Fluorescence probe studies of the effect of concentration on the state of aggregation of surfactants in aqueous solution

Lianos, Panagiotis; Zana, R.

doi:10.1016/0021-9797(81)90263-0

Cited by 284 publications

(158 citation statements)

References 40 publications

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“…In fact, the steady-state-quenching data follow the Perrin kinetics 39 as shown in Figure 2. However, in the presence of micellar C 12 E 6 (cmc for C 12 E 6 is 0.06 mM at 20°C 40 ), the quenching is remarkably suppressed (Figures 1 and 2). This indicates that CPC molecules are solubilized in C 12 E 6 micelles, and direct interaction with PyPAMPS is prevented.…”

Section: Resultsmentioning

confidence: 96%

“…At these conditions practically all CPC molecules are solubilized in the micelles (Figure 1), giving an average number of CPC per micelle of about 5, assuming the aggregation number of C 12 E 6 to be 3 × 10 2 . 40 The micelle charge density can be continuously increased by a "type I" titration, 26,27 which involves the addition of CTAC to CPC-carrying C 12 E 6 micelles. These observations indicate that polymer-micelle association can take place solely through hydrophobic interactions of the polymer-bound dodecyl groups with micelles at Y = 0.…”

Section: Resultsmentioning

confidence: 99%

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Interaction of Pyrene-Labeled Hydrophobically Modified Polyelectrolytes with Oppositely Charged Mixed Micelles Studied by Fluorescence Quenching

1998

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Pyrene-labeled hydrophobically modified polyanions were prepared by terpolymerization of sodium 2-(acrylamido)-2-methylpropanesulfonate, N-dodecylmethacrylamide (2.5-7.5 mol %), and N-(1-pyrenylmethyl)methacrylamide (1 mol %). Dynamic interactions of these polymers with mixed micelles of n-dodecyl hexa(oxyethylene) glycol monoether (C 12 E 6 ), cetyltrimethylammonium chloride (CTAC), and cetylpyridinium chloride (CPC) (quencher for pyrene fluorescence) were monitored by fluorescence quenching. The charge on the micelle was varied systematically by varying the mole fraction of CTAC (Y) in the mixed micelle. All quenching experiments were performed at Y < Y p , where Y p is a critical Y at which the polymer-micelle systems undergo macroscopic phase separation. A kinetic model was developed to estimate the binding constant (K) (where K ) k 1 /k -1 ), association rate constant (k 1 ), and lifetime of bound micelle on the polymer (residence time) (1/k -1 ) from steady-state and time-dependent fluorescence-quenching data. This analysis led to the following results: K increases with Y because both k 1 and 1/k -1 increase with Y, k 1 being more dependent on Y than 1/k -1 . K markedly increases with increasing concentration of dodecyl groups in the polymers, even at small Y, indicating a strong enhancement of polymer-micelle interactions by hydrophobic interactions. This large increase in the binding constant arises mainly from a large increase in the residence time with increase in the hydrophobe content in the polymers, 1/k -1 being much more dependent on the hydrophobe content than k 1 . The results indicate that complex formation results from hydrophobic interactions between dodecyl groups and the micelle superimposed on the effect of electrostatic force.

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Section: Resultsmentioning

confidence: 96%

Section: Resultsmentioning

confidence: 99%

Interaction of Pyrene-Labeled Hydrophobically Modified Polyelectrolytes with Oppositely Charged Mixed Micelles Studied by Fluorescence Quenching

1998

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“…Evidence for static quenching by CPC are: (1) the steady-state quenching data follow Perrin kinetics; (2) the fluorescence lifetimes are practically independent of the CPC concentration; and (3) the peak counts in single-photon counting measurements of fluorescence decays decrease with an increase in the CPC concentration. However, in the presence of micellar C 12 E 6 (CMC for C 12 E 6 is 0.06 mM at 20°C [63]), the quenching is remarkably suppressed. This indicates that CPC molecules are solubilized in C 12 E 6 micelles and direct interaction with PyPAMPS is prevented.…”

Section: Absorption and Fluorescence Spectramentioning

confidence: 99%

“…The high efficiency of the cationic quencher CPC, in the absence of C 12 E 6 , is [CTAC]+[CPC]}. Under these conditions, the contribution of CPC to Y is 0.016, and the average number of CPC per micelle (n) is five if the aggregation number of C 12 E 6 is assumed to be 3× 10 2 [63]. When Y B 0.04, the fluorescence is only slightly quenched and the decays are single exponential.…”

Section: Fluorescence Quenchingmentioning

confidence: 99%

Interactions of micelles with fluorescence-labeled polyelectrolytes

Morishima

Mizusaki

Yoshida

et al. 1999

Colloids and Surfaces A: Physicochemical and Engineering Aspect

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Pyrene-labeled polyelectrolytes can be used to study the interaction between the polyelectrolyte and an oppositely charged micelle, if the micelle incorporates a fluorescence quencher. If the charge on the micelle is varied systematically, polymer-micelle complex formation can be observed at some well-defined micelle surface charge density. Applying a kinetic model to steady-state and time-dependent fluorescence quenching data, one can estimate the binding constant (K), association rate constant, and lifetime (residence time). K increases strongly with increase in micelle surface charge density (|) or decrease in ionic strength (v). These effects arise from the dependence of association rate constant and residence time on | and v. While these observations reflect the fundamental electrostatic nature of the interaction, it is also found that micelles preferentially bind to pyrene sites, so that complex formation results from the conjoint action of electrostatic and hydrophobic forces.

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“…In the MD calculations, an aggregation number of 60 was adopted for the present SDS micelle since our previous work, 31 as well as light-scattering experiments 32,33 and timeresolved fluorescence spectroscopy, 34 indicated that the aggregation number is thermodynamically most stable at about 60. Thus, 60 SDS molecules, 8360 solvent water molecules, and one penetrating molecule were contained in a cubic simulation box with the periodic boundary condition.…”

Section: B MD Calculationsmentioning

confidence: 99%

Free energy profiles for penetration of methane and water molecules into spherical sodium dodecyl sulfate micelles obtained using the thermodynamic integration method combined with molecular dynamics calculations

Fujimoto

Yoshii

Okazaki

2012

The Journal of Chemical Physics

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Free energy profiles for penetration of methane and water molecules into spherical sodium dodecyl sulfate micelles obtained using the thermodynamic integration method combined with molecular dynamics calculations K. Fujimoto Science, Nagoya University, Japan (Received 14 October 2011; accepted 5 December 2011; published online 6 January 2012) The free energy profiles, G(r), for penetration of methane and water molecules into sodium dodecyl sulfate (SDS) micelles have been calculated as a function of distance r from the SDS micelle to the methane and water molecules, using the thermodynamic integration method combined with molecular dynamics calculations. The calculations showed that methane is about 6-12 kJ mol −1 more stable in the SDS micelle than in the water phase, and no G(r) barrier is observed in the vicinity of the sulfate ions of the SDS micelle, implying that methane is easily drawn into the SDS micelle. Based on analysis of the contributions from hydrophobic groups, sulfate ions, sodium ions, and solvent water to G(r), it is clear that methane in the SDS micelle is about 25 kJ mol −1 more stable than it is in the water phase because of the contribution from the solvent water itself. This can be understood by the hydrophobic effect. In contrast, methane is destabilized by 5-15 kJ mol −1 by the contribution from the hydrophobic groups of the SDS micelle because of the repulsive interactions between the methane and the crowded hydrophobic groups of the SDS. The large stabilizing effect of the solvent water is higher than the repulsion by the hydrophobic groups, driving methane to become solubilized into the SDS micelle. A good correlation was found between the distribution of cavities and the distribution of methane molecules in the micelle. The methane may move about in the SDS micelle by diffusing between cavities. In contrast, with respect to the water, G(r) has a large positive value of 24-35 kJ mol −1 , so water is not stabilized in the micelle. Analysis showed that the contributions change in complex ways as a function of r and cancel each other out. Reference calculations of the mean forces on a penetrating water molecule into a dodecane droplet clearly showed the same free energy behavior. The common feature is that water is less stable in the hydrophobic core than in the water phase because of the energetic disadvantage of breaking hydrogen bonds formed in the water phase. The difference between the behaviors of the SDS micelles and the dodecane droplets is found just at the interface; this is caused by the strong surface dipole moment formed by sulfate ions and sodium ions in the SDS micelles.

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Fluorescence probe studies of the effect of concentration on the state of aggregation of surfactants in aqueous solution

Cited by 284 publications

References 40 publications

Interaction of Pyrene-Labeled Hydrophobically Modified Polyelectrolytes with Oppositely Charged Mixed Micelles Studied by Fluorescence Quenching

Interaction of Pyrene-Labeled Hydrophobically Modified Polyelectrolytes with Oppositely Charged Mixed Micelles Studied by Fluorescence Quenching

Interactions of micelles with fluorescence-labeled polyelectrolytes

Free energy profiles for penetration of methane and water molecules into spherical sodium dodecyl sulfate micelles obtained using the thermodynamic integration method combined with molecular dynamics calculations

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