ABSTRACT

Mesophases are found in all kinds of materials. To specify the nature of the mesogenic material one distinguishes between:

1.Thermotropic LCs (low molecular mass species) 2.Lyotropic LCs (aqueous solutions of amphiphiles) 3.Polymeric LCs (reticulated or not) 4.Colloidal LCs (suspensions of colloidal particles, the best known being the tobacco mosaic virus)

This distinction is important because, even though a mesophase always has, by definition, the same symmetries and the same laws of macroscopic behavior, its physical constants strongly depend on the chosen material. Thus, thermotropic nematics flow very easily (with viscosities ranging from that of water to that of glycerine) while polymeric (unreticulated) nematics are extremely viscous.