Phase structure, nuclear magnetic resonance and rheological properties of viscoelastic sodium dodecyl sulphate and trimethylammonium bromide mixtures

Abstract

The phase diagram of octyltrimethylammonium bromide and sodium dodecyl sulphate (SDS) in water ( > 90 %) is reported at 298 K; the phase regions observed are liquid, two liquid, and liquid plus liquid crystal. Liquids with viscoelastic properties occur close to the SDS rich liquid boundary, and a correlation is observed between the surfactant n.m.r. linewidths and the rheological properties of these liquids. The most likely explanation of these effects is one involving the occurrence of both cylindrical and spherical micelles, but the possibility that the viscoelasticity is due to the presence of a microemulsion can not be excluded.