Physicochemical studies of 2-propanol in some micellar solutions (original) (raw)
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Specific conductance of (0.3 to 3.0) mmol Á kg À1 sodium dodecyl benzene sulfonate (SDBS) and (3.0 to 30.0) mmol Á kg À1 dodecyltrimethylammonium bromide (DTAB) has been determined in water and in the presence of (0.01, 0.05 and 0.10) mol Á kg À1 aqueous solution of glutamine/histidine/methionine at T = (293.15, 298.15, 303.15, 308.15 and 313.15) K. From the conductivity data, the critical micellar concentration (CMC) and thermodynamic parameters of micellization (DG o m ; DH o m and DS o m) have been computed by applying the mass action model. Enthalpy–entropy compensation effect has also been observed. The effect of amino acid on the micellar properties of SDBS and DTAB depends upon their nature , concentration, as well as on temperature and has been used to study the interactions present in the micellar systems. There occurs a gradual increase in the value of CMC with temperature in case of SDBS while in case of DTAB, it passes through a broad minimum and then tends to increase with increase in temperature. Increase of amino acid concentration is found to decrease CMC in both the surfactants. The DG o m values are negative and the feasibility of the micellization is found to increase with rise in temperature. The magnitude of hydrophilic and hydrophobic dehydration determines whether the CMC values increase or decrease with rise in temperature.
Journal of Solution Chemistry, 1989
The salt effect of sodium salicylate (NaS) on the micellization and micellar solubilization of sodium dodecylsuIfate (NaDS) has been studied. The experimental and theoretical conditions for the determination of the thermodynamic partition coefficient P of 1-pentanol between the micellar pseudo-phase and water in presence of added salt is discussed in the case of a precise gas-chromatographic method. In particular, it is shown that P decreases with solute concentration in aqueous NoDS and sodium perfluorooctanoate surfactant solutions in opposition to the classical behavior in water-organic immiscible phases. As a reference salt effect, it is shown that P is constant with added NaCl in a large salt concentration domain where NaDS micelles are known to undergo dramatic structural changes. In the case of added NaS, P decreases slightly at very high salt concentration. It is suggested that this behavior might be the consequence of partial mixed micelle formation between the saIicylate ion and NaDS m&elles.
Cationic micelles modulated in the presence of a,x-alkanediols: A SANS, NMR and conductometric study
Journal of Surfactants and Detergents, 2012
The solution behavior of a typical cationic surfactant, tetradecyltrimethylammonium bromide, in mixed solvent systems composed of water and varying concentrations of a,x-alkanediols; 1,2-ethanediol (ED), 1,4-butanediol (BD), 1,6-hexanediol (HD) and 1,8-octanediol (OD) was examined via electrical conductance measurements, 13 C-NMR spectroscopy and small angle neutron scattering (SANS) measurements. The critical micelle concentration (CMC) values and degree of counterion dissociation (a) indicate that both ED and BD oppose micellization, whereas HD and OD enhance micelle formation. Changes in the 13 C-NMR chemical shifts (Dd values) reveal that the short chain diols reside almost exclusively in the bulk phase and hence, affect the formation of micelles by altering the solvent properties in the bulk of the solution, whereas HD and OD partition between the pseudomicellar phase and the bulk phase. SANS studies indicated that both the micellar size and aggregation number (N agg) decrease in the presence of all diols. ED and BD behave like cosolvents and increase the a and CMC values and decrease N agg. We note that the effect of HD and OD on the properties of the micelles is concentration dependent; at low concentrations, these diols interact with the micelles and behave as cosurfactants (as evidenced by the trends in the micellar properties), while at higher concentrations, they enhance the surfactant solubility and behave as a cosolvent.
Journal of Colloid and Interface Science, 2008
Interactions of phenol (PhOH) with micellar aggregates of hexadecyltrimethylammonium bromide (HTAB) in aqueous solutions at surfactant concentrations close to the CMC and phenol contents of 1, 5, or 10 mmol kg(-1) have been investigated at 303 K by means of titration calorimetry, solution conductimetry, and (1)H NMR spectroscopy. Estimates of the main thermodynamic parameters related to HTAB micellization were made for PhOH/HTAB/H(2)O systems based on the specific conductivity measurements and calorimetric determination of the cumulative enthalpy of dilution as functions of the surfactant concentration at a fixed additive content. The combined analysis of the results obtained in H(2)O solutions pointed to the preferential location of PhOH in the outer micelle parts by an enthalpy-driven mechanism. Additional PhOH molecules were located increasingly deeper within the micelle core. The (1)H NMR study of PhOH solubilization by 1.5 mmol kg(-1) HTAB solutions in D(2)O indicated that the two categories of the solubilization site became saturated with the solubilizate already at the lowest additive content. Dissimilar amounts of the solubilized material in H(2)O and D(2)O solutions were ascribed to the difference in the initial micelle structures formed in the two solvents, as inferred from calorimetry and (1)H NMR studies of the HTAB micellization in D(2)O and H(2)O.
Careful measurements of specific conductance of sodium dodecyl sulphate in presence and in absence of sodium Bromide in Methanol-water mixed solvent media containing 0.1, 0.2, 0.3 and 0.4 volume fractions of methanol at 308.15 and 318.15 K are reported. The concentrations of sodium dodecyl sulphate are varied from 9.4x10 -4 to 5.3x10 -2 mol.l -1 .The conductance decreases with addition of methanol. It has been observed that the conductance of sodium dodecyl sulphate increases with increase in concentration as well as with addition of salt(NaBr). The result shows that critical micelle concentration increases with addition of methanol and with rise of temperature and decreases with addition of Sodium Bromide.
The Journal of Chemical Thermodynamics, 2014
Temperature dependence of specific conductivity of sodium dodecylbenzenesulfonate (NaDBS) aqueous solutions was analyzed. Two breaks on the plot appeared for all temperature, which suggest two micellar transitions. This has been corroborated by surface tension measurements. The first transition concentration occurs at the critical micelle concentration (CMC), whilst the second critical concentration (so-called transition micellar concentration, TMC) is due to a sphere-to-rod micelles transition. The dependence of CMC and TMC on the temperature allows the computation of the corresponding thermodynamic functions: Gibbs free energy, enthalpy and entropy changes. For the CMC, enthalpy and entropy increments were found that decrease with the temperature values. However, an anomalous behavior was obtained for the TMC, where both DS 0 and DH 0 values raised with the temperature increase. However, for both transitions, an (enthalpy + entropy) compensation is observed. These results will be compared with similar systems reported in the literature.
Journal of Colloid and Interface Science, 1998
These characteristics depend strongly on the chemical and spa-We report the investigation of the distribution of two stable tial structures of the radical and the microheterogeneous sysnitroxyl radicals, 2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPO) tems. In the present work we report the investigation of the and 4-hydroxy-TEMPO (TEMPOL), between aqueous and miceldistribution of two stable nitroxyl radicals with different hydrolar phases and in the micelle interior by quenching of fluorescence phobicities, 2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPO) of dipyridamole (DIP) and by 1 H NMR, ESR, and optical absorpand 4-hydroxy-TEMPO (TEMPOL) (Fig. 1), between aquetion spectroscopies. Cationic cetyltrimethylammonium chloride ous and micellar phases and in the micelle interior by 1 H NMR (CTAC), anionic sodium dodecylsulfate (SDS), zwitterionic Nand optical absorption spectroscopies, as well as by quenching hexadecyl-N,N-dimethyl 3-ammonio-1-propanesulfonate (HPS), of fluorescence of 2,6-bis(diethanolamino)-4,8-dipiperidinoand non-ionic octylphenoxypolyethoxyethanol (Triton X-l00) micelles were used. In all types of micelles the binding constants for pyrimido [5,4-d] pyrimidine, dipyridamole (DIP), which has more hydrophobic TEMPO appear higher than those for TEMa very high quantum yield of fluorescence in neutral solutions, POL. At the same time the 1 H NMR and optical absorption data high affinity to the micellar phase, and known site of location show that the distribution of both radicals in the micelle interior in micelles (4, 7, 8). On the other hand, DIP is widely used is practically the same: The paramagnetic fragments are localized as a coronary vasodilator (9, 10) and has been considered as in the interface between the polar headgroup region and the hyan antitumor drug coactivator (11, 12). Its antioxidant effect drophobic interior of micelles. There is no clear correlation beand participation in radical reactions have also been docutween K b and the micelle charge. Indeed, K b for TEMPO with SDS mented (13, 14). Thus, the interaction of DIP with free radicals (2150 M 01 ) is lower than with CTAC (3250 M 01 ), but higher constitutes a matter of special interest. Some of the data in than with Triton X-l00 (1300 M 01 ) or HPS (1000 M 01 ). The K b this work are presented in comparison to pyrene fluorescence values correlate quite well with the packing of the monomers in