Photoinduced Alignment and Structuring in Thin Films of Azobenzene-Containing Liquid Crystalline Polymers

When an azobenzene (Az) unit is embedded in molecular assemblies such as liquid crystalline (LC) systems, the state and orientation of the surrounding LC matrix are strongly coupled with the photoisomerization reaction of Az. Due to the strong cooperative nature of LC materials, the light-driven molecular motion of Az gives rise to largely amplified photoresponses. This chapter briefly summarizes our recent activities on the photoresponsive LC thin films containing the Az unit. The motions of a wide range of size feature from nanometer levels to macroscopic levels can be driven using the side-chain Az LC polymers of almost the same structural features. The processes include light-switchable surface alignment of LC materials (nanoscopic scales at interfaces), photoalignment in a surface-grafted polymer film, photocontrol of microphase separation patterns at mesoscopic scales (10–100 nm), and mass migrations at micrometer scales. The versatility and wide applicability of the thin films of Az LC polymers are demonstrated.