Neutron specular and off-specular reflection from the surface of aerosol-OT solutions above the critical micelle concentration

Abstract

Neutron reflection has been used to study the air/solution interface of bis(2ethylhexyl) sulfosuccinate-water at concentrations in the range 1-5% v/v, well above the critical micelle concentration of 0.11%. No features other than the adsorption of a monolayer are observed at a concentration of 1%, but at 2% and above peaks are observed in the specular reflectivity that correspond to a multilayer structure with a repeat distance of 175-180 A. This is most probably caused by preferential adsorption of the lamellar phase, which in this concentration range coexists with solution and has a spacing of 180 A. At the same time as the appearance of peaks in the specular reflectivity a strong peak also appears in the off-specular direction and we attribute this to conformal roughness of the multilayer structure. Such a large roughness is not caused by the actual air/water surface, but is probably a consequence of large amplitude undulations (Helfrich waves) in the bilayers constituting the lamellar structure at the interface.

Weakly charged lamellar bilayer system: Interplay between thermal undulations and electrostatic repulsion

“…Our study connects to the current experimental [10][11][12][13][14][15][16][17] and theoretical [18][19][20][21][22][23][24][25] interest in the interplay between electrostatic interactions and thermal undulations in lamellar phases, especially to the recent study of Schomäcker and Strey [14]. These authors charged the dilute lamellar phases of the non-ionic surfactant pentaethylene glycol dodecyl ether (C 12 E 5 ) by adding small amounts of ionic surfactants, and followed the evolution of the Bragg peak by backscattering of light.…”

“…The experimental data are approximately in the range 10 ≤ κD ≤ 30 for which the self-consistent field theory is expected to be valid. ξ is calculated from equations (15)(16)(17)(18). Since the charge density is very low, the calculated value for the electrostatic contribution to the bending modulus k c,el [47] is only O(0.1 k B T ), which is negligible on the scale of the experimental resolution.…”

“…On the other hand, if electrostatic interactions exist, these will compete with undulations. Unless the electrostatic interactions are highly screened by the addition of large amounts of electrolyte, one must then consider the interplay between the thermal undulations and the electrostatic interactions [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25]. 142 The European Physical Journal E The aim of the present study is to obtain quantitative data characterizing the C 10 E 3 bilayer flexibility and the impact of electrostatic interactions on the C 10 E 3 lamellar phase.…”

Lipid phase behaviour under steady state conditions

“…This generates non-equilibrium transport processes across the air-water interface, which could in 60 turn give rise to unexpected structural changes. [4][5][6][7][8] Similar conditions exist also in the lipid tear film formed on our eyes, which indeed should act to prevent evaporation and dry eyes 9 .…”

Structure and morphology of Cu/Ni film grown by electrodeposition method: A study of neutron reflectivity and AFM

“…The application of off-specular x-ray and neutron reflectivity have become widespread, including study of capillary-wave fluctuations at a liquid surface [11], partially correlated interface roughness in multilayers [8,9,10,12], laterally modulated structure of periodic gratings [13,14], morphology of diblock copolymers [15][16][17][18] and other systems [19][20][21]. Detailed understanding of in-plane morphology and roughness of interfaces of a layer system is required to understand the influence of these factors on magnetic, electric and optical properties of layered systems [22][23][24].…”