Cover Picture: On the Origin of the “Giant” Electroclinic Effect in a “De Vries”‐Type Ferroelectric Liquid Crystal Material for Chirality Sensing Applications (ChemPhysChem 6/2009)

The cover picture shows characteristics of a new ‘de Vries’‐type ferroelectric liquid crystal in which the ferroelectric transition is an order–disorder transition where the directions of molecular tilt inside a smectic layer order into a certain direction. Since the rod‐like molecules (drawn as cylinders) are tilted in the paraelectric SmA* (with random tilt directions) as well as in the ferroelectric SmC* phase, the ferroelectric transition is connected with a rather weak contraction of the smectic layer thickness (even though the optical tilt θ reaches values of about 25°). On page 890, F. Giesselmann et al. show that this new ferroelectric material exhibits a remarkably weak temperature dependence of its giant electroclinic effect (the coupling between tilt and elelctric field) in the SmA* phase. The origin of this striking electroclinic effect is the co‐occurrence of a ‘de Vries’‐type ordering with a weak first‐order tilting transition.