What are liquid crystals?

Liquid crystal refers to a phase of matter that is in some ways like a liquid and in other ways like a solid (crystal). A material that exhibits such a phase is called a liquid-crystal compound or liquid crystal for short. To better understand this idea, it can be helpful to first define “liquid” and “crystal.”

§ In the liquid phase, the molecules are free to move and rotate. We say that a liquid lacks positional order and orientational order. Click Here to see a cartoon depicting this idea.

§ In the crystal phase, the molecules are located at specific places and are aligned in a particular direction. We say that a crystal has both positional order and orientational order. Click Here to see a cartoon depicting this idea.

§ In a liquid-crystal phase, the molecules will have some positional order and orientational order. There are many different known ways for this to occur. One such way is called the nematic phase. Click Here to see a cartoon depicting the nematic phase. Another way is the called the smectic-A phase. Click Here to see a cartoon depicting the smectic-A phase.