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We report the synthesis of x = 0.00–1.00 at step size of 0.10 for Ba1-xCaxFe12O19 samples using sol-gel auto combustion method. The powder X-ray diffraction (XRD) data of samples calcined at different temperatures indicates a) single phase formation up to x = 0.20 in samples calcined at 900 °C; b) an increase in calcium solubility to 50 at. % (x = 0.50) at 1200 °C; c) a decrease in lattice parameters ‘c’ (from 23.2002 A (x = 0.00) to 23.0928 A (x = 0.50)) as well as cell volume (from 696.75 A3 (x = 0.00) to 692.95 A3 (x = 0.50)) with increasing ‘x’ and d) the presence of segregated (α–Fe2O3) phase for x ≥ 0.20 at 900 °C and for x > 0.50 at 1200 °C. As the maximum calcium solubility in BaM phase has been noticed at 1200 °C, most of the other characterizations have been performed on these samples only. FESEM micrographs show an increase in particle size with ‘x’. Magnetic measurements reveal that the highest value of saturation magnetization (Ms) is ≈71.82 emu/g (calcined at 1200 °C) in x = 0.50 sample. The coercivity (Hc) decreases from 3765Oe to 1729Oe with increase in ‘x’. Among the samples calcined at different temperatures, the coercivity (Hc) decreases from 4726Oe to 2040Oe with an increase in calcination temperature for x = 0.20 samples. The samples because of their excellent magnetic properties could be vital for magnetic recording and for applications as permanent magnets.

SrFe12O19 samples were initially prepared using sol-gel auto-combustion method and calcined from 500 to 1100°C (for 6 h). XRD data established the phase formation temperature of SrM phase to be ≈1000°C. Thereafter, the effect of Zn2+-Zr4+ co-dopant on magnetic and structural properties of SrZnxZrxFe12-2xO19 (x = 0.00–1.00) samples calcined between 900–1100°C was investigated. XRD data shows that the cell volume increases (from 690.45Å3 (x = 0.00) to 705.72Å3 (x = 1.00)) while crystallite size decreases (from 123.9 nm (x = 0.00) to 62.3nm (x = 1.00)) calcined at 1000°C. The Rietveld refinement of XRD data confirms a) x = 0.00 sample to be phase pure and b) the presence of ZnFe2O4 (≈2.25) & SrZrO3 (≈2.93%) impurity phases in x = 1.00 sample, calcined at 1000°C. FESEM micrographs revealed that a) grain size decreases for x > 0.20 with `x’ at 900°C and b) increases from 122 nm at 900°C to 443 nm at 1100°C, for x = 0.00. Broadening of Raman bands reveals generation of strain in the lattice with enhancement of Zn2+-Zr4+ concentration. The magnetic studies reveal that the coercivity monotonically decreases (from 5358(x = 0.00) Oe to 690(x = 1.00) Oe at 1000°C) with enhancement of Zn2+-Zr4+ concentration. A maximum Ms value ≈ 70.89 emu/g was observed in x = 0.20 sample at 1100°C. Ms value also decreases for x > 0.20 at each calcination temperature.

Personal Protective Equipments (PPEs) are used to safeguard the health of workers. Airborne aerosol with size below 5 micron can enter lower respiratory system directly whereas bigger size particles either settles on surrounding equipment and become fomites. COVID 19 can stay in air after 3 hours with airborne spread in health care with fomites especially plastic showing infection up to 72 hours. Examples of PPE include items as mask, gloves, shield, goggles, gowns and full body suits. All health care workers need to be taught the correct sequence of wearing and taking off the PPE in order to avoid contamination.

The U-type hexaferrites ([Formula: see text][Formula: see text]Co2[Formula: see text][Formula: see text] ([Formula: see text] 0, 0.05, 0.10, 0.15, 0.20, 0.25) have been synthesized by auto-combustion method. The work involves the study of structural, microstructural, dielectric, magnetic and magneto-dielectric properties of the prepared materials. The structural analysis has been done by X-ray diffraction technique along with Le Bail refinement which confirmed the pure hexagonal phase for all the samples. The microstructural analysis has been carried out by field-emission scanning electron microscopy. The vibrating sample magnetometer is used to measure the magnetic properties. The sample with a composition of [Formula: see text] 0.15 has shown the maximum magnetization of approximately 73.31 emu/g with the remnant magnetization of 38.89 emu/g and coercive field of 1.77 kOe at room temperature. Moreover, the same sample has delivered the maximum magneto-dielectric response of about 54.18% at 1.5-T field.

Conductivity and viscosity measurements at 298.15 K were used to investigate the micellization behaviour of anionic surfactant sodium caprylate (SCAP) and cationic surfactant cetyl pyridinium chloride (CPC) in the presence of polymers (polyvinyl pyrrolidone, Tween-20, Tween-40, Tween-60, and Tween-80) in aqueous solutions. For both surfactants, the critical micellar concentration (CMC), critical aggregation concentration (CAC), and polymer saturation point (PSP) have been determined in water and aqueous polymer solutions of various concentrations. The CAC values for both surfactants decreased somewhat as the polymer concentration increased, however the PSP values stayed nearly constant. The degree of ionization (\(\alpha\)) and standard free energy of transfer (\(\triangle\)Go) have been estimated. \(\triangle\)Go values were discovered to decrease as polymer concentrations increased. The relative viscosity, \(\eta\), for the above systems has been determined as well at 298.15 K in various polymer solutions. The maximum value of \(\eta\)I/\(\eta\)I,max (\(\eta\)I is the interaction viscosity) as a function of R (ratio of concentration of surfactant to that of polymer), shifts towards the lower values of R with the increase in polymer concentration. The findings were explored in terms of the numerous interactions that take place in these systems.

In the present work, M-type barium hexaferrite (BaM) was synthesized by sol-gel auto-combustion route using potatoes as Natural fuel. The optimization of fuel (10, 20, 30, 40, 50 g) concentration was carried out. The structural, morphological and magnetic properties of these compounds were investigated. XRD diffractogram reveals pure phase at 30 g potato fuel concentration. SEM micrographs reveals hexagonal and multilobal shape of particles. Magnetic measurements reveal that the values of coercivity (HC) and the saturation magnetization (MS) are highest for BaM synthesized at 30 g fuel concentration.

Supramolecular metallic ensemble (3-Fe2+) has been developed, which exhibited highly sensitive “on–on” response toward creatinine in human blood serum with a detection limit in picomolar range. The...

The major objective of the present investigation to study the effect of Zn/Zr dopant on M type-barium hexagonal ferrites on structure and properties. During present work, we have synthesized a series of BaZnxZrxFe(12-₂x)O19 ferrites (x=0, 0.1, 0.3, 0.5, 0.7, and 0.9) using sol-gel auto combustion method using citric acid as fuel and precursor was calcined at 900°C for 6 hour. These compounds were characterized by FTIR, XRD, VSM, TEM. XRD data of Barium hexaferrite (BAM) material reveals pure phase and have no traces of intermediate phase such as α/γ –Fe2O3 and BaCO3. The BaM series crystal size ranging from 38.9 to 66.9 nm and average size of particle is 49.7 nm. FTIR analysis give information about the functional groups and molecular bands present in the calcined barium hexaferrite material. Magnetic measurements reveal that the values of coercivity ranges viz Hc 4875Oe (x = 0) to 835Oe (x=0.9). The saturation magnetization (Ms) values are in the range of 58.2 to 33.4 emu/g.

Synthesis of BaZn0.6Zr0.6Fe10.8O19 powder samples using sol–gel-auto-combustion method has been reported. The impact of calcination temperature on the structural, magnetic and surface morphology of these samples has been investigated. XRD data confirms that the samples are phase pure and have no traces of intermediate phase such as α/γ-Fe2O3 and BaCO3 etc. The lattice parameters and cell volume increase slightly with increase in calcination temperature. The c/a parameter is

The synthesis of Sr1-xCaxFe12O19 (x = 0.0–1.0 at increments of 0.1) samples is reported via a sol-gel auto-combustion process. XRD data for Sr1-xCaxFe12O19 samples calcined at different temperatures indicates a) single-phase formation up to x = 0.20 in samples calcined at 900 °C, b) an increase in calcium solubility to 50 atomic % (x = 0.50) at 1200 °C, c) a decrease in lattice parameters and cell volume with increasing ‘x’ and d) the presence of segregated α–Fe2O3 phase for x > 0.50 at 1200 °C and for x ≥ 0.20 at 900 °C. As the maximum Ca solubility in SrM (SrFe12O19) phase has been observed at 1200 °C, most of the other characterizations have been performed on these samples only. An increase in grain size with ‘x’ was revealed in FESEM micrographs. Magnetic measurements show that in the x = 0.50 sample the maximum saturation magnetization (Ms) value is ≈ 70.67 emu/g. Coercivity (Hc) decreases monotonically, with an increase in Ca content in SrM (SrFe12O19), from 3822 Oe (x = 0.00) to 2045 Oe (x = 0.50). Among the samples calcined at different temperatures, coercivity (Hc) decreases monotonically from 5650 Oe to 3128 Oe with an increased calcination temperature for samples of x = 0.20. The samples could be vital for magnetic recording and applications as permanent magnets due to their excellent magnetic properties.

Deep eutectic solvents (DESs) constitute a new class of green solvents, the studies on which are going at a fast pace. The binary mixtures of DESs with water are attracting a great deal of interest for various industrial applications owing to their unique properties not exhibited by the neat components. Therefore, thermodynamic properties of DESs-water mixtures should be explored to better understand the prevailing intermolecular interactions for enhancing the application arena of such binary mixtures. Herein, the density (ρ) and speed of sound (u) of binary mixtures of DESs (choline chloride: acetic acid; 1: 2; and choline chloride: L-(+)-lactic acid; 1: 2) with water has been measured over whole composition range at different temperatures (T = 298.15 to 313.15 K) and atmospheric pressure. The values of various thermodynamic parameters have been derived and discussed in terms of the varying extent of intermolecular interactions governed by the components of DESs. The negative values of excess molar volumes ( V m E ) are ascribed to the stronger hydrogen bond interactions and efficient molecular packing in the binary mixtures over repulsive interactions. The V m E values have been analyzed using Prigogine-Flory-Patterson (PFP) theory, which satisfactorily explained the volumetric behaviour of the binary mixtures. Density functional theory (DFT) calculations have been made to support the variation in V m E and the underlying interactions prevailing between the components. Further, isentropic compressibility ( k s ) and excess isentropic compressibility ( k s E ) have been evaluated from the speed of sound data. It is expected that such studies will be beneficial from the academic as well as industrial point of view considering the increasing utilization of DESs for various applications.

Micellization behavior of anionic surfactant sodium caprylate (SCAP) and cationic surfactant cetyl pyridinium chloride (CPC) in presence of polymers (polyvinyl pyrrolidone, Tween-20, Tween-40, Tween-60 and Tween-80) in aqueous solutions has been investigated using conductivity and viscosity measurements at 298.15 K. The critical micellar concentration (CMC), critical aggregation concentration (CAC) and polymer saturation point (PSP) for both the surfactants have been determined in water as well as in aqueous polymer solutions having different concentrations. The CAC values for both the surfactants were found to decrease slightly with increase in polymer concentration whereas PSP values remained almost constant. The degree of ionization (α) and standard free energy of transfer (ΔGot) have been estimated. ΔGot values were found to decrease with increase in polymer concentration. The relative viscosity, ηr, for the above systems has also been determined at 298.15 K in various polymer solutions. The maximum value of ηI/ηI,max (ηI is the interaction viscosity) as a function of R (ratio of concentration of surfactant to that of polymer), shifts towards the lower values of R with the increase in polymer concentration. The results have been discussed in terms of various interactions occurring in these systems.

We report the synthesis of Ba0.5Sr0.5ZnxZrxFe12-2xO19 (x = 0.00–1.00) samples using sol–gel auto combustion method. The Rietveld refinement of XRD data indicates a) pure phase formation, b) increase in lattice parameters with composition and c) the absence of undesirable phases such as α–Fe2O3, BaCO3 and SrCO3. FESEM and TEM micrographs reveal an increase in grain size with ‘x’. The broadening of Raman peaks without any peak shift in all the samples indicates that the Zn2+/Zr4+ions are incorporated into Ba0.5Sr0.5Fe12O19 without altering the local structure. Magnetic measurements reveal that the maximum value of saturation magnetization (Ms) is 67.37 emu/g in x = 0.4 sample. The coercivity (Hc) monotonically decreases from 4.936 KOe to 1.029 KOe with increasing concentration of non-magnetic dopants. The dielectric constant values decreases monotonically as function of frequency for all the samples. The samples because of their superior magnetic properties could be vital for high density perpendicular recording, high density parallel recording EM shielding and permanent magnet applications.

To explore how the solvent characteristics influence the self-aggregation of the cationic gemini surfactant dimethylene-1,2-bis(tetradecyldimethylammonium bromide) (14-2-14) and to obtain various energetic parameters, conductometric experiments were performed on the binary mixtures in the presence of commonly used organic solvents; formamide (FA), acetonitrile (AN) and 2-methoxyethanol (ME) in aqueous solutions at varying temperatures (298.15–323.15 K) and compositions. The procedure suggested by Carpena et al. has been utilized to analyze conductivity–concentration plots in order to obtain critical micelle concentration (CMC) and degree of counterion dissociation (α) of the micelles. This method provides more accurate results as compared to conventional treatments, and the experimental error for the evaluation of micellar parameters is reduced significantly. The results revealed that, although the process of micellization becomes less favorable with the increase in composition of FA, AN and ME in mixed systems, the increase in CMC at compositions lower than 20% (v/v) of the organic solvents is relatively less, indicating that water character is dominant in the bulk phase. As the enthalpy of micellization became more negative, the corresponding entropy change became less positive and enthalpy–entropy compensation phenomenon has been observed for 14-2-14 in all the mixtures within the studied temperature range.

Isothermal titration calorimetry (ITC) has been employed to study the micellization behavior of gemini surfactants ethanediyl-1,2 bis (dimethyldecylammoniumbromide) [10-2-10], ethanediyl-1,2-bis (dimethyldodecylammoniumbromide) [12-2-12], ethanediyl-1,2-bis (dimethyltetradecylammoniumbromide) [14-2-14] in aqueous solutions of different concentrations (0.000, 0.005, 0.010, 0.020 M) of vitamin B3 (nicotinic acid), vitamin B6 (pyridoxinehydrochloride), vitamin B1 (thiamine hydrochloride) in the temperature range (288.15–318.15 K). Various thermodynamic parameters have been derived from the temperature dependence of CMC (critical micellar concentration) values. Enthalpy of micellization values directly obtained from calorimetric experiments have been compared with those derived using van't Hoff method. Thermodynamic, spectroscopic as well as structural parameters have been used to rationalize various interactions occurring in these solutions. Vitamin B1 has been found to facilitate the micellization of gemini surfactants to the maximum extent among the studied vitamins. Parameters obtained from UV - Visible spectra as well as dynamic light scattering studies also support the predominant interactions of vitamin B1with gemini surfactants.

The effect of co-doping of Zn2+/Zr4+ ions on surface morphology, structure and magnetic properties of BaZnxZrxFe12-2xO19 (x=0.00, 0.20,0.40,0.60,0.80, 1.00) synthesized using Pechini method has been investigated. XRD data reveals that the samples are phase pure and have no intermittent phase. The c/a parameter is 2+/Zr4+ dopant seen using FE-SEM micrographs. The local crystal structure distortion with increasing Zn2+/Zr4+ dopant composition is confirm by Raman measurements. M vs H plots reveal that all the samples shows magnetic ordering. The highest Ms value has been noticed to be 68.43 emu/g in x=0.20 sample. The Hc value varies from 5350 Oe to 763 Oe with increase in dopant concentration. These materials have strong potential in magnetic recording applications.

The influence of some salts (NaCl, KCl, $$\hbox {NH}_{4}$$ Cl and $$\hbox {MgCl}_{2})$$ on the critical micelle concentration (CMC) and fraction of counterion dissociation ( $$\alpha $$ ) of sodium dodecylbenzene sulphonate (SDBS) have been determined by conductometric and dynamic light scattering (DLS) methods at 298.15 K. The CMC determination involves fitting of experimental conductivity-surfactant concentration data into the integral form of Boltzmann-type sigmoidal equation. The procedure provides much better results compared to the conventional and differential methods for surfactant such as SDBS that exhibits a gradual transition from pre-micellar to the post-micellar region. The decrease in CMC of SDBS was found to be the highest in the presence of $$\hbox {MgCl}_{2}$$ and least in the case of NaCl among the studied salts. The fraction of counter ion dissociation decreases sharply at lower concentrations of the salts (except NaCl) which have been discussed in terms of effective ionic charge on the micelles. Using CMC and $$\alpha $$ value, the aggregation number of the micelle, micellar surface area and packing parameter has been calculated and were seen to agree well with the corresponding literature values obtained by using fluorescence and surface tension measurements. The effect of salts on the change in micellar size and the surface charge has also been evaluated with the help of DLS experiments and transmission electron microscopy (TEM) images. Synopsis:Precise and iterative procedure was used to calculate the critical micelle concentration and fraction of counter ion dissociation of SDBS micelles in the presence of salts.

The micellization behaviour of sodium dodecyl sulphate, sodium dodecylbenzenesulfonate, hexadecyltrimethylammonium bromide, tetradecyltrimethylammonium bromide, and cetylpyridinium chloride in water and in aqueous solutions of polyethylene oxide (PEO, molecular weight = 100,000) having concentrations (0.005–0.04 %, w/v) has been studied at different temperatures (288.15–318.15 K) using conductivity, surface tension, and viscosity methods. From conductivity measurements various micellar parameters, like critical micellar concentration (CMC), critical aggregation concentration (CAC), polymer saturation point (PSP), degree of ionization (β), and standard free energy of transfer ( $$ \Delta G_{t}^{0} $$ ), have been calculated. CAC values have been found to decrease with polymer concentration and increase with temperature. However, the PSP values increase with both polymer concentration and temperature for all surfactants. Similar parameters have also been calculated from surface tension data (CMCσ, CACσ, PSPσ) along with other parameters such as maximum surface excess concentration at the air/water interface ( $$ \Gamma_{\hbox{max} } $$ ), minimum area per molecule (A min), and packing parameter (p). The CMCσ, CACσ, and PSPσ values are smaller than the corresponding CMC, CAC, and PSP values, but both show similar behaviour with temperature and concentration of polymer. Various parameters indicate that the presence of the aromatic ring in the head group of surfactant decreases its interaction with PEO, whereas the increased hydrophobicity in the tail leads to stronger interactions with PEO. Viscosity studies further supplement the conclusions drawn from the above results.

The interactions in the mixed micelles of two triblock polymers, F68 (EO76PO29EO76) and P123 (EO19PO69EO19), with a series of monomeric (dodecyltrimethyl ammonium bromide, tetradecyltrimethyl ammonium bromide and cetyltrimethyl ammonium bromide) and gemini {dimethylene bis(alkyldimethyl ammonium bromide), m-2-m, where m = 10, 12 and 14} cationic surfactants were studied by surface tension and viscosity measurements in aqueous solutions at different temperatures. The mixed micellar and interfacial properties of the binary mixtures were analyzed using Clint, Rubingh, Rosen and Maeda approaches. Both F68 and P123 show weak interactions with the studied cationic surfactants at 298.15 K which become favorable (synergistic) at higher temperatures. Further, the synergistic interactions are more in mixtures of P123 than F68 at higher temperatures. A comparison of the effects of number of EO and PO blocks in triblock polymers on various physicochemical parameters of the mixed micelles has also been made. The unfavorable enthalpy changes are compensated by favorable entropy changes as a result of the hydrophobic effect. The relative viscosity (η r) studies show that the size of the micelles formed by pure P123 is smaller than those of F68. The values of η r for the mixed micelles of F68 show significant variation with chain length of gemini surfactants whereas no such effect is seen in mixtures with P123.

The mixed micellar and interfacial properties of mixtures of triblock polymer (TBP) with a series of monomeric (dodecyltrimethylammonium bromide, tetradecyltrimethylammonium bromide, and cetyltrimethylammonium bromide, and dimeric (dimethylene bis[alkyldimethylammonium bromide], m-2-m, where m = 10, 12, and 14) cationic surfactants were investigated using surface tension and viscosity measurements in aqueous solutions at different temperatures. Various physicochemical properties such as critical micelle concentration, mixed micellar mole fraction, interaction parameter, interfacial, and thermodynamic parameters were evaluated. All the binary mixtures exhibit synergistic interactions which increase with temperature and pass through a minimum with the increase in hydrophobic chain length of the cationic surfactants. The contribution of TBP in mixed micelle formation also increases with the hydrophobic chain length of the surfactants. The interfacial and thermodynamic parameters reveal that the adsorption of the surfactant mixtures at the air–solution interface is more favorable than that of micelle formation and the unfavorable enthalpy changes are overwhelmed by favorable entropy changes. Further, the mixtures of TBP with smaller chain length surfactants show a sharp rise in relative viscosity at higher mole fractions of these surfactants.

Mixed micellar behavior of gemini surfactant butanediyl-1,4-bis(dimethyldodecylammonium bromide) (12-4-12) with conventional surfactant tetradecyl trimethylammonium bromide (TTAB) has been studied in aqueous and in aqueous polyvinyl pyrrolidone (PVP) solutions at various temperatures (288.15 K, 298.15 K, 308.15 K, and 318.15 K) using conductometric method. The behavior of the mixed system has been analyzed in light of Rubingh's regular solution theory. The study indicates that the above system behaves nonideally with mutual antagonism which increases with temperature. The mixed micelle mole fraction of 12-4-12 has also been determined and is found to be almost same with its ideal state value at all the studied temperatures indicating that mixed micelles are equally occupied by both the surfactants in the whole mole fraction range. In the presence of PVP, the critical aggregation concentration and critical micellar concentration values were found to decrease with increase in mole fraction of 12-4-12 wherea...

The micellar behaviour of similar hydrophobic chain length conventional (cetyltrimethyl ammonium bromide, CTAB; cetyl pyridinium chloride, CPC; cetyldimethylbenzyl ammonium chloride, C16BCl) and gemini surfactant (16-2-16) in water and polar non-aqueous solvents has been investigated in the temperature range 288.15–318.15 K with the help of conductivity measurements. The method proposed by Carpena et al. has been used to analyse the conductivity–concentration to determine the micellization parameters using critical micelle concentration (CMC) and degree of counter-ion dissociation (α) of the micelle. It shows much better performance than the conventional methods and the effect of experimental errors on the evaluation of the micellization parameters has been shown to be minimal by using this procedure. It was observed that the micellization tendency of the surfactant decreases in the presence of solvents. Thermodynamic parameters were also evaluated from the temperature dependence of the CMC values.

Mixed micellization behavior of dimeric cationic surfactants ethanediyl-1,2-bis(dimethyl alkyl ammonium bromide) (m-2-m where m = 10, 12) with conventional single chain cationic surfactants like cetyltrimethyl ammonium bromide (CTAB), cetylpyridinium chloride (CPC), tetradecyl dimethyl benzyl ammonium chloride (C14BCl) and cetyl dimethyl benzyl ammonium chloride (C16BCl) were studied in aqueous and aqueous polyethylene glycol (PEG) solutions at 298.15, 308.15 and 318.15 K respectively using conductometric and viscometric methods. In aqueous solutions, all the combinations (except 12-2-12 + CTAB) were found to behave nonideally with mutual synergism which decreases with increase in temperature. Various thermodynamic parameters of micellization like $$ {{\Updelta}}G_{\text{m}}^{\text{o}} $$ , $$ {{\Updelta}}H_{\text{m}}^{\text{o}} $$ and $$ {{\Updelta}}S_{\text{m}}^{\text{o}} $$ were evaluated and discussed. Similarly in presence of PEG, the thermodynamic properties like $$ {{\Updelta}}G_{\text{t}}^{\text{o}} $$ , $$ {{\Updelta}}H_{\text{t}}^{\text{o}} $$ and $$ {{\Updelta}}S_{\text{t}}^{\text{o}} $$ associated with the transfer of surfactant monomers from the medium consisting of polymer-free mixed micelles to polymer-bound mixed micelles at various temperatures were also calculated. The negative values of $$ {{\Updelta}}H_{\text{t}}^{\text{o}} $$ show that aggregation process is more exothermic than micellization whereas the negative values of $$ {{\Updelta}}S_{\text{t}}^{\text{o}} $$ indicate that the presence of polymer bound mixed micelles decreases the degree of randomness of the system. Viscosity studies show that in aqueous solutions all the combinations of 10-2-10/12-2-12 display negative departure in the relative viscosity (ηr) from additivity rule which decreases with increase in temperature. Similarly in the presence of 5% PEG solutions the magnitude of the negative departure decreases for all the combinations and becomes positive in the case of C14BCl and CPC combinations with the studied gemini surfactants at higher temperatures.

Mixed micellization behavior of dimeric cationic surfactant ethanediyl-1,2-bis (dimethyldodecylammonium bromide) (12-2-12) with a series of monomeric cationic surfactants dodecyltrimethyl ammonium bromide (DTAB), tetradecyltrimethyl ammonium bromide (TTAB), and cetyltrimethyl ammonium bromide (CTAB) has been studied in aqueous and aqueous polyvinylpyrrolidone (PVP) solutions at 298.15, 308.15, and 318.15 K, respectively, using conductometric method. Various thermodynamic parameters like mixed micelle concentration (Cm), micelle mole fraction (X1), interaction parameter (β), and free energy of mixing (ΔGex) of the mixed systems have been determined and analyzed using Rubingh's regular solution theory. The results indicate that in aqueous solutions the binary mixtures of 12-2-12 with DTAB/TTAB behave nonideally with mutual synergism whereas that with CTAB shows almost ideal behavior at 298.15 K. At 318.15 K, all these binary mixtures exhibit antagonistic behavior. The effect of variation in chain length of ...

The apparent molar volumes, apparent molar adiabatic compressibilities, and viscosities of glycine, dl-α-alanine, dl-α-amino-n-butyric acid, l-valine, and l-leucine, in aqueous solutions of cadmium chloride, CdCl2, at different concentrations have been determined in the temperature range (288.15 to 318.15) K from density, sound velocity, and time flow measurements, using a vibrating-tube digital densimeter, ultrasonic multifrequency interferometer, and Ubbelohde type capillary viscometer attached with an automatic viscosity measuring unit, respectively. From these data, partial molar volumes V2o, partial molar adiabatic compressibilities, KoS,2, viscosity B-coefficients, and the corresponding transfer parameters (ΔtVo2, ΔtKoS,2, and ΔtB), hydration numbers, nH, and side chain group contributions, dB/dT have been calculated. Transfer parameters are positive and increase with the concentration of CdCl2.

Mixed micellization behavior of the dimeric cationic surfactant ethanediyl-1,2-bis(dimethyl tetradecyl ammonium bromide) with monomeric cationic surfactants cetyltrimethyl ammonium bromide (CTAB), cetylpyridinium chloride (CPC), tetradecyl dimethyl benzyl ammonium chloride (C14BCl) and cetyl dimethyl benzyl ammonium chloride (C16BCl) was studied in aqueous and aqueous polyethylene glycol (PEG) solutions at various temperatures (298.15, 308.15 and 318.15 K) using conductometric and viscometric methods. The behavior of these mixed systems was analyzed in light of Rubingh’s regular solution theory. The conductivity study indicates that the above systems behave nonideally with mutual synergism at 298.15 and 308.15 K, whereas antagonistic behavior is exhibited at 318.15 K. In the presence of PEG solution, various thermodynamic parameters associated with transfer of surfactant monomers from the medium consisting of polymer-free mixed micelles to polymer-bound mixed micelles like ∆Gto, ∆Hto and ∆Sto at various temperatures were evaluated and discussed. The viscosity study shows that in aqueous solutions all these combinations exhibit significant negative departure in the relative viscosity (ηr) from the additivity rule at 298.15 and 308.15 K, whereas at 318.15 K these combinations (except in the case of C14BCl) follow the additivity rule. In presence of 5% PEG solution, all the combinations show positive departure from the additivity rule except the combination with C14BCl which shows negative departure at all the studied temperatures.

The micellization behavior of homologous series of cationic surfactants tetradecyl- (C14BCl), hexadecyl- (C16BCl) and stearyldimethyl-benzyl ammonium chloride (C18BCl) in water and in aqueous solutions of polymers such as polyvinyl pyrrolidone (PVP) and polyethylene glycols (PEG-20 and PEG-06) has been studied at 298.15 K using the conductometric method. The same method has also been used to study the mixed systems, that is, C16-C14BCl, C18-C16BCl, and C18-C14BCl over the whole mole fraction range of the higher chain length surfactant at 298.15, 308.15, and 318.15 K in water and in presence of 0.5 and 1.0% PVP by volume at 298.15 K. From these measurements various micellar parameters like critical aggregation concentration (CAC), polymer saturation point (PSP), degree of ionization (ψ), and standard free energy of transfer ( ) have been calculated. The CAC and values were found to decrease with increase in polymer concentration whereas PSP values were found to remain constant except in the case of C14BCl ...

Precise density and viscosity measurements on aqueous solutions of lithium acetate, sodium acetate, potassium acetate, magnesium acetate, and calcium acetate have been carried out in the temperature range of T = (288.15 to 318.15) K using a vibrating-tube digital densimeter and Micro-Ubbelohde type capillary viscometer, respectively. The data have been used to obtain partial molar volumes at infinite dilution, V2o, and viscosity B-coefficients for these salts. The effect of temperature on these thermodynamic properties has been studied by determining the partial molar expansibilities (∂V2o/∂T)P and (∂2V2o/∂T2)P and (∂B/∂T) coefficients. The activation free energies, Δμ20,⧺, for the viscous flow of solutions have also been obtained by application of transition state theory to the viscosity B-coefficient data. The results have been rationalized in terms of various interactions taking place in these solutions.