Influence of 1,3-Butanediol on the Viscoelasticity of Surfactant Solutions

The rheological behavior of rodlike micelles in a 1,3-butanediol/water mixed solvent was investigated. The rodlike micelles were prepared by mixing sodium salicylate, with cetyltrimethylammonium bromide. When water was replaced by 1,3-butanediol, the viscosity maxima decreased drastically. The viscosity minimum, on the other hand, increased at low 1,3-butanediol contents and decreased again at higher amounts of 1,3-butanediol. As a result of the opposite changes the two maxima were replaced by a single maxima when the content of 1,3-butanediol was 15 %. The change in the viscosity was a consequence of a change in the structural relaxation times while the storage moduli remained constant. The stress relaxation was due to a reptation mechanism at maximum points while at the minimum of the viscosity the mechanism was due to a kinetic controlled mechanism.