Dielectric relaxation process of a partially unwound helical structure in ferroelectric liquid crystals

Correlation between alignment geometries and memory effect in a surface-stabilized ferroelectric liquid crystal

Memory effect in weakly aligned surface stabilized ferroelectric liquid crystal (SSFLC) material has been investigated by electro-optical and dielectric spectroscopy in three configurations of alignment: antiparallel, 90^{∘} twisted, and unaligned planar samples. It has been observed that two types of molecular dynamics exist in antiparallel rubbed cell in which memory effect is observed for longer duration than in other samples. One dielectric relaxation process is near the surface of the electrode and a second is in the bulk of the SSFLC. Both the molecular dynamics contribute in the switching process and affect the memory phenomenon in surface stabilized geometries. However, a single dielectric process is observed in twisted geometry in which the sample is showing shorter memory effect than in antiparallel and this is compared with unaligned samples also having cell thickness less than the pitch value of FLC. In an unaligned sample, a single dielectric process is observed and the smaple does not show memory effect at all. The investigation is significant to understand the anomalies occurring in memory observations in various geometries.

Collective dielectric processes at the transition temperature of the Sm-C^{*} and Sm-A^{*} phase in a ferroelectric liquid crystal

An anomalous dielectric relaxation process, called the partially unwound helical mode (p-UHM), is a collective dielectric process apart from the well known Goldstone and soft mode process; it is studied in the smectic C^{*} (Sm-C^{*}) phase and at the transition temperature of the Sm-C^{*}-Sm-A^{*} phase in the ferroelectric liquid crystal (FLC) material. To avoid the surface effect, a thick cell of 40 μm thickness was prepared with highly rubbed surfaces of the ITO substrates. It has been observed that the dielectric properties in Sm-C^{*} and at the T_{c} temperature are dominated by the p-UHM process which is dependent on an applied oscillating field in the Sm-C^{*} phase. The probing ac and dc bias field dependences of all these collective dielectric processes have been reported in the Sm-C^{*} and Sm-A^{*} phases of FLC materials.

The effect of dopant chirality on the properties of self-assembling materials with a ferroelectric order

The first example of hockey-stick compounds exhibiting a smectic I phase with a direct transition to the isotropic phase.