Memory effect near transition temperature in Sm C∗ phase in nonsurface stabilized ferroelectric liquid crystals

Abstract

Memory behavior in the ferroelectric liquid crystal ͑FLC͒ material, Felix 17/100, has been investigated by electro-optical, dielectric, and hysteresis methods at different temperatures ranging from room temperature to near ferro-paraelectric phase transition. Memory effect has been observed in the studied material near the transition temperature in Sm C ‫ء‬ phase in the cells having thickness greater than the pitch value of the material. This is in contrast to the memory effect observed in conventional FLCs where thickness of the cell has to be less than the pitch value of the material. Electrical conductivity measurements elucidate that the steep increase in the conductivity near the transition temperature in Sm C ‫ء‬ phase enhances the motion of free ions and probably weakens the depolarization field in the material, thereby showing memory effect.

Enhanced Memory Effect in Conducting Polymer Coated Surfaces of Ferroelectric Liquid Crystals

“…Therefore, the molecules remain in the memory state in deep Sm C Ã phase for the cell having P3HT coating. This is in contrast to the earlier report 22) in which the memory effect was observed only near transition temperature in non-surface stabilized FLCs and not in the deep Sm C Ã phase for rubbed polyimide surfaces of Felix 17/100. Therefore, it can be said that P3HT layers help to enhance the memory effect in Felix 17/100.…”

“…These observations confirm that there is a complete memory effect in the entire frequency range in FLC material having the layers of P3HT. The memory effect in Felix 17/100 using rubbed polyimide surfaces has been reported earlier by our group 21,22) where no memory was observed. Hence, optical response of P3HT coated surfaces of FLC material supports the memory effect observed by textural observations (Fig.…”

“…Such type of nonlinearity is due to the generation of depolarization field to reverse the direction of spontaneous polarization. 22,24) Moreover, it has been observed earlier that if the pulse width of the external voltage is larger than approximately a few hundred s, then accumulation of excess ions at the interface between the FLC medium and the alignment layer takes place. 25) These excess ions generate an external field, which increase the depolarization field by adding itself in depolarization field and such type of field is also responsible for the nonlinearity in the output response of rubbed polyimide FLC samples.…”

Scientific developments of liquid crystal-based optical memory: a review

“…Coondoo et al investigated memory behavior in an FLC material, Felix 17/100, through dielectric, electro-optical, and hysteresis methods at different temperatures ranging from room temperature to near ferro-paraelectric phase transition [86]. The authors observed a memory effect near the transition temperature in the Sm C * phase in cells having thickness greater than the pitch value of the material.…”