Direct Visualization of Mesh Structures at Solid/Solution Interfaces by Atomic Force Microscopy

Abstract

The formation of adsorbed surfactant layers consisting of a mesh or network of branched cylindrical aggregates on muscovite mica by several surfactant systems is described. The curvature of the adsorbed aggregates is varied by a variety of mechanisms that all generate morphologies between adsorbed cylinders and bilayers, and the resulting lateral structure is imaged by "soft contact" atomic force microscopy. We compare the direct images and Fourier transforms of the adsorbed layer structures, and relate them to those formed in bulk solution.

Laterally nanostructured adsorbed layers of surfactant/surfmer mixtures before and after polymerisation

“…3 shows 95 nm × 95 nm AFM deflection images of the transformation of cylindrical structure of DTAB (2 cmc) into a bilayer with increasing proportion of MEDDAB. As expected from studies of DDAB/DTAB mixed films [24], increasing the proportion of a surfactant with a spontaneous curvature favouring planar structures results in a reduction in the net curvature of the mixed film. The cylindrical morphology favoured by DTAB persists to a 21:79 MEDDAB:DTAB bulk composition.…”

“…A wealth of AFM studies of surfactant self-assembly on various substrates have revealed the existence of globular [20], cylindrical [16,17], mesh [24,25] and bilayer [17,26] structures. The effects of factors such as alkyl chain length [15], headgroup structure and charge [18,20], counterion type [20] and electrolyte concentration [27,28] all been found to mirror the structural trends observed in bulk self-assembly.…”

Adsorption of hexyl--bis(dodecyldimethylammonium bromide) gemini surfactant on silica and its effect on wettability

“…Then, a jump-in process happens following the maximum force. The long-range repulsive force is typical for the study of the adsorption of cationic surfactants at solid-solution interface and the repulsion is believed to give information on the structures of the adsorbed surfactant aggregates [14]. In the present system, the long-range repulsive force is suspected to indicate the presence of C 12 C 6 C 12 Br 2 bilayer aggregates at the solidsolution interface.…”

“…Differently, for the adsorption of the traditional single-chain surfactant, the wormlike micelles or hemimicelles were always found at the solid-solution interfaces by the in situ AFM imaging [10,12,14,19]. This may be attributed to the different molecular nature of the single-chain surfactants and the gemini surfactants.…”

“…It has crucial applications in diverse fields such as detergency, mineral flotation, lubrication, corrosion inhibition, tertiary oil recovery and so on. Over the last few decades, different methods [1][2][3][4][5][6][7][8] have been used to carry out the study of surfactant adsorption at the solid-solution interface [9][10][11][12][13][14][15][16][17] and valuable results have been obtained [18][19][20][21][22][23][24][25][26][27][28][29]. The influence of surfactants on the wettability of solid surfaces has also been studied extensively [30][31][32][33][34][35][36].…”