Simple molecular model for induced cholesteric phases

A phenomenological theory for the cholesteric phase induced by a chiral solute in a nematic solvent is derived from (i) the continuum representation of twist deformation of the nematic solvent, and (ii) the surface anchoring energy approximation for the interactions between the solvent and a solute of given shape. This allows a simple explanation of the stabilization of the solvent twist deformation by the interactions with chiral solute. A straightforward statistical elaboration leads to the well known inverse proportionality between the pitch of the cholesteric phase and the solute concentration. The corresponding proportionality coefficient, i.e., the twisting power of the solute, is then related to the asymmetry of the solute shape through a chirality order parameter.