Effect of Catechol on the Size and Shape of CTAB Micelles in Aqueous Solutions

Abstract

Abstract The effects of catechol on the change of cetyltrimethylammonium bromide (CTAB) micelles in aqueous solutions have been studied by Ultramicroelectrode (UME) cyclic voltammetry and Time-Resolved Fluorescence Quenching (TRFQ). It has been shown that the diffusion coefficient decreases and the micelle aggregation number increases with the addition of catechol. This indicates that catechol has influence on the size or shape of CTAB micelles. In order to analyze the change of the micelles, other micelle parameters like the effective radius (a), surface area of micelle (S), area of single CTAB molecule (A) and packing parameter (P) were calculated. The values of P which is relative to the shape of the micelles are consistent with the change of the diffusion coefficient. All the results show that catechol can accelerate the increase of the aggregate size and sphere-to-rod morphology change of CTAB micelles even with lower concentration of CTAB. This is because that hydrophobic force makes catechol insert into CTAB micelles between CTAB molecules, which leads to the increase of the radius of curvature. The increase of aggregate size and the sphere-to-rod morphology change are also promoted as a result.