Azimuthal ordering in Langmuir monolayers

A simple mean-field model of azimuthal ordering in Langmuir monolayers induced by anisotropic dispersion forces is presented. The approach is removed from previous studies of this interaction in systems of grafted rods insofar as the tilt of amphiphiles is decoupled from azimuthal ordering and treated as an external variable. We examine the phase space of fixed tilt against temperature, finding that azimuthal ordering is second order for most tilts, except in the range 57°-66°, where it is first order. This is related to the existence of three different types of azimuthal order; polar, nematic, and polar-nematic. © 1998 American Institute of Physics.