Measurement of the Gaussian curvature of the surfactant film in an isometric bicontinuous one-phase microemulsion

Abstract

Small-angle x-ray and neutron-scattering ͑SAXS and SANS͒ measurements are made of a three-component isometric microemulsion, C 10 E 4 -D 2 O-octane, in the one-phase channel around the hydrophile-lipophile balance temperature of the system. A previous SANS contrast variation experiment indicated that the microstructure of this isometric microemulsion is bicontinuous in water and oil, with the surfactant film having a zero mean curvature. We analyze the SAXS and SANS data taken with a bulk contrast in terms of a modified Berk's random wave model. We choose a spectral function which is an inverse sixth-order polynomial, with three parameters a, b, and c, as introduced by Lee and Chen earlier. This three-parameter spectral function is then used in conjunction with Cahn's clipping scheme to obtain the Debye correlation function for the microemulsion. The analysis gives an excellent agreement with the intensity data in an absolute scale. We then use the three parameters so obtained to calculate the mean Gaussian curvature of the surfactant film. We also show a three-dimensional-reconstructed morphology of the microemulsion.

Columnar and lamellar phases in attractive colloidal systems

“…A realistic framework for the modelization of these systems is represented by DLVO interaction potentials [16], which combine short-range attractions and long-range repulsions. A suited choice of DLVO models has in fact allowed to reproduce, by means of molecular dynamics calculations, many experimental observations, like the cluster phase and the gel-like slow dynamics [13][14][15].On the other hand, competing interactions have been studied in many other systems, ranging from spin systems to aqueous surfactants or mixtures of block copolymers, and often lead to pattern formation or to the creation of periodic phases [17][18][19][20][21][22][23].In this paper, we simulate by molecular dynamics a system composed of monodisperse particles, interacting with a short range attraction and a long range repulsion in analogy with DLVO models, for a large range of temperatures and volume fractions. At low temperature, increasing the volume fraction in the region of phase space where the system forms a percolating network and waiting long enough, we observe that the system spontaneously orders, to form a periodic structure composed by parallel columns of particles.…”

“…On the other hand, competing interactions have been studied in many other systems, ranging from spin systems to aqueous surfactants or mixtures of block copolymers, and often lead to pattern formation or to the creation of periodic phases [17][18][19][20][21][22][23].…”

Construction of Representative Pore Morphologies in Disordered Nanoporous Two-Phase Materials

“…While some progress has been made in producing real-space morphology or microstructure from SAXS or SANS data on two-phase systems, these analyses are complicated [13,14], involving Monte Carlo methods, or are limited to the isometric case (equal phase volume fractions) [6][7][8][9]. Electron microscopies can also be useful for directly determining the morphology of nanoscale heterogeneous materials, but the interpretation of microscopy images is often difficult [15] (due, for example, to limitations in resolution or artifacts created in sample preparation).…”

“…Two-phase materials with heterogeneities in the nm size scale are often characterized with small angle X-ray and neutron scattering (SAXS and SANS, respectively) [7][8][9][10][11][12]. These methods provide valuable information, but are not often analyzed to obtain a real space model of the morphology, since this is difficult and may not yield unique results.…”

“…For heterogeneous materials, a model of the real-space morphology or microstructure is highly desirable, since this allows a better understanding and prediction of the materials properties [1][2][3][4][5][6][7][8][9][10][11][12]. Two-phase materials with heterogeneities in the nm size scale are often characterized with small angle X-ray and neutron scattering (SAXS and SANS, respectively) [7][8][9][10][11][12].…”