Visualization of Photoresponsive Monolayers Comprised of Photochromic Polymers.

Abstract

Photomechanical response of the polymer monolayers having an azobenzene (Az) side chain was successfully visualized by Brewster angle microscopy (BAM) and atomic force microscopy (AFM). In situ BAM observation that covers the sub-millimeter scale range revealed clear photoinduced morphological and rheological changes. By following the photoinduced morphological changes of an isolated single domain, a couple of hitherto unknown properties have been unveiled, for example, non-linearity involved in the film expansion process, intrinsic magnitude of film expansion at zero pressure, dependence on light intensity and so forth. By AFM that observes the ranges of micrometer to nanometer levels, it was found that even on a mica surface, the Az containing monolayer shows a reversible photoinduced film deformation under highly humid conditions. These visualization techniques provided a great deal of complementary unique information which covers the scale ranges between the macroscopic Langmuir trough experiments and scale spectroscopic observations at a molecular level.