Mumbai university > FE > SEM 1 > Applied Physics 1

Marks: 5M

Year: Dec 2013

Mesomorphic state of matter:-

• Mesomorphic state of matter is a state of matter intermediate between liquid and solid.

• It occurs with the solids having greater tendency to an ordered arrangement.

• It has certain properties of solids like double refraction of light or interference pattern in polarised light.

• It also has some properties of liquid, like surface tension, flow and viscosity.

Cholesteric Phase:-

• Composed of molecules containing a chiral center which produces intermolecular forces that favour alignment between molecules at a slight angle to one another.

• The structure can be visualized as a stack of very thin 2-D nematic-like layers with the director in each layer twisted with respect to those above and below forming a continuous helical pattern about the layer normal.

• They organize in layers with no positional ordering within layers, but a director axis which varies with layers.

• The variation of the director axis tends to be periodic in nature.

• The period of this variation (the distance over which a full rotation of 360° is completed) is known as the pitch, p. This pitch determines the wavelength of light which is reflected.