Cholesteric, Smectic, and Ferroelectric Liquid Crystals

Summary

The physical properties of cholesteric liquid crystals (CLCs) are similar to nematics except that the director axis assumes a helical form with a finite pitch p = 2π/q₀. This chapter summarizes some basic physical properties associated with the helical structure. The evolution of a cholesteric to a nematic liquid crystal may be viewed as the "untwisting" of the helical structure. Most treatments of optical properties of a CLC are discussed for the case where the crystal dimension is assumed to be infinite. Extensive theoretical modeling/simulations have advanced understanding such field‐induced effects and switching dynamics. Smectic liquid crystals possess a higher degree of order than nematics; they exhibit both positional and directional ordering in their molecular arrangements. The free energy of ferroelectric liquid crystals is more complicated; besides the elastic energy FE, several others play an equally important role in determining the response of the ferroelectric‐liquid crystal to an external field.