SIMPLE MOLECULAR-MODEL FOR INDUCED CHOLESTERIC PHASES

A phenomenological theory for the cholesteric phase induced by a chira l solute in a nematic solvent is derived from (i) the continuum repres entation of twist deformation of the nematic solvent, and (ii) the sur face anchoring energy approximation for the interactions between the s olvent and a solute of given shape. This allows a simple explanation o f the stabilization of the solvent twist deformation by the interactio ns with chiral solute. A straightforward statistical elaboration leads to the well known inverse proportionality between the pitch of the ch olesteric phase and the solute concentration. The corresponding propor tionality coefficient, i.e., the twisting power of the solute, is then related to the asymmetry of the solute shape through a chirality orde r parameter.