Liquid crystals in electric and magnetic fields—a delicate response

Liquid crystals in electric and magnetic fields—a delicate response 

The electric polarisation in liquid ciystals was discussed in Chapter 2 as an example of an anisotropic property. In short, the application of an electric field E to a liquid crystal produces a dipole moment per unit volume, called the polarisation and given the symbol 

The polarisation depends linearly on the electric field, but the anisotropy of the liquid 

so the polarisation has units of C/m in accordance with its definition as the dipole moment (Cm) per xmit volume (m ). 

The electric field and polarisation together define the electric displacement, D, 

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Liquid Crystals in Electric and Magnetic Fields—A Delicate Response 201... 

The response of liquid crystals to electric and magnetic fields is one of their most interesting properties. The presence of orientational order produces a response only possible when the molecules in a macroscopic volume of a substance behave cooperatively. Since the fluid nature of the liquid crystal phase offers little resistance to this cooperative behaviour, only weak electric and magnetic fields are necessary to produce these significant responses. This is what makes liquid crystals nature s delicate phase of matter. 

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