Alcohol-Induced Structural Transformations of Surfactant Aggregates

Abstract

Alcohol-induced structural transformations of cetyltrimethylammonium bromide (CTAB) aggregates adsorbed on mica have been investigated using atomic force microscopy (AFM). A series of alcohols of different chain lengths was used to study the effect on surface aggregate structure. In CTAB solutions of fixed concentration, increasing amounts of alcohol spread the lateral spacing of the CTAB cylinders adsorbed on mica. At high alcohol concentrations, relative to the alcohol chain length, the surface aggregates changed from a cylindrical to a spherical structure. This structural transformation is explained by hydrophobic interactions between the alcohol and surfactant micelle.

A Thermometric Titration Study on the Micelle Formation of Sodium Decyl Sulfate in Water

“…This was recently demonstrated by means of atomic force microscopy for the aggregation of sodium ndodecyl sulfate at the graphite/aqueous solution interface in the presence of n-dodecanol (17), and in a study on alcohol-induced structural transformations of cationic surfactant aggregates on mica (18). mic H was calculated from the titration curve as the height of the step function at the cmc, i.e., by taking the enthalpy difference between the two straight lines extrapolated to the cmc (Fig.…”

Effect of organic solvents on J aggregation of pseudoisocyanine dye at mica/water interfaces: Morphological transition from three-dimension to two-dimension

“…For example, addition of alcohol decreases the adsorption of CTAB and structural transition from cylinders to spheres has been found [3]. The observed transition can be best explained by hydrophobic interactions between CTAB and alcohol chains.…”

“…In particular, molecular adsorption of surfactants or dyes at the solid/liquid interface has attracted a great deal of attention because adsorbed molecules often organize themselves into aggregates on the surface of solids that can dramatically change the properties of the interface. Consequently, the structures into which organic molecules assemble in the bulk solution are different from those at the interfaces [2,3]. For example, some surfactants such as C 14 TAB (tetradecyltrimethylammonium bromide) and CTAB (cetyltrimethylammonium bromide) have been shown to form flattened cylindrical aggregates on mica in aqueous solution [4][5][6].…”

The Effect of Concentration on Lubricating Properties of Aqueous Solutions of Sodium Lauryl Sulfate and Ethoxylated Sodium Lauryl Sulfate

“…There are no thermodynamic stimuli above the CMC value which would stimulate further adsorption and the chemical potential does not change. The surface phase is fully set and formation of micelles in the bulk phase begins [25,26,[53][54][55].…”