Formation of the lamellar phase of alkyl-benzenesulphonates from surfactant/water/electrolyte solutions

Abstract

In the phase diagram of sodium 1′-(4)-alkylbenzenesulfonate (4SDBS)/water/Mg(NO3)2 in the diluted surfactant regime, the appearance of three regions exhibiting various micro-structures of isotropic phases is shown. The visualization of the dynamics of the lamellar phase formation from the saturated viscous isotropic surfactant/electrolyte solution was done by the light microscopy operated with differential interference contrast (DIC) using video camera. The first stages of the liquid crystalline nucleation presented the spontaneous transition from the saturated isotropic solution to the bilayer structures. The formation of bilayer cylinders, flat lamellar, and bent lamellar phases have been found. In the biphasic isotropic + lamellar region, a growth of the lamellar microtubuli into cylinders from the viscous isotropic phase, and afterwards the distortion of the cylinders into cones, has been observed as a spontaneous nucleation process, if the isotropic solution taken over the lamellar phase has been kept between microscopic object and cover glass at room temperature.