Hydrodynamic and clouding behavior of Triton X-100+SDS mixed micellar systems in the presence of sodium chloride

Surface tension, cloud point, viscosity, dye solublization, and dynamic light scattering (DLS) results on aqueous micellar solutions of nonionic surfactant Triton X-100 (TX-100) and anionic surfactant sodium dodecyl sulfate (SDS) in the absence and presence of NaCl are reported. Changes in the critical micelle concentration (CMC) with the composition of the two surfactants so determined were analyzed by applying Rubingh's regular solution theory to obtain the interaction parameter beta (-3.81) showing synergism. The cloud point (CP) of TX-100 solution decreases linearly with NaCl concentration up to 1.0 M but no substantial growth in micelles was observed. On the other hand, addition of a small amount of SDS in TX-100 solution raised the cloud point above 100 degrees C. In the presence of lower NaCl concentration, TX-100 shows an initial decrease in CP followed by rapid increase. While at higher NaCl concentrations minima shift to higher concentration and no sharp increased in CP was observed. Here results are discussed in terms of dehydration of polyoxyethylene chain of TX-100 by NaCl, formation of charged mixed micelles of TX-100+SDS in water, and the screening effect by the NaCl in the mixed micellar solutions. Results are well supported by viscosity, dye solublization, and DLS measurements. Aggregation number was calculated theoretically by applying the Tenford formula.