Abstract
Monomolecular films of a poly(vinyl alcohol) derivative having an azobenzene (Az) side chain (6Az10-PVA) transferred onto mica by the Langmuir−Blodgett technique were observed by atomic force microscopy in the noncontact mode. Multifarious features of the film morphology after the thermal and photostimulated processes were revealed, which were strongly dependent on the humidity of the atmosphere, the lateral packing density of the monolayer, and the light exposure dose. In a humidified atmosphere, a low-density film (1.2 nm2 Az-1) showed a network morphologythat exhibited a two-dimensional expansion upon irradiation with UV (365 nm) light (trans → cis Az isomerization). The films having the higher densities (0.4 or 0.3 nm2 Az-1) gave spongy-shaped or partially collapsed films and indicated a formation of three-dimensional protrusions on UV light illumination. In comparison with the spectroscopic data, these morphological changes could be related with the proceeding of the Az photoreaction. The morphologic...
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