Relationship between microemulsion structure and surfactant layer bending elasticity

doi:10.1016/0378-4371(90)90371-X

Physica A: Statistical Mechanics and its Applications

Volume 168, Issue 1, 1 September 1990, Pages 210-219

https://doi.org/10.1016/0378-4371(90)90371-X Get rights and content

Abstract

We recall briefly the knowledge on microemulsion structure emphasizing the importance of the surfactant layer properties. We present results of experiments made with water-alkane-non-ionic surfactants systems that, together with results obtained earlier in other systems, confirm the close relationship between the maximum characteristic size in the microemulsion and the persistence length of the surfactant layer. The possible influence of the Gaussian bending elastic modulus is discussed.

References (23)

P.G. de Gennes et al.
J. Phys. Chem.
(1982)
D. Langevin
Accounts Chem. Res.
(1988)
S.A. Safran et al.
Phys. Rev. Lett.
(1983)
W. Helfrich
Z. Naturforsch.
(1973)
J. Jouffroy et al.
J. Phys. (Paris)
(1982)
B. Widom
J. Chem. Phys.
(1984)
W. Helfrich
J. Phys. (Paris)
(1985)
L. Peliti et al.
Phys. Rev. Lett.
(1985)
S.A. Safran et al.
Phys. Rev. Lett.
(1986)
B. Widom
J. Chem. Phys.
(1986)

K.A. Dawson

Phys. Rev. A

(1987)

Cited by (16)

The formation of complex droplets in liquid three phase systems and their effect on dispersion and phase separation
2018, Chemical Engineering Research and Design
Citation Excerpt :
Regular emulsions (e.g., macroemulsions) and microemulsions are fundamentally different, because microemulsions exist in a state of thermodynamic equilibrium, whereas macroemulsions are metastable systems which are only kinetically stabilized by the presence of surface-active agents slowing coalescence. The inner structure of microemulsions can be a droplet-type (o/w and w/o) microemulsion or a bicontinuous (Lee et al., 1990; Krishnan et al., 2002; Burauer et al., 2003; Ciach and Poniewierski, 1994). The bicontinuous structure of microemulsions is described as coexisting and mutually inter-twinned continuous water and oil with large amounts of surfactant (Burauer et al., 2003) or an accumulation of swollen micelles, which are so numerous that they touch one another (Salager et al., 2005).
The phase behavior of microemulsion systems consisting of oil, water and non-ionic surfactants can lead to emulsions with unique properties: by adjusting temperature and composition a system with three liquid phases is obtained. These systems can be used as solvent systems for reactions such as the hydroformylation of long-chained olefins. Knowledge of the occurring dispersion and coalescence processes is crucial for process optimization and control. Using an endoscope measurement technique in a stirred tank, relevant criteria that determine the formation of complex droplets by the two dispersed phases such as multiple emulsions are defined. The influence of the third phase on dispersion and coalescence is discussed by analyzing the drop sizes of the dispersed phases in agitated systems in situ. Furthermore, the impact of the third liquid phase on the slope of sedimentation and coalescence curves is analyzed in subsequent phase separation experiments.
Structure, interfacial film properties, and thermal fluctuations of microemulsions as seen by scattering experiments
2017, Advances in Colloid and Interface Science
Citation Excerpt :
Using optical methods and in particular ellipsometry, they succeeded in first experimental estimations of κ. A year later, the Gaussian bending modulus was also deduced from ellipsometry [104], and in 1991 and 1992 D. Langevin published overviews [38,105] where she summarized the physical properties of microemulsions, for droplets and bicontinuous phases, paying specifically attention to the Gaussian modulus. In particular, she linked recently acquired knowledge on bending moduli with structure formation: Too stiff monolayers leading to too high persistence lengths privilege the formation of lamellar (liquid crystalline) phases, whereas too floppy monolayers induce molecular mixtures.
The physics of microemulsions and in particular Dominique Langevin's contributions to the understanding of microemulsion structure and bending properties using scattering techniques are reviewed. Among the many methods used by her and her co-workers, we particularly emphasize optical techniques and small angle neutron scattering (SANS), but also neutron spin echo spectroscopy (NSE). The review is then extended to more recent studies of properties of microemulsions close to surfaces, using reflectometry and grazing-incidence small angle neutron scattering (GISANS).
Influence of dispersion conditions on phase separation in liquid multiphase systems
2017, Chemical Engineering Science
The phase separation of liquid/liquid systems consisting of oil, water and amphiphilic molecules is a function of temperature and composition. The phase separation is fastest in liquid three phase systems, where the organic and aqueous excess phases are separated by a microemulsion middle phase. In this work, a detailed analysis of the relevant physical properties (density, rheology, interfacial tension) of the phases in combination with drop size distribution measurements and image analysis of the droplet interactions is performed using an endoscope measurement system. This methodology enables to directly quantify influencing effects of droplet size and droplet interactions on dispersion and phase separation processes. The duration and character of the separation process strongly depends on the droplet interactions (e.g. formation of multiple emulsions) of the dispersed phases.
The Laplace equation of capillarity
1998, Studies in Interface Science
The chapter surveys the historical developments that led to the original explanation of the connection between interfacial bending and the pressure jump across a surface. It provides a detailed account of the surface excess concept and its role in the proper definition of a dividing surface fundamental equation. It formulates the basic variational problem that characterizes all capillary systems and discusses the important role of the free energy formulation in capillary variational problems. The chapter surveys alternative curvature measures and contrasts the form of alternative curvature measures with the attempts by Gibbs and other workers to develop a non-moderately curved capillary theory with a corresponding generalization of the classical Laplace equation of capillarity. It provides a generalization of the classical Young–Laplace equation that is completely second-order in the principal curvatures and also provides numerical examples of the influence of first-order bending energy effects upon the shape of axisymmetric pendant or sessile drops.
Near-critical liquid/liquid interfaces of simple and complex mixtures probed by ellipsometry
1997, Physica A: Statistical Mechanics and its Applications
Measurements of the coefficient of ellipticity $ϱ$ of light reflected at liquid/liquid interfaces of five binary mixtures are presented and analyzed in terms of theories which account for the interfacial thickness on the basis of the intrinsic profile and capillary waves. For simple mixtures of organic compounds exhibiting a lower miscibility gap and aqueous systems of weak amphiphiles like oxyethylene butylether (n-C₄E₁ and i-C₄E₁) with an upper miscibility gap, the experimental results for $ϱ$ are consistent with current composite theories of the interfacial thickness. However, for an aqueous system of a strong amphiphile (C₁₀E₄, a nonionic surfactant) the results for $ϱ$ deviate significantly from the calculated values at temperature |T − T_c| > 2 K. This is attributed tentatively to the formation of a layer of surfactant in the interface of this water-continuous system.
Differential geometric theory of capillarity
1996, Colloids and Surfaces A: Physicochemical and Engineering Aspects
Interfacial physics is a rich area of study with many practical manifestations and significant complexity inherent in the underlying two-dimensional behaviour. For example, structures formed from aggregates of self-assembled amphiphiles may show a variety of forms and properties ranging from ordered arrays of micelles to disordered, bicontinuous microemulsions. Any theoretical study of this behaviour must begin with a characterization of both the shape and energetic state of the interface. Often one has terms in the energy that depend on both the area (e.g. surface tension) and the curvature. We present a review of the various “curvature measures” that have historically been employed to evaluate the degree of surface bending, and their relationship to both the generalized theory of capillarity and the form of the corresponding equilibrium conditions (e.g. the Young-Laplace equation of capillarity).

View all citing articles on Scopus

¹: Author to whom correspondence should be addressed.

View full text

Relationship between microemulsion structure and surfactant layer bending elasticity

Abstract

J. Phys. Chem.

Accounts Chem. Res.

Phys. Rev. Lett.

Z. Naturforsch.

J. Phys. (Paris)

J. Chem. Phys.

J. Phys. (Paris)

Phys. Rev. Lett.

Phys. Rev. Lett.

J. Chem. Phys.

Phys. Rev. A