Thermotropic crystal

A liquid crystal (LC) is thermotropic if the order of its components is determined or changed by temperature.

If temperature is too high, the rise in energy and therefore in motion of the components will induce a phase transition: the LC will become an isotropic liquid. If, on the contrary, temperature is too low to support a thermotropic phase, the LC will change to glass phase.

There is therefore a range of temperatures at which we observe thermotropic LCs; and most of these have several "subphases" (nematic, smectic...), which we may observe by modifying the temperature.