Abstract:The surface tension of the aqueous solution of dodecyltrimethylammonium chloride (DTAC) and decylammonium chloride (DeAC) mixture was measured as a function of the total molality and composition of the surfactants at 298.15 K under atmospheric pressure. To make clear the miscibility of surfactants, the compositions in the mixed adsorbed film and micelle were calculated by use of the thermodynamic equations developed previously. The results indicated that both adsorbed film and micelle are richer in DTAC molecu… Show more
“…The surface tension at the CMC γ C increases, whileĈ decreases, with increasinĝ X 2 . The change of γ C withX 2 is quite similar to that of the DeAC-DTAC system in our previous paper and explained by the change of micelle composition with increasing the total molality [23]. The total differential of for the present systems is written as…”
Section: Resultssupporting
confidence: 76%
“…5. The PDM of the DAC-TTAC system has a shape of a typical cigar type and reveals that the adsorbed film is enriched in trimethylammonium salts compared with the bulk solution and that the micelle is much more enriched than the adsorbed film similar to the DeAC-DTAC system as shown in previously [23]. In the DAC-DTAC system the micelle is much more enriched in trimethylammonium salts than the adsorbed film but less than the bulk solution [26].…”
“…The surface tension at the CMC γ C increases, whileĈ decreases, with increasinĝ X 2 . The change of γ C withX 2 is quite similar to that of the DeAC-DTAC system in our previous paper and explained by the change of micelle composition with increasing the total molality [23]. The total differential of for the present systems is written as…”
Section: Resultssupporting
confidence: 76%
“…5. The PDM of the DAC-TTAC system has a shape of a typical cigar type and reveals that the adsorbed film is enriched in trimethylammonium salts compared with the bulk solution and that the micelle is much more enriched than the adsorbed film similar to the DeAC-DTAC system as shown in previously [23]. In the DAC-DTAC system the micelle is much more enriched in trimethylammonium salts than the adsorbed film but less than the bulk solution [26].…”
“…Region 2 starts at m̂ = 2.02 mmol kg -1 and ends at m̂ = 300 mmol kg -1 , where γ increases slightly but definitely with the molality. With respect to this increase of γ, we have shown already that the change of surface tension with the total molality above the cmc is related to the changes in the compositions of the mixed micelles and the monomeric solution and is explained by using the surface tension at the cmc versus bulk and micelle compositions diagram. − 6 Surface tension versus total molality curve at X̂ 2 = 0.7012: (1) monomer; (2) monomer + vesicle; (3) monomer + vesicle + micelle coexisting regions.…”
The phase behavior of a very dilute aqueous solution of a sodium decyl sulfate (SDeS)−decyltrimethylammonium bromide (DeTAB) mixture was investigated by the surface tension measurement and partly
by the density measurement. The surface tension γ and density ρ were measured as functions of total
molality of surfactants m̂ and composition of DeTAB X̂
2. Break points were observed on the curves and
identified as the critical vesicle concentration and the concentrations of the initial and final points of the
vesicle−micelle coexisting region, respectively. These break points were plotted against X̂
2, analyzed
thermodynamically, and then compared with the ones in the diagrams predicted from a simple model. The
composition of DeTAB in the vesicles at the critical vesicle concentration (cvc) was obtained from the cvc
versus X̂
2 curve, and it was found out to be 0.5 at almost all X̂
2 values. From the other break point versus
X̂
2 plots, the composition region of the vesicle−micelle coexistence in the phase diagram was suggested
to be from 0.62 to 0.65. Furthermore, vesicle formation was clearly indicated to take place even at X̂
2 =
0.9999, and therefore, the vesicle−micelle transition on the critical aggregation concentration Ĉ versus
X̂
2 curve was expected to sit between X̂
2 = 0.9999 and 1.
“…29 In fact, the phase diagrams for both systems are similar to those observed for mixtures of cationic surfactants having polar head groups of different sizes. [35][36][37] Hence, anesthetics with larger polar head groups may be said to be more geometrically favorable for the formation of spherical micelles than for surface adsorption at the plane interface. Here we assume that the influence of the hydrophobic aromatic rings of the anesthetic molecules is roughly similar to that of the methylene groups of the straight-chain surfactant, judging from the regularity of variation in Γ H vs m curves with X 2 .…”
The incorporation of two micelle-forming local anesthetics,
dibucaine hydrochloride (DC·HCl) and
tetracaine hydrochloride (TC·HCl), into surface-adsorbed films
and micelles formed by decylammonium
chloride (DeAC) was studied by measuring the surface tension of aqueous
solutions of DeAC−DC·HCl and
DeAC−TC·HCl binary mixtures. The quantities of the
anesthetics incorporated into the adsorbed film
and micelle of DeAC were estimated from the compositions of the
anesthetics in the adsorbed film and
micelle, which were obtained by thermodynamic analysis of surface
tension data. The phase diagrams
of surface adsorption and micelle formation constructed on the basis of
composition in the molecular
aggregates indicated that although significant amounts of both
anesthetics were incorporated into the
adsorbed film and micelle, larger quantities of DC·HCl than of
TC·HCl were present in the hydrophobic
environment of the aggregates. The relative ease with which these
two anesthetics were incorporated into
the model membranes correlates with their observed clinical potency.
Interactions between DeAC and
the anesthetic molecules in the adsorbed and micellar states were also
analyzed by calculating the ideal
mixing lines in both states. It was shown that the bulky polar
head groups of the anesthetics were more
favorable for micelle formation than for surface adsorption by
comparing the incorporation of the anesthetics
into the adsorbed film with that into the micelle at the critical
micelle concentration.
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