Reorientation of azobenzenes

As mentioned in Section 5.1, the reorientation of azobenzene photo-chromic moieties under illumination with polarized light and the birefringence that is induced from it are well known and covered in many publications. 

Fischer, X., Menzel, H., and Stumpe, J, Photo-reorientation of azobenzene side groups of thermotropic hairy rod polyglutamate in LB multilayers. Supramol. Sci. 4, 543 (1997). 

Hill, R. A., Dreher, S., Knoesen, A., and Yankelevich, D. R. Reversible optical storattf utilizing pulsed, photoinduced, electric-field-assisted reorientation of azobenzenes. Apfihetl Physics Letters, vol. 66, (no. 17), 24 April 1995, p. 2156-2158. 

The photoselection in azobenzene polymers (Figure 11) is rather a general phenomenon.77-84 Systematic studies have been conducted by Natansohn and coworkers on the photoinduced molecular reorientation of azobenzene units to induce birefringence and dichroism of thin films of acrylate amorphous polymers with Dispose Red (DR) pendant residues, which have been attracting extensive... 

Fig. 2 Schematic representation of the reorientation of azobenzene chromophores by excitation with linearly polarized light. Since both the cis and the trans state are excited by illumination with the writing wavelength, the molecules perform repeated reorientations until they end up with their transition dipole moments perpendicular to the light polarization. (Adapted with permission from [8]. Copyright Wiley-VCH Verlag GmbH Co. KGaA)...

Han M, Morino S, Ichimura K. 1999. Successive occurrence of biaxial reorientation of azobenzene chromophores of a liquid crystalline polymer induced by linearly polarized light. Chem Lett 28 645 646. 

Saishoji A, Sato D, Shishido A, Ikeda T. 2007. Formation of Bragg gratings with large angular multiplicity by means of photoinduced reorientation of azobenzene copol5mers. Langmuir 23 320 326. 

Saishoji, A., Sato, D., Shishido, A. Ikeda, T. (2007). Formation of Bragg Gratings with Large Angular Multiplicity by Means of the Photoinduced Reorientation of Azobenzene Copolymers. Langmuir, 2007,23,320-326. 

Figure 16 Photoinduced reorientation of azobenzene molecules with linearly polarized light (a) Random orientation before photoirradiation (b) photoselection (c) uniaxially aligned state.

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