Recent advances in thermotropic liquid crystals

Liquid crystals are states of condensed matter whose symmetries lie between those of 3-dimensionally periodic crystals and isotropic liquids. Thermotr opic liquid crystalline phases are exhibited by a large number of organic c ompounds whose molecules have anisotropy of shape. A typical intermolecular energy responsible for the stability of the relevant order in the medium i s comparable to the thermal energy, and thus liquid crystals are soft mater ials. Relatively weak interactions like those between molecular dipoles or chiral centers of appropriate molecules can give rise to new types of liqui d crystals. Now more than 35 types are known, and many more are likely to b e discovered in the future, The soft nature of the medium, coupled with ani sotropic optical and dielectric properties gives rise to many electro-optic effects at relatively low voltages. These are exploited in liquid crystal displays (LCDs), which are the lowest power (similar to 1 muw/cm(2)) consum ing flat panel devices and used in all calculators, laptop and palmtop comp uters, cellphones, etc. Further, phase transitions between different types of liquid crystals, some of which are analogous to those in other materials like magnets or superconductors, offer a rich variety of problems of funda mental significance, As such, the R&D effort on liquid crystals has been gr owing steadily in the past three decades, resulting in better and cheaper d isplays as well as discoveries of new types of liquid crystals. The article gives a broad overview of the subject.