Micelle formation by sodium dodecylsulphate and dodecyltrimethylammonium bromide in water - amino acid systems

Abstract

The conductances of sodium dodecyl sulphate (SDS) and dodecyltrimethylammonium bromide (DT AS) have been determined in water in the presence of various amino acids, such as glycine (Gly), alanine (Ala), valine (Val) and methionine (Meth) at 30&deg; C. From the conductivity data, the critical micellar concentration (cmc), degree of counter-ion dissociation (&beta;), free energy of transfer of the surfactant hydrocarbon chain from medium to the micelle (&Delta;<em>G</em>^o_HI&rsquo;) and free energy of transfer of surface contributions (&Delta;<em>G_s</em>^o) have been computed. It has been found that inspite of the opposite nature of SDS (anionic) from that of DTAB (cationic),the additive effect of Ala and Meth is almost similar on the micellisation of both the surfactants. However. it is much more pronounced in the case of DTAB.