Molecular conformations in surfactant micelles

For more than half a century, the cornerstone to our understanding of molecular organization in amphiphilic aggregates has been Langmuir's principle of differential solubility¹, according to which the polar heads of amphiphilic molecules dissolve in water whereas the hydrocarbon tails cluster in a core in order to minimize solvent contact2-5. This view has recently been challenged; much spectroscopic data6-17 have been construed11-17 to indicate significant penetration of water into the cores of micelles. Here various models of micellar structure are critically tested against results from NMR and recent small-angle neutron scattering (SANS) experiments. Molecular organization is found to be the consequence of Langmuir's principle and of the packing requirements imposed by steric constraints among chain molecules at interfaces. The evidence is unambiguous that these cores are virtually devoid of internal water.