Mesomorphic State –

A state of matter in which the degree of molecular order is intermediate between the perfect 3D, long range positional and orientational order found in solid crystals and the absence of long range order found in isotropic liquids, gases & amorphous solids.

Cholestric Phases –

It is typically composed of nematic mesogenic molecules containing a chiral center which produces intermolecular forces that favour alignment between molecules at a slight angle to one another. This lead to the formation of structure which can be visualized as stack of very thin 2D nematic like layers with the director in each layer twisted w.r.t. those above and below.

The molecules shown are merely representation of many chiral nematic mesogens lying in slabs of infinitesimal thickness with distribution of orientationaround the director. This is not to be confused with planar arrangement found in smectic mesophases.

An important characteristics of cholestric mesophase is pitch. The pitch is defined as the distance it takes for the director to rotate one full turn in helix. The wavelength of reflected light can also be controlled by adjusting the chemical composition, since cholectrics can either consist of exclusively chiral molecules or of nematic molecules with chiral dopant dispersed throughout. The dopant concentration is used adjust chirality and pitch.