Surfactant fluorescence in the study of aggregation and clouding

The intrinsic fluorescence of Triton X-114 and Igepal CO-630 was used to monitor the aggregation behavior of micellar solutions of these surfactants. The response to changes in surfactant concentration, increases in temperature up to and beyond the cloud point, and addition of an ionic surfactant (SDS) was monitored. The intrinsic fluorescence was used to measure aggregate anisotropy as a function of SDS concentration and temperature. Relative aggregate abundance showed a minimum at the CMC, confirming the existence of premicellar assemblies. Structural differences in the hydrophobic portions of the two nonionic surfactants led to vastly different packing in their aggregates. The addition of SDS produced smaller, more closely packed micelles.