Effects of chemical structure of diisocyanate in polyurethanes on the diffraction efficiency

Abstract In this study, we report the syntheses and diffraction efficiency of four different disperse red-polyurethanes (DR-PU n ’s) containing azobenzene group in the side chain. The effects of chemical structures of diisocyanates in four different DR-PU n ’s were studied on the diffraction efficiency induced by the laser beam. The DR-PU n ’s with toluene-2,4-diisocyanate or toluene-2,6-diisocyanate exhibited diffraction efficiencies, but the DR-PU n ’s with diphenyl structure of diisocyanate in the main chain did not show diffraction efficiencies. It was found that for the DR-PU2 having the molecular weight larger than 16,000 shows good optical storage behavior and that the maximum diffraction efficiency reached to 0.35%.