Pitch–concentration relationships in multicomponent liquid crystal mixtures

The variation of helical pitch in multicomponent liquid crystal mixtures is derived using the concept of the long-range distortions induced by chiral molecules in a nematic matrix. The pitch in a mixture is a quadratic function of the number densities of component molecules of given molecular twisting powers. The pitch variation becomes a linear function of number densities only when the twisting powers satisfy certain special conditions. The nonlinear pitch relation formulated herein is shown to describe typical experimental data on nematic–cholesteric mixtures and allows determination of experimental values of the molecular twisting power.