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The synthesis and optical properties of a series of amorphous polyesters with amino-sulfone azobenzene chromophores in the main chain are presented. The condensation of alkyl diacid chlorides with 4-[(2-hydroxyethyl)ethylamino]-4′-(2-hydroxyethylsulfonyl)azobenzene (7) gave polymers that showed low and unstable photoinduced birefringence because of their low glass-transition temperature. The condensation of 7 with mixtures of adipoyl chloride and terephthaloyl chloride gave a polymer with a higher glass-transition temperature and a stable reversible photoinduced birefringence. A photostationary birefringence of 0.07 was observed. Surface profile gratings were optically inscribed and produced diffraction efficiencies less than or equal to 19%. Photostationary, long-term stable birefringence and surface-grating efficiency increased with polymer rigidity. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2245–2253, 2000

Spontaneous hexagonal pattern formation in the transverse profile of a continuous laser beam reflected back by a planar mirror onto a nematic liquid crystal cell is experimentally investigated. The effect is proved to occur at pump intensities as low as 10W/cm2.