed Micellization Behavior of (Chlorpromazine Hydrochloride + Cetyltrimethylammonium Bromide) System in Aqueous Solutions of Glycine

We have examined the mixed micellar behavior of {amphiphilic drug; chlorpromazine hydrochloride (CPZ) + cationic surfactant; cetyltrimethylammonium bromide (CTAB)} at varying mole fractions of CPZ (α_CPZ = 0.2, 0.4, 0.6, and 0.8) in (0.1, 0.3, and 0.5) mol kg⁻¹ glycine_(aq) solutions at 298.15, 308.15, and 318.15 K, by using conductometric, volumetric, isentropic compressibility, UV–visible absorbance, fluorescence, and dynamic light scattering (DLS) techniques. The critical micelle concentration (CMC) values obtained from above measurements have been utilized to calculate the thermodynamic parameters (ΔG^°_m, ΔH^°_m, and ΔS^°_m) and degree of ionization (α) at studied temperatures and concentrations. The partial specific volume (φ_v), partial specific isentropic compression (φ_κ), and isentropic compressibility (κ_s) have been calculated from the experimental density and speed of sound measurements and the results have been used to elucidate different interactions occurring in these systems. These results are further supported by UV–visible absorbance and fluorescence spectroscopic studies. The hydrodynamic diameters (D_h) of the mixed micellar system have been measured from the DLS studies. Thermodynamic and spectroscopic studies depict the dominance of hydrophobic/hydrophilic-hydrophobic interactions between the alkyl (R = C₁₆H₃₃) chain of CTAB or hydrophobic tricyclic scaffolding of CPZ/Br⁻/N⁺-CH₃ group of CTAB or hydrophilic group i.e., tertiary amine portion of CPZ with hydrophobic group of glycine.     

Apparent and partial molar volumes of concentrated solutions of some uni-univalent electrolytes in formamide

The density of solutions of NH₄SCN, KSCN, NH₄NO₃, LiNO₃, NH₄ClO₄, NH₄Br in formamide at 25° has been measured in the concentration range going from ≈ 0.5 m up to the saturated solution. By the least-square method the coefficients of the straight lines relating density and concentration have been calculated. It follows that the apparent molar volumes of salts (amv in the investigated concentration range result independent of the concentration, and close to the molar volume of the pure salt. Calculated by the V° (the partial molar volume at infinite dilution) values of the tetraalkylammonium salts and following a Robinson and Stokes suggestion, ionic partial molar volumes (pmv) at infinite dilution agree for both methods. The ionic pmv at infinite dilution follow the Hepler's equation, the A and B coefficients for alkali metal cations and halide anions being independent of the sign of the ionic charge. The value of the A term has been found close to the intrinsic ionic volume plus the volume of the void space which is generated around an ion in a “random close packing distribution”.The low values of the coefficient B, which takes into account the electrostriction of the solvent, has been explained in terms of solvent structure energetically equivalent to the structure of the solution and with the small compressibility of this solvent.     

Synthesis,speed of ultrasound and associated acoustical parameters of epoxy acrylate of 9,9′‐bis (4‐hydroxy phenyl) anthrone‐10 solutions

Density (ρ), viscosity (η), and speed of ultrasound (U) (2 MHz) of pure solvents (chloroform, THF, and 1,4‐dioxane) and solutions of epoxy acrylate of 9,9′‐bis(4‐hydroxy phenyl) anthrone‐10 (EAAN) have been investigated at 303, 308, and 313 K. Specific acoustical impedance (Z), isentropic compressibility (κ_s), intermolecular free path length (L_f), classical absorption coefficient (α/f²)_cl, and viscous relaxation time (τ) have been determined from ρ, η, and U data and are correlated with concentration. Z, (α/f²)_cl, and τ increased with C and decreased with T, while κ_s and L_f decreased with C and increased with T in the solvent systems studied. A fairly good to excellent correlation between a given parameter and concentration is observed in solvent systems studied. Linear increase or decrease of acoustical parameters with concentration and temperature indicated existence of strong molecular interactions. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Volumetric,ultrasonic and viscometric studies of binary liquid mixures of N-ethylaniline + chlorobenzene, + Bromobeneze, + 1, 2-dichlorobenzene + 1, 3-dichlorobenzene+1, 2, 4-trichlorobenzene at 303.15 and 308.15K

We measured densities (ρ), ultrasonic speeds (u) and viscosities (η) for binary binary mixtures of N-ethylaniline (N-EA) with chlorobenzene (CB), bromobenzene (BB), 1,2-dichlorobenzene (1,2-DCB), 1,3-dichlorobenzene (1,3-DCB), and 1,2,4-trichlorobenzene (1,2,4-TCB) and their pure liquids at 303.15 K and 308.15 K. These experimental data were used to calculate the excess volume (V ^E ), deviations in ultrasonic speeds (Δu), deviation in isentropic compressibility (Δ κ _s ), deviation in intermolecular free length (ΔL _f ), deviation in acoustic impedance (ΔZ), deviation in viscosity (Δη) and excess Gibbs free energy of activation of viscous flow (G* ^E ). The variations of these properties with composition of binary mixtures suggest loss of dipolar association, difference in size and shape of the component molecules, dipole-dipole interactions and hydrogen bonding between unlike molecules. The viscosity data were correlated with Grunberg and Nissan, Katti and Chaudhri, and Hind et al. equations and the results were compared with the experimental results. The excess parameters were fitted to the Redlich-Kister polynomial equation using multi parametric nonlinear regression analysis to derive the binary coefficients and to estimate the standard deviation.     

Surface Properties and Micellar Molecular Interaction in Binary Systems of a Biosurfactant Sodium Deoxycholate (NaDC) with Conventional Surfactants

Surface tension for the binary mixtures of a biosurfactant sodium deoxycholate (NaDC) with three different conventional surfactants (p-(1,1,3,3-tetramethylbutyl)phenol polyoxyethylene, polyoxethylene-10-oleyl ether, and sodium oleate) were measured in buffer solutions at different temperatures. Surface properties were determined as well as the micellar characteristics like composition, micellar molecular interaction parameter (??), activity coefficients (f ₁, f ₂), and the free energy of micellization were analyzed using some theoretical models, including Clint, Rubingh, Motomura and Maeda models. The results reveal that all the three investigated systems show non-ideality in the micelle formation by the deviation in the experimental critical micelle concentration (CMC), f ₁, f ₂, and negative ?? values from the ideal values. The proportion of NaDC in the mixed micelle (X ₁) calculated by all models increases with increasing the molar fraction of NaDC in solution (?? _NaDC), but the X ₁ values are very small even at the high ?? _NaDC. Moreover, by using the Maeda theory, the results suggest the chain-chain interaction among surfactants does not seem to be strong. It is noted that two break points were observed in the surface tension plots of pure NaOL and NaDC/NaOL mixture solutions. Interestingly, by introducing moderate NaDC or decreasing the temperature, the first break point disappeared for the two systems.     

Mixed micelles of cationic surfactants and bile acid salts in aqueous media

Critical micelle concentrations of cetyltrimethylammonium-p-toluene sulfonate (CTAT) and cetylpyridinium chloride (CPC) with sodium cholate (NaC) and sodium deoxycholate (NaDC) were determined in aqueous solutions by surface tension measurements. Interaction parameters and mole fraction of the components in mixed micelles were estimated using Rubingh's theory. Strong interaction was observed for each mixed system, a common feature shown by anionic-cationic mixtures. Dramatic effects on the viscosities of these cationic surfactant-bile salt mixtures were seen, and were markedly dependent upon the counterion of the cationic surfactant and the nature of bile salts. Micelles are small and spherical for cationic surfactants in the presence of NaC. Micelle growth was seen for CPC in the presence of NaDC by an increase in viscosity, but a CTAT solution showed an opposite effect on addition of NaDC. Conductance results supported this view. Different behavior of the two bile salts is explained on the basis of their orientation in cationic micelles.     

A Comparative Study of Micellization Behavior of an Ethoxylated Alkylphenol in Aqueous Solutions of Glycine and Leucine

Densities (d) and sound velocities (v) of an ethoxylated alkyl phenol surfactant in aqueous solutions of two amino acids, namely glycine and leucine, have been measured over a temperature range of 25–40 °C at intervals of 5 °C by using density and sound analyzers. Experimental data have been used to calculate the isentropic compressibilities (κ_s), apparent molar volumes (?_v) and apparent molar adiabatic compressions (?_κ) in order to explain amino acid–surfactant interactions. The results have been discussed in terms of the effect of amino acids on the micellization behavior of the surfactant. A comparative study of both the amino acids has been carried out and is found that both amino acids produce a decrease in the CMC value of nonionic surfactant but to different extents.     

Gatifloxacin–Ionic Surfactant Interactions: Volumetric,Acoustic, Voltammetric,and Spectroscopic Studies

Surfactant systems have been frequently used as pseudomodels for investigating interactions of drugs with biological membranes because of their structural similarities with the latter. This helps to understand complicated yet very important biological processes like diffusion of bioactive moieties through biomembranes. The current study deals with voltammetric and spectroscopic studies to evaluate the interaction of a potential antibacterial drug, gatifloxacin (GTF), with a cationic surfactant, dodecyltrimethylammonium bromide (DTAB), and an anionic surfactant, sodium dodecyl sulfate (SDS), under physiological conditions (phosphate buffer, pH 7.4). For more detailed insight into the GTF–ionic surfactant interactions, density and acoustic data were also recorded and used to calculate several important parameters, namely, apparent molar volume (ɸ_V ), isentropic compressibility (K_s ), and apparent molar isentropic compressibility (ɸ_K ) at T = 298.15, 303.15, 308.15, and 313.15 K. Values for partial molar volume (, partial molar expansivity , specific acoustic impedance (Z), relative association (RA), intermolecular free length (L_f), and sound velocity number (U) were also obtained. The interpretation of the concentration dependence of the above-mentioned quantities using a cosphere overlap model led to a better apprehension of solute–solute and solute–solvent intermolecular interactions present in the investigated system, whereas cyclic voltammetry and ultra violet (UV)–visible spectroscopic studies assisted in predicting the location of adsorbed GTF molecules within the DTAB and SDS micelles.     

Change in viscosity of softening coal upon heating with its liquid content. Part I: linear relationship between logarithm of viscosity and liquid fraction

A variable-force-loading needle penetrometry and a proton magnetic resonance analysis were performed for in situ measurements of shear-rate-independent viscosity of softening coal pellet upon heating, η, and the fraction of mobile hydrogen existing in the liquid phase, φ_mh, respectively. During isothermal heating of the pellet at temperature in a range from 680 to 730 K, φ_mh changed with time via a maximum while η did inversely. At every temperature examined, the time for the maximum φ_mh coincided with that for the minimum η. This result qualitatively validated the experimental definition of the liquid fraction in the softening coal as a liquid/solid suspension by φ_mh. Further analysis of the results revealed that the logarithm of η, which changes in a range from 10¹⁰ to 10⁴ Pa s upon isothermal heating, is correlated linearly with the liquid fraction ranging from 0.1 to 0.5. For each of the pellets made of two different coals, it was found that the logarithm η and φ_mh varied being governed by a single linear relationship upon both isothermal heating and non-isothermal heating. Such a single relationship, which was valid over a temperature range from 600 to 800 K, suggested fairly small temperature dependency of the viscosity of liquid in the softening coal.     

The synthesis of (η5-cyclopentadienyl)titanium(IV) alkoxides by alcoholysis of the Ti–π-ligand bond in permethyl η3:η4-allyldiene-(η5-cyclopentadienyl)titanium(II)

The η³:η⁴-allyldiene-(η⁵-cyclopentadienyl)titanium(II) complex [Ti(η⁵-C₅Me₅){η³:η⁴-C₅Me₃(CH₂)₂}] (1) reacts with three molar equivalents of substituted propargylic alcohols FcCCCMe₂(OH) (2a) and PhCCCH₂OH (2b) at elevated temperature to give (η⁵-pentamethylcyclopentadienyl)titanium(IV) alkoxides [Ti(η⁵-C₅Me₅)(FcCCCMe₂O-κO)₃] (3a) and [Ti(η⁵-C₅Me₅)(PhCCCH₂O-κO)₃] (3b), respectively. The crystal structure of 3a has been determined by single-crystal X-ray diffraction.     

Viscosity of bulk free radical polymerizing systems under near-isothermal and non-isothermal conditions

A viscometer-reactor assembly is used to generate data on the viscosity, η(t), of an example polymerizing system exhibiting the Trommsdorff effect, namely, the bulk free radical polymerization of methyl methacrylate (MMA), at different temperature conditions [near-isothermal and non-isothermal (near-step increase and near-step decrease in temperature)] and at two different initiator, 2,2′-azoisobutyronitrile (AIBN), concentrations. Two types of cup and bob assemblies, viz., the Haake^® SV-2 and the Haake^® HV-DIN, have been used to measure η(t) of the reaction mass, until reasonably high values of viscosity, well into the gel effect region. Only three sets of experimental data on x_m(t), M_w(t) and η(t) under near-isothermal conditions, are used to develop general correlations for the viscosity. These tuned correlations predict the values of the viscosity for a whole variety of other experimental conditions, including non-isothermal cases, reflecting that the physics of the system is well represented by them. Hence, these correlations can be used for other systems after tuning their parameters. The feasibility of on-line soft sensing is demonstrated for a few cases.     

Density, ultrasonic velocity, viscosity and their excess parameters of the binary mixtures of N,N-dimethylaniline+1-alkanols (C3-C5), +2-alkanols (C3-C4), +2-methyl-1-propanol, +2-methyl-2-propanol at 303.15K

The density, ultrasonic velocity of sound and viscosity of binary mixtures of N,N-dimethyl aniline (N,NDMA) with 1-propanol, +2-propanol, +1-butanol, +2-butanol, +1-pentanol, +2-methyl-1-propanol, +2-methyl-2-propanol were measured at 303.15 K. These experimental data have been used to calculate excess volume V ^E , excess ultrasonic speeds u ^E , excess intermolecular free length L _f ^E , excess acoustic impedance Z ^E , excess isentropic compressibility κ _s ^E , deviation in viscosity Δη and excess Gibbs free energy of activation of viscous flow (G* ^E ). The values of L _f ^E and κ _s ^E are negative over the wide range of composition for all the binary mixtures, while the values of Z ^E are positive. These results have been used to discuss the nature of interaction between unlike molecules in terms of hydrogen bonding, dipole-dipole interaction, proton-acceptor interaction and dispersive forces. The viscosity data have been correlated using three equations: Grunberg and Nissan, Katti & Chaudhri and Hind et al. The excess/deviations were fitted by a Redlich-Kister equation and the results were analyzed in terms of specific interactions present in these mixtures.     

A general enhancement factor model of the physical absorption of gases in multiphase systems

A general mass transfer enhancement factor model (GEFM) has been developed based on the enhancement mechanism proposed in this paper taking both shuttle effect and hydrodynamic effect into account to calculate the overall enhancement factor due to the presence of dispersed particles. GEFM can describe the phenomena of the enhancement factor increasing with partition coefficient (m), surface covering fraction (α) and dispersed phase volume fraction (φ) increase, leveling off at higher φ, changing of enhancement factor (E) at different conditions. Moreover, GEFM can give the enhancement factor not only of multiphase system relative to the pure liquid phase (even at quite high φ), but also in the same system under different conditions (e.g. stirrer speed, viscosity). The enhancement factors predicted from GEFM are consistent with the experimental observations well.     

Rheology of polymeric solutions I. Zero shear conditions

Based on kinetic considerations, the following equation, connecting the zero‐shear viscosity of polymeric solutions with temperature and the molecular weight and concentration of the polymer was derived: RTln η_R = KBφMⁿ /(1 + BφMⁿ), where η_R is relative viscosity (i.e., the ratio of the solution viscosity to the solvent viscosity); K represents a change in enthalpy of viscous flow from a pure solvent to a pure polymer at the same temperature or from a polymer of low molecular weight (M) to one of higher molecular weight, and has the dimensions of energy (e.g., J/mol) because the ratio BφMⁿ/(1 + BφMⁿ) is dimensionless; φ is the volume or molar fraction of a polymer in solution (concentration units can be used in dilute solutions); B is a constant related to the stiffness of the chains of the polymer in a given solvent; and at BφMⁿ >> 1, ln η_R = K/RT. The equation describes published data on the zero‐shear viscosity of four polar and nonpolar polymers in nine solvents with R² > 0.98. This approach allows the use of solutions of moderate concentrations for the characterization of polymers and opens a way for a single‐point degree of polymerization (DP) determination of polymers at moderate concentrations if constants K, B, and n of the equation are known. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2064–2073, 2002