Unusual scaling in the rheology of branched wormlike micelles formed by cetyltrimethylammonium bromide and sodium oleate.

Natural fatty acids such as sodium oleate form highly viscous supramolecular complexes with long-chain cationic surfactants through cooperative self-assembly. Here we report the rheological behavior of linear and branched wormlike micelles formed in mixtures of cetyltrimethylammonium bromide (CTAB) and sodium oleate (NaOL). Addition of sodium oleate induces an increase in the axial ratio of the mixed micelles.

Viscoelastic fluids originated from enhanced solubility of sodium laurate in cetyl trimethyl ammonium bromide micelles through cooperative self-assembly.

Sodium laurate (SL), which is otherwise sparingly soluble in water at room temperature, forms viscoelastic fluids when mixed with cationic cetyl trimethylammonium bromide (CTAB) micelles. This originates from a cooperative assembly of CTAB and SL through electrostatic interaction and the ability of the tetralkyl ammonium headgroup in decreasing the Kraft point of SL. Addition of SL to CTAB induces the formation of rod-like micelles, the length of which can be controlled by the composition of the mixture.