Liquid Crystals

Chapter 1 - Introduction to Liquid Crystals

1.1.   MOLECULAR STRUCTURES AND CHEMICAL COMPOSITIONS

Liquid crystals are wonderful materials. In addition to the solid crystalline and liquid
phases, liquid crystals exhibit intermediate phases where they flow like liquids,
yet possess some physical properties characteristic of crystals. Materials that
exhibit such unusual phases are often called mesogens (i.e., they are mesogenic),
and the various phases in which they could exist are termed mesophases.1,2 The
well-known and widely studied ones are thermotropics, polymerics,3 and lyotropics.
As a function of temperature, or depending on the constituents, concentration,
substituents, and so on, these liquid crystals exist in many so-called mesophases—
nematic, cholesteric, smectic, and ferroelectric. To understand the physical and
optical properties of these materials, we will begin by looking into their constituent
molecules.4