Abstract
This chapter reviews photoisomerization and photo-orientation in films of polymer by focusing on the influence of the chromophores environment on induced molecular movement. The chapter also compares photoisomerization of azobenzene derivatives in supramolecular assemblies such as Langmuir–Blodgett–Kuhn (LBK) multilayers, molecularly thin self-assembled monolayers (SAMs), and amorphousspin-cast films. In azo-silane SAMs, photoisomerization and photo-orientation often occurs in molecularly thin layers as much as they occur in bulk spin-cast films. In LBK multilayers of azo-polyglutamates, the polymers side-chain structure generally influences the stability of the layers stacking, and the azobenzene molecule is orientationally trapped and thus it isomerizes between a highly oriented and a bend configuration, thereby controlling the film's optical order. Highly organized LBK structures obstruct the orientational freedom required for the chromophores photo-reorientation. In amorphous spin-cast azo-polymer films, molecules are initially randomly distributed without intermolecular interaction, and photoisomerization and photo-orientation depend on the polymer structure and the free volume. It is observed that isomerization is slowed by rigid embedding into rigid backbones and high-pressure application reduces the polymer's free volume and suppresses the chromophores photoisomerization.
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