Optical rotatory power in tilted smectic phases

Abstract

Optical Rotatory Power measurements have been done on different chiral tilted smectics which lead to reproducible results. The high-temperature uniaxial SmA and SmC * α phases do not show any ORP due to the lack of in-plane anisotropy at the mesoscopic level (i.e. a few layers). At lower temperature one gets the synclinic C * and the anticlinic C * A phases with a helical precession around the layer normal which is right-handed for C * and left-handed for C * A . These phases are separated in a finite temperature range by a set of two so-called "ferrielectrics" SmC * Fi1 and SmC * Fi2 , which are not necessarily new phases, between which the handedness changes sign at a given temperature, while the change from synclinic to anticlinic tilt angle organization is spread out over the "ferrielectric" temperature range. In order to reconcile all experimental observations, otherwise apparently incompatible, it is proposed that the "ferrielectric" region is a diphasic one where the in-plane organization changes smoothly from the synclinic type to the anticlinic one.

Dielectric Relaxation in Liquid Crystal Phases with Polar Order

“…The composition of this mixture depends on temperature and the thermal history of the sample. Similar hypotheses have already appeared in the literature [26,[28][29][30]. In our earlier work we observed the coexistence of ferroelectric and antiferroelectric phases directly in polarized light [30].…”

Continuum theory of tilted chiral smectic phases

“…The figures show that the cost in twist energy of the lock-in will be reduced if the Sm-C * rotates in the same direction as the Sm-C * α while the Sm-C * A has to take the opposite sense. This illustrates the general trend observed in the experiments [39] that the sense of the helix is opposite in the two phases for a given compound. We have thus shown that the would-be Sm-C * α phase exercises a kind of torque on the azimuthal angle Φ 0 with a non trivial sign.…”

Extension of the Hamaneh-Taylor model using the macroscopic polarization for the description of chiral smectic liquid crystals

“…Some of these phases may be missing when varying the chemical formula (tail length) [6] but the order of appearance is con-served. Two of them present a macroscopic polarization, four of them a long pitch helical precession with a sign change in the middle of the sequence [7,8,9]. Although most of these phases present a biaxiality of the unit cell, the global structure is uniaxial because of the helical precession around the layer normal and an optical activity that can be huge results from the rotation of the biaxial structure [10].…”