On the anomalous temperature dependence of ferroelectric Sc*. liquid crystals

A biaxial elastic model for the temperature dependence of S_c* helical pitch is proposed on the basis of a phenomenological theory of S_c* liquid crystals accompanied by a biaxial molecular ordering playing an important role for the anomalous behaviour of the helical pitch near the S_c*-S_A transition point. In the S_c*. phase of p-(n-decyloxybenzylidene)-p-amino-(2-methylbuthyl)-cinnamate (DOBAMBC), a qualitative agreement with the observed helical pitch is found by choosing a few material parameters concerned with a biaxial elasticity and an anisotropy of the elastic constants.