Poly azobenzene units, change

Investigation of light-induced conformational changes has also been extended to solid films of azobenzene-containing poly(L-aspartate)s, but no conformational change was induced by photoisomerization of the azobenzene units. This was probably due to the limited mobility of the polypeptide chains in the films. 57 ... 

Fig. 16 Poly(L-glutamic acid) containing 85 mol % azobenzene units (III). Change in solubility in HFP/water= 85/15 as a function ofthe trans-cis isomeric composition of the azo side chains.

K. Aoki, T. Seki, M. Sakuragi, and K. Ichimura, Reversible alignment change of liquid crystals induced by photochromic molecular films, Part 15. Convenient methods to prepare command surfaces by surface-selective modifications of poly(vinyl alcohol) thin films with azobenzene units, Makromol. Chem. 193, 2163-2174 (1992). 

In the study of CDs containing PEG, i.e. poly(ethylene glycol) chain, terminated by azobenzene unit, the thermal and photochemical conformational changes of trans-52 were analyzed in aqueous solution [101]. The results of the thermal study show that at low concentration trans-52 exists at 80°C as a dethreading form 53. At GO C trans-52 exists as a self-inclusion complex 54 where the CD cavity entraps the azobenzene moiety and at 1°C the self-inclusion complex 55 where CD cavity encircles the carboxylic acid unit is present. It was observed that at high concentration trans-52 forms intermolecular complexes 56. 

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