Photoisomerization of disperse red one in films of poly(methyl-methacrylate) at high pressure

Evanescent wave optics under high pressure is developed for the optical and mechanical characterization of thin films. Both the attenuated total reflection in the Kretschmann configuration and the grating coupling techniques are implemented. We apply total internal reflection and surface optical wave, e.g. surface plasmon spectroscopy, in order to gain information about the pressure dependence of the optical and mechanical properties of the pressure medium and the metal coupling layer. Optical modes guided in thin films allow us to characterize the pressure effects on these films. We show that hydrostatic pressure applied to thin polymer films increases their refractive index and decreases their thickness. The pressure increases the density of these films by a reduction of the free volume. As far as microscopic environments are concerned, we show that the molecular movement induced by photo- and thermal isomerization of an azo chromophore flexibly tethered to a poly(methyl-methacrylate) polymer is hindered by increasing the pressure. (C) 2000 Elsevier Science B.V. All rights reserved.