Azobenzene-based polymers formation

Izumi and coworkers carried out similar preparations of conjugated polymers with azobenzenes in the main chain [212, 213]. Application of various palladium-catalyzed coupling methods such as the Suzuki coupling and the Heck reactions allowed formation of poly(p-phenylene)- and poly(phenyl vinylene)-based polymers ... 

The first example of halogen-bonded liquid crystal with additional functional properties appeared in 2012 when an azobenzene-based system capable of combining a high degree of photoinduced anisotropy and exceptionally efficient SRG formation was reported [12]. The structure of the complex is shown in Fig. 7. The design is rather unusual because of the lack of flexible alkyl chains, which have been reported to suppress the formation of SRGs in LC polymers [56]. 

Fukuda, X., Sumaru, K., Yamanaka, X, and Matsuda, H. Photo-induced formation of the surface relief grating on azobenzene polymers Analysis based on the fluid mechanics. Mol. Cryst. and Liq. Cryst. 2000, 345, pp. 263-268. 

In addition to the above-mentioned polymer-based blends, azobenzene-containing sol-gel-based systems are a third material class. It was shown by Stumpe et al. that an efficient SRG formation can be obtained using ionic azobenzene units, which were stabilized in a polyelectrolyte matrix via an in situ sol-gel reaction [59],... 

Note that the sol-gel materials based on polysiloxane have been known for their durability and good optical quality. If functionalized with azobenzene moieties, they exhibit nonlinear optical properties and photoinduced anisotropy. There are a few examples of SRG inscribed onto materials (Kim et al., 2006b Chaput et al., 2000 Frey et al., 2000 Darracq et al., 1998). The gratings could be inscribed only in freshly prepared films, whereas in aged films, the cross-linking of the polymer completely hindered SRG formation. 

Dimitrov et al, 2007 Schild, 1992). Furthermore, switchable comonomers can be introduced resulting in the formation of multistimuli-responsive copolymers. Examples of such multiresponsive polymers include pH-responsive materials based on the incorporation of pH-switchable side chains, such as tertiary amines or carboxylic adds, and UV responsive materials based on the incorporation of UV-switchable side groups, such as azobenzene or spiropyran moieties (Dimitrov et al, 2007 Roy et al, 2010,2013). 

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