Temperature Dependence of the Intrinsic Pitch in Induced Cholesteric Systems

Abstract

AbstractBased on the molecular‐statistical theory of Goossens a model has been developed to explain the temperature dependence of the intrinsic pitch in cholesteric systems induced in nematic host phases by chiral guest molecules. In the case of a rotational symmetric distribution function around the long axis of the chiral molecule the helix inducing dipole‐quadrupole interaction forces level out. Consequently, only a hindered long‐axis rotation causes the helical structure whose pitch increases with increasing temperature. The theoretically predicted value of the relative temperature gradient of reciprocal pitch 1/p−1(dp−1/dT) are in good agreement with the presented experimental data. The influence of structure of the chiral guest molecules on the helical twisting power as well as that of the nematic host phases also can be understood in terms of the proposed model.