Page "Liquid crystal" Paragraph 54

Thermotropic mesophases are detected and characterized by two major methods, the original method was use of thermal optical microscopy, in which a small sample of the material was placed between two crossed polarizers ; the sample was then heated and cooled.

As the isotropic phase would not significantly affect the polarization of the light, it would appear very dark, whereas the crystal and liquid crystal phases will both polarize the light in a uniform way, leading to brightness and color gradients.

This method allows for the characterization of the particular phase, as the different phases are defined by their particular order, which must be observed.

The second method, Differential Scanning Calorimetry ( DSC ), allows for more precise determination of phase transitions and transition enthalpies.

In DSC, a small sample is heated in a way that generates a very precise change in temperature with respect to time.

During phase transitions, the heat flow required to maintain this heating or cooling rate will change.

These changes can be observed and attributed to various phase transitions, such as key liquid crystal transitions.