We present trial calculations of surface light-induced patterns in photochromic azo-substituted polymers. Using microscope with nanopositioning stage various birefringence and surface structures have been recorded in photochromic azo-functionalized polymers. By systematic approach to the inscription experiment and controlling cw or pulsed laser light intensity, its polarization and beam scan speed we observed the dynamics of molecular photoorientation and its relation to mass transport. We discuss properties of holographically inscribed polarization gratings and analyze them spatially by monitoring of microscopic local diffraction efficiency. We report how azo-benzene molecules can work in other systems, i.e. azobenzene functionalized POSS molecules embedded in nematic liquid crystal.
A series of new polyesterimides (PEIs) containing photochromic azobenzene moieties have been synthesized. For this purpose the following diesterdianhydrides with azobenzene groups have been prepared: 2,2'-{4-[(4-nitrophenyl)-azo} phenyl]iminobis(ethyl benzene-1,2-dicarboxylic acid anhydride-4-carboxylate), 2,2'-{4-[(4-methylphenyl)-azo}phenyl] iminobis(ethyl benzene-1,2-dicarboxylic acid anhydride-4-carboxylate) and 2,2'-{4-[(4- fluorophenyl)-azo}phenyl] iminobis(ethyl benzene-1,2-dicarboxylic acid anhydride-4-carboxylate). The polyesterimides have been obtained from diesterdianhydrides and 1,3-phenylenediamine using high-temperature polycondensation. The resulting polyimides are characterized as having good solubility in some solvents, high glass transition temperatures (168-210°C) and good film forming properties. The irradiation with linearly polarized light causes a reorientation of the azobenzene groups by angular-selective E/Z photoisomerization. In this way optical anisotropy is induced in the initially isotropic films casting from solution of the amorphous polymers. The photoinduced dichroism in the films has been measured to investigate the effect of azobenzene substitution.
Light-induced optical anisotropy have been studied by laser grating inscription method within the group of novel azobenzene functionalized polymers. Undergoing light-induced trans-cis-trans photoisomerisations azo-benzene groups were covalently bonded to the main chains of polymers. Two-wave mixing technique was employed to inscribe the amplitude and phase gratings in these polymers. Using two light polarization geometries s-s an s-p we were able to study differences in grating properties as well as ability of surface relief grating formation in studied class of polymers. The supplementary technique of moving grating was used as a tool for obtaining information on contribution of various reorientations of chromophores and main chains to light diffraction on the obtained periodic structures.
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