Shape changes of C16TABr micelles on benzene solubilization

The microstructure of C(16)TABr micelles with solubilized benzene was investigated by field-dependent H-2 NMR spin relaxation of C(16)TABr-Alpha-d(2). The relaxation data, supported by cryogenic transmission electron microscopy that excludes oblate micelle shapes, suggest that the C(16)TABr micelles, slightly elongated even without benzene, become longer and more polydisperse on benzene addition. Field-dependent H-2 spin relaxation measurements on the benzene C6D6 indicate that at low solubilizate content the benzene is predominantly located at the micellar interface, reorients more slowly than in bulk, and has a high lateral diffusion coefficient. Above a particular benzene concentration, the surfactant relaxation data suggest no further elongation but a radial growth, while the benzene relaxation shows that a large part of the benzene is residing in an interior region with near-bulk characteristics: the micelles become slightly elongated microemulsion droplets.