THE FORMING EQUATION FOR THE LAMELLAR LIQUID CRYSTAL

The conductances of sodium perfluorooctanoate (SPFO), sodium dodecylsulphate (SDS), dodecyltr imethylammonium bromide (DTAB), and tetradecyltrimethylammonium bromide (TTAB) in 18crown-6 ether + water (CR+W), beta-cyclodextrin + water (CYC+W), and 1,10-phenanthroline + water (Phen+W) mixtures with fixed 4 mM of each additive were determined over the temperature range of 5-55 degreeC. The conductivity plots for all the surfactants showed single break from which the critical micellization concentration (cmc) and degree of micelle ionization (X) were computed. From the pre and the post micellar slopes of the conductivity curves, the equivalent conductivities of the monomeric (lambdal ass) and the micellar states (lambdal mic), respectively, were calculated and discussed with respect to the surfactant-additive complexation. It was observed that the micelle formation of all the ionic surfactants irrespective of the nature of their head groups were delayed in CYC+W in comparison to that in CR+W and Phen+W systems over the temperature range studied. The micelle formation of SPFO and SDS in CR+W and Phen+W systems showed stabilization of the respective micelles due to the adsorption of Na^+-CR and Na^+ -Phen complexes at the micelle solution interface in comparison to that of DTAB and TTAB.