Chain compounds, birefringence polymers

For a typical chiral organic compound, such as 2-butanol, the circular birefringence, nL - wR, at A = 589 nm is of the order of 10-7. Even for a very high a = 40° mm-1 at A = 589 nm ( wL - nR 2 X 10 4), linear birefringence, which may arise from residual ordering/aggregation of polymer chains, could easily overwhelm the circular birefringence. 

The measurement of photoinduced birefringence revealed very different anisotropy. Considering the numerous compounds that could readily be complexed with this type of polymer, including chiral adds, phenols, and metals, the approach of using side-chain azopyridine polymers offers the possibility to produce a large number of new photoactive liquid crystalline materials without exhaustive synthetic efforts and with new properties to exploit. And really the approach has been exploited in recent works. The materials similar to that... 

In this chapter we shall only be concerned with electro-optic and thermo-optic switching effects in thermotropic side-chain polymer liquid crystals. We will consider briefly the synthesis and structure of such compounds and show how the nematic, cholesteric and smectic phases arise. Since the optical properties of each of these phases are different, and may be altered depending on alignment within the phase, each gives rise to different electro-optic effects. If these are coupled to the use of dye additives or substituents, then it will be realized that a wide range of electro-optic devices based on dichroism or fluorescence as well as birefringence or scattering power may be fabricated. These will be considered and discussed in terms of their performance and potential applications. Finally, possible uses of polymer-low molar mass liquid crystal solutions will be considered in terms of electro-optic device applications. 

---