“…The micellar changes during solubilization are also a subject of independent interest. ,− It has been established by several research groups that the solubilization of various oils affects the surfactant micelles in different ways. The aliphatic hydrocarbons are found to increase the micelle radius if the initial empty micelles are spherical. ,− When the empty micelles are relatively large and nonspherical (e.g.…”
By NMR and static and dynamic light scattering we investigated how the micelle size, shape, and aggregation number vary during the solubilization of triolein in mixed aqueous solutions of the nonionic surfactant C12En (n ) 5 or 6) and the nonionic triblock copolymer Synperonic L61 (SL61). The latter was found to strongly accelerate the solubilization, although the copolymer alone is unable to solubilize triglycerides. A series of solutions containing different concentrations of surfactant and copolymer has been studied. The light scattering shows that we are dealing with giant micellar aggregates, each of them containing hundreds to thousands of surfactant molecules and dozens of copolymer molecules. Assuming that the micelles have the shape of prolate ellipsoids, we calculated their length and width. The results indicate that the initial, strongly elongated micelles transform into spherical or slightly ellipsoidal ones at the end of solubilization. The micelle aggregation number and hydrodynamic radius decrease by factors of 2-6 during the solubilization; i.e., one empty micelle splits into several smaller swollen micelles of radius 4-5 nm. The NMR measurements reveal that the equilibrium solubilization capacity (solubilized oil/mol of surfactant) is virtually not affected by the addition of SL61. Hence, the copolymer accelerates the process without influencing its final result; that is, SL61 acts as a promoter of solubilization. The results are used in the subsequent two papers of this series to develop a kinetic model of triglyceride solubilization and to verify it against experimental data.
“…The micellar changes during solubilization are also a subject of independent interest. ,− It has been established by several research groups that the solubilization of various oils affects the surfactant micelles in different ways. The aliphatic hydrocarbons are found to increase the micelle radius if the initial empty micelles are spherical. ,− When the empty micelles are relatively large and nonspherical (e.g.…”
By NMR and static and dynamic light scattering we investigated how the micelle size, shape, and aggregation number vary during the solubilization of triolein in mixed aqueous solutions of the nonionic surfactant C12En (n ) 5 or 6) and the nonionic triblock copolymer Synperonic L61 (SL61). The latter was found to strongly accelerate the solubilization, although the copolymer alone is unable to solubilize triglycerides. A series of solutions containing different concentrations of surfactant and copolymer has been studied. The light scattering shows that we are dealing with giant micellar aggregates, each of them containing hundreds to thousands of surfactant molecules and dozens of copolymer molecules. Assuming that the micelles have the shape of prolate ellipsoids, we calculated their length and width. The results indicate that the initial, strongly elongated micelles transform into spherical or slightly ellipsoidal ones at the end of solubilization. The micelle aggregation number and hydrodynamic radius decrease by factors of 2-6 during the solubilization; i.e., one empty micelle splits into several smaller swollen micelles of radius 4-5 nm. The NMR measurements reveal that the equilibrium solubilization capacity (solubilized oil/mol of surfactant) is virtually not affected by the addition of SL61. Hence, the copolymer accelerates the process without influencing its final result; that is, SL61 acts as a promoter of solubilization. The results are used in the subsequent two papers of this series to develop a kinetic model of triglyceride solubilization and to verify it against experimental data.
“…There are two possible explanations for an increase in electrophoretic mobility of the micelles, i.e., an increase of the negative charge and a decrease of the effective radius of the micelles by the solubilization. It was reported that the solubilization of small amounts of 1-alcohols increases the degree of ionization of SDS micelles 18 and causes an increase or only a few changes in the micellar size. , The increased mobility of the micelles would be attributed to the increase of negative charge of the micelles. 3 Dependence of t s and t mc on total concentrations of benzene (a) and phenol (b) in the running solution.…”
Section: Resultsmentioning
confidence: 99%
“…It was reported that the solubilization of small amounts of 1-alcohols increases the degree of ionization of SDS micelles 18 and causes P ) K 0 /ν surf (6) an increase or only a few changes in the micellar size. 19,20 The increased mobility of the micelles would be attributed to the increase of negative charge of the micelles. The dependence of the solubilization constant of benzene and phenol on the applied voltage was examined.…”
We have devised a new micellar electrokinetic chromatographic method for determination of the solubilization equilibrium constants of neutral solutes in surfactant micelles as functions of the intramicellar mole fraction of the solute. In this method, the running solution in a capillary and in electrode vessels contains the neutral solute as well as the surfactant micelles, and the injected solution contains the surfactant micelles and the dilute marker compounds for aqueous and micellar phases but not the solute. The mobility of the solute can be measured from a negative peak recorded on the chromatogram. The solute concentration in the capillary is established, and the mobility of the micellar phase incorporating the solute, which depends on the intramicellar mole fraction of the solute, can be measured from the migration time of the micelle marker. These merits enable precise determination of the solubilization isotherms. This method has been used to study the solubilization equilibria of benzene, phenol, and a series of aliphatic ketones in sodium dodecyl sulfate solution, and the validity and effectiveness of this method for quantifying solubilization have been verified.
“…1 Heterogeneity in composition that results from the manufacturing process or deliberate formulation of various surfactant types to exploit synergistic behavior are two possible mechanisms by which mixed surfactants can be utilized in practical applications. [1][2][3][4][5][6] One area where the use of an interfacial modifier has been shown to be useful, but not completely understood, is the addition of a copolymer to a biphasic polymer mixture to improve the properties of a two-phase system. There exist contradictory experimental results regarding the ability of a random copolymer to effectively compatibilize an immiscible polymer blend.…”
mentioning
confidence: 99%
“…Mixtures of surfactants are encountered in almost all applications of interfacial modifiers . Heterogeneity in composition that results from the manufacturing process or deliberate formulation of various surfactant types to exploit synergistic behavior are two possible mechanisms by which mixed surfactants can be utilized in practical applications. − One area where the use of an interfacial modifier has been shown to be useful, but not completely understood, is the addition of a copolymer to a biphasic polymer mixture to improve the properties of a two-phase system. − There exist contradictory experimental results regarding the ability of a random copolymer to effectively compatibilize an immiscible polymer blend. − ,,− Explanations that have been proffered to explain this discrepancy have included the difference in the sequence distributions − or the compositional distributions 31 of the copolymers that were used in the experimental studies. Clearly, both types of polydispersity exist in the experimental systems; thus, it is difficult to ascertain the relative importance of both factors from an experimental viewpoint.…”
The importance of the sequence distribution in a copolymer that is used as an interfacial
modifier relative to the importance of its composition polydispersity is examined. Using Monte Carlo
simulation, the microstructure of a copolymer is shown to have a greater influence on the ability of a
copolymer to effectively strengthen a biphasic blend than the compositional polydispersity. Correlation
to experimental studies and implications of these results on the design of polymeric surfactants are also
noted.
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