Interaction between Cetyltrimetylammonium Tosylate and Two Poly(oxyethylene)–Poly(oxypropylene)–Poly(oxyethylene) Block Copolymers Studied by Cyclic Voltammetry

Abstract

Mixtures of hexadecyltrimetylammonium tosylate (hexadecyltrimethylammonium p-toluene sulfonate or cetyltrimethylammonium tosylate, CTAT) with two Pluronic block copolymers, F127 and F68, were studied using cyclic voltammetry. The hydrodynamic radii of aggregates were analyzed in light of the aggregate composition. It was confirmed that the mixtures CTAT-F127 and CTAT-F68 have different behaviors. This corroborates that the interaction between different Pluronics and the same conventional surfactant depends on the kind of copolymer surfactant and also that differences in the size of the hydrophobic and the hydrophilic parts of the molecule may cause different behaviors. The penetration of CTAT into the micelle core may be more or less hindered by the size and structure of the hydrophilic shell. However, once the conventional surfactant has penetrated the corona and reached the polyoxypropylene core in a cooperative manner, the aggregates tend to disappear, thus being replaced by smaller structures, which are probably complexes having a finite number of CTAT molecules per copolymer molecule.