Azobenzene polymers isomerization pressure

This chapter is organized as follows. Section 4.2 addresses the study of photoisomerization and photoinduced orientation of azobenzene molecules at the molecular level in SAMs of azo-silane molecules. Section 4.3 discusses photoinduced effects in supramolecular assemblies, i.e., LBK multilayer structures containing azobenzene molecules, and compares the photoinduced movement of azobenzenes in these structures to that observed in spin-cast films. Section 4.4 focuses on the isomerization and sub-Tg photoinduced orientation in a series of very high Tg (up to 350°C) nonlinear optical polyimide and thermoplastic donor-embedded polyurethane polymers containing azo dye, especially focusing on polymer structure-Tg-photoinduced molecular movement relationships. Section 4.5 describes pressure effects on photoisomerization and photo-orientation in films of a PMMA polymer containing azo dye. Finally, we make some concluding remarks in Section 4.6. 

Blair et al. [9] have carried out film balance measurements on monolayers of photochromic polymers (4) and (5). Figure 7 shows an example of the pressure-area curve for Structure (4). A significant reduction in area per monomer unit was observed on changing from dark to light conditions this was interpreted as being the result of trans-io-cis isomerization of azobenzene chromophores the more extended conformation of the fr 5-isomer would produce a large apparent area. The difference between the pressure-area curves of the meta- and /jaro-polyamide was interpreted based on the assumption that the mcto-azo-polymer chain may have a helical structure, whereas the /jara-azo-polymer has a linear structure. 

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