Micelle Formation by Anionic and Cationic Surfactants in 18-Crown-6 Ether + β-Cyclodextrin + Water Systems

The conductances of sodium decyl sulfate (SDeS), sodium dodecyl sulfate (SDS), dodecyltrimethylammonium bromide (DTAB), and trimethyltetradecylammonium bromide (TTAB) have been determined in 18-crown-6 ether + water (CR + W), β-cyclodextrin + W (CYC + W), and in CR + CYC + W mixtures with fixed 0.0151 mol dm−3 of CR and varying the amount of CYC with the overall change in the mole–fraction range of CYC from 0.0 to 0.5 in a CR + CYC + W mixture at 30 °C. From the conductivity data, the critical micellar concentration (cmc), degree of counter ion dissociation (β), free energy of transfer of the surfactant hydrocarbon chain from medium to the micelle (), and free energy of transfer of surface contributions () of SDS, SDeS, DTAB, and TTAB have been computed. It has been found that the micelles of anionic surfactants are stabilized in a CR + W mixture in comparison to that in pure water, whereas micelles of cationic surfactants remain more or less unaffected. Micelles of all of the above surfactants are denatured as the amount of CYC is increased in the CR + CYC + W mixture. The effect of denaturisation is stronger on the micelles of SDS and TTAB in comparison to that of SDeS and DTAB, respectively.