The nonionic surfactant p-tert-octylphenoxy polyethylene (9.5) ether (TritonX-100) possesses excellent surfactant performance in detergency, emulsifying and wetting characteristics over a fairly broad temperature range and being readily biodegradable has been widely used for decades. The issue about the TX100 micelle structure, however, is not trivial because at low concentrations it is has a two-layer spherical structure with partially overlapping internal and external layers of Triton X-100 molecules and no distinct hydrophilic-hydrophobic boundary. The effect of oil addition to this structure is not easily predictable. We have studied the evolution of the micelles upon addition of linear and cyclic alkanes by dynamic light scattering, viscosimetry, PFGE-NMR and NOE-NMR. Upon oil addition, the micelles first swell but above a certain critical oil content decrease in size. Such a decrease is due to two effects: a reduction in the aggregation number, and a dehydration of the polyethylene chains.
gerardo.palazzo@uniba.it
