Electro-optic and dielectric properties of polymer networks stabilised short pitch chiral smectic C* liquid crystal

ABSTRACT

We present the effect of polymer network on the ferroelectric phase for a polymer stabilised ferroelectric liquid crystal (PSFLC) system. The ferroelectric liquid crystal (FLC) exhibits a very short helical pitch, large tilt angle and relatively high spontaneous polarisation. Electro-optic and dielectric investigations are performed on films with various polymer concentrations. Measurements in the chiral smectic C* (SmC*) phase of the tilt angle and spontaneous polarisation as a function of electric field strength and polymer concentrations were performed. For low electric fields, a deformed helix ferroelectric (DHF) process was observed for pure FLC as well as for the PSFLC films, showing a linear response of the helical structure to electric field. The influence of the polymer network on the FLC properties is also investigated by linear dielectric measurements. Particularly the Goldstone relaxation mechanism. The results reveal a gradual decrease of the dielectric strength with an increase in the network density. However, the relaxation frequency of this mechanism seems to be insensitive to the polymer network density. These behaviours were interpreted by the increase of both the effective elasticity and the rotational viscosity of the SmC* when stabilised by the polymer network.

Graphical abstract

KEYWORDS:

• Ferroelectric liquid crystals
• polymer liquid crystals
• deformed helix ferroelectric effect
• electro-optic properties
• dielectric relaxation

Disclosure statement

No potential conflict of interest was reported by the author(s).