Self-assembled uniaxial and biaxial multilayer structures in chiral smectic liquid crystals frustrated between ferro- and antiferroelectricity

Abstract

With a view to obtain a molecular model for the subphases produced by the frustration between ferro- and antiferroelectricity in chiral smectic liquid crystals, we report results on two compounds and observe (i) the staircase character of uniaxial SmC?* itself in the bulk and (ii) the multipeaked characteristic reflection bands due to the modulated helical structures just above the SmCA* temperature range. We suggest the emergence of several uniaxial and biaxial subphases. The results show that both types of subphases can be specified by qT=[F]?([A]+[F]) in the zero-order approximation; [A] and [F] are the numbers of antiferroelectric and ferroelectric orderings in the unit cell. We consider the basis of both types of subphases, particularly the description of the short-pitch helical structure of SmC?* , in terms of the molecular models so far proposed and emphasize the important role played by the discrete flexoelectric polarization.