Study of the Lyotropic System Sodium Dodecyl Sulfate (SDS) / Decanol / Heavy Water

Abstract

Measurements of optical refractive indices (ordinary and extraordinary), as a function of temperature, are reported for the heavy water / SDS molar ratio Mw = 36, with a decanol / SDS molar ratio Md = 0.324. The nematic biaxial phase emerges from the crystal phase (which occurs below 18°C) into a coexistence region with two uniaxial nematic phases (discotic ND and cylindrical NC) , before entrance in the NC phase. The transitions are discontinuous, and the biaxial phase differs from the coexistence region ND + NC . Results indicate changes of the micellar object with temperature, and at the phase transitions.