Micellar interactions in water-in-oil microemulsions. 1. Calculated interaction potential

Lemaire, B.; Bothorel, P.; Roux, D.

doi:10.1021/j100229a021

Cited by 180 publications

(121 citation statements)

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“…This densification of the surface layer has consequences for the interparticle colloidal interaction: It has been shown that a density increase of Ϸ1% deepens the interaction potential between micelles of Ϸ5-nm radius from Ϫ1.58 to Ϫ5.51 kT (42). Thus, the density increase ref lected in the SFG spectra leads to an increase in the van der Waals interaction, as will the slow orientational relaxation accompanying the annealing process.…”

Section: Resultsmentioning

confidence: 99%

“…A consequence of this transition is less efficient packing of molecules and hence a decrease in the density of the colloidal boundary layer. It has been shown that density changes of this magnitude (liquid vs. crystalline alkyl chains) can substantially modify the van der Waals interaction potential between colloidal particles (41,42). This modified interaction potential results in a colloidal phase transition to a disaggregated, colloidal gas state.…”

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

Surface molecular view of colloidal gelation

Roke

Berg

Buitenhuis

et al. 2006

Proc. Natl. Acad. Sci. U.S.A.

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We investigate the phase behavior of surface-functionalized silica colloids at both the molecular and macroscopic levels. This investigation allows us to relate collective properties such as aggregation, gelation, and aging directly to molecular interfacial behavior. By using surface-specific vibrational spectroscopy, we reveal dramatic changes in the conformation of alkyl chains terminating submicrometer silica particles. In fluid suspension at high temperatures, the interfacial molecules are in a liquid-like state of conformational disorder. As the temperature is lowered, the onset of gelation is identified by macroscopic phenomena, including changes in turbidity, heat release, and diverging viscosity. At the molecular level, the onset of this transition coincides with straightening of the carbon-carbon backbones of the interfacial molecules. In later stages, their intermolecular crystalline packing improves. It is the increased density of this ordered boundary layer that increases the van der Waals attraction between particles, causing the colloidal gas to aggregate. The approach presented here can provide insights into phase transitions that occur through surface modifications in a variety of colloidal systems.sum frequency generation ͉ surface spectroscopy ͉ transition ͉ nonlinear optical scattering ͉ calorimetry C olloidal dispersions are stable because intimate contact between the dispersed particles is physically barred. Given that the particles remain independent, they can exist in distinct states of aggregation analogous to the phases of molecular matter as follows: isolated as gas particles, condensed as an amorphous liquid, or ordered as a crystal. The macroscopic phase of a colloidal dispersion expresses the balance between interparticle attraction at relatively large separations, interparticle repulsion on close contact, and the energy available as thermal fluctuations. Because of their composite nature, such mixtures offer a unique opportunity to manipulate the interparticle potential energy: Attractive forces can be screened more or less by the dielectric properties of the solvent, and repulsive forces depend on the chosen chemical modification of the particle surface. In addition to their interest as models of phase behavior, surface-functionalized colloids are increasingly used to probe biomolecular interactions (1-3), specifically at (model) membranes (4). In such cases, the extreme sensitivity of a colloidal phase to surface modification can be exploited as a detection method, with dramatic changes in the collective properties (such as phase separation and gelation) indicating, for example, molecular adsorption at the interface.Robust dispersions can be created by attaching a bulky molecular layer to the outer surface of the dispersed particles. Such coatings resist the interparticle van der Waals attraction at close range and prohibit or delay irreversible coalescence (5). Particles that have been sterically stabilized in this way show a rich variety of phase behavior in response to external...

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Surface molecular view of colloidal gelation

Roke

Berg

Buitenhuis

et al. 2006

Proc. Natl. Acad. Sci. U.S.A.

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“…The percolation behavior of AOT/nonionic/IPM/water system is different from those of AOT/nonionic/hydrocarbon oil/water systems [55]. It has been reported that the process of coalescence of droplets followed by exchange of materials is accompanied by oil removal from the interface, and the interfacial fluidity may increase with increasing ease of oil removal [74]. The absorption of oil molecules into the interface increases significantly for oils with smaller chain length than that of the surfactant, which in turn hinders the droplet coalescence process.…”

Section: Water/mixed Surfactants/oil(s)mentioning

confidence: 94%

Water solubilization capacity of mixed reverse micelles: Effect of surfactant component, the nature of the oil, and electrolyte concentration

Paul¹,

Mitra²

2005

Journal of Colloid and Interface Science

103

105

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“…When two micelles touch each other, some D 2 O molecules in the corona region are squeezed out and the overlapping between the PEO coronas of two micelles gives rise to the characteristic short range attraction [47]. Two different hydrogen bonds (HB) characterize the system: the HB among D 2 O molecules and the HB between D 2 O molecules and L64 polymers.…”

Section: Sample Sample Preparation and Experimentsmentioning

confidence: 99%