  The tendency of amphiphilic molecules to form micelles in aqueous solution is
a consequence of the hydrophobic effect. The fundamental difference between
micelle assembly and macroscopic phase separation is the stoichiometric
constraint that frustrates the demixing of polar and hydrophobic groups. We
present a theory for micelle assembly that combines the account of this
constraint with a description of the hydrophobic driving force. The latter
arises from the length scale dependence of aqueous solvation. The theoretical
predictions for temperature dependence and surfactant chain length dependence
of critical micelle concentrations for nonionic surfactants agree favorably
with experiment.
