Azobenzenes/-mesogens, chiral nematics

A large number of azobenzene-based amorphous and liquid crystalline polymers, particularly polyacrylates and polymethacrylates with chiral azobenzene pendants, have been prepared for the development of data storage and photonic devices [1-3,11-14]. For instance, the introduction of optically active mesogenic azobenzene residues into the side groups of the polymers produces chiral nematic and cholesteric phases, which are regulated by photoisomerization of the azobenzene units [10,14]. In most cases, however, the optical activity and chiroptical... 

Photoresponsive molecules are important for the fabrication and photomodulation of photoresponsive CLC materials, no matter if they are employed as chiral mesogens, achiral nematic LC hosts, or chiral/achiral guest molecules. The most important property of these molecules in photoresponsive CLC materials is the changes in molecular shape (geometry/conformation) as a result of the light-induced isomerization, which constitutes the basis for photomning of the properties of CLCs [18], The first example of using photoresponsive molecules to modulate the properties of CLCs was reported by Sackmann in 1971 [19], where azobenzene was employed as the dopant molecule. To date, various kinds of photoisomerizable molecules have been developed for this purpose (Fig. 5.3). 

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