Light scattering and fluorescence probe studies on micellar properties of Triton X-100 in KCl solutions

The effect of KCl on micelle formation and structure of Triton X-100 (TX-10 0) was investigated by using combined static and dynamic light scattering m easurements, together with the fluorescence probe technique. An analysis of the light scattering data, including hydrodynamic radius and micellar aggr egation number, accounted for both micelle growth and hydration. Fluorescen ce studies using pyrene as a probe were carried out to determine the critic al micelle concentration (CMC) as a function of solution composition. In ad dition, with the aim of gaining information on the possible changes in the micro-environmental properties of TX-100 micelles, fluorescence probe studi es, including intermolecular pyrene excimer formation and fluorescence pola rization of coumarin 6 associated with micelles, were carried out. It was f ound that the addition of electrolyte induces a decrease in the CMC and an increase in both aggregation number and hydration. However, complementary d ata of partial specific volume and cloud point of the surfactant suggested that the main contribution to micellar hydration is due to water mechanical ly trapped in the micelle. Fluorescence measurements do not indicate change s in the micellar micropolarity, probably due to modifications of the solub ilization site of the probe caused by the micellar growth. Both pyrene exci mer formation and fluorescence polarization of coumarin 6 revealed an incre ase in microviscosity with electrolyte addition, which is consistent with i ncreased micellar hydration.