Effect of N-Decyl-N-N-Dimethyl-3-Ammonio-1-Propanesulfonate on the Solution Properties of Sodium Dodecyl Sulfate

Conductivity measurements have been used to study the solution properties of mixtures of sodium dodecyl sulphate (SDS) and n-decyl-n,n-dimethyl-3-ammonio1- propanesulfonate (DPS) at 35 and 40 ºC and various concentrations of DPS. The critical micelle concentrations (CMCs) of the solution of SDS and its mixtures with DPS were extrapolated from the inflection points on conductivity versus concentration curves. The CMCs increased as the temperature of the solution increased but decreased with increasing concentration of DPS. The degree of ionization of the mixed micelles calculated from the slope before and after the inflection point on concentration versus conductivity plots increased with increasing concentration of DPS but decreased with temperature. These results have been fully discussed based on the effect of non-charged DPS headgroup on the charged SDS headgroup