Influence of the substituent on azobenzene side-chain polyester optical storage materials

A number of poly(1,3-propylenetetradecanedioates) or poly(1,3-propyleneadipates) with pendant p-substitued azobenzenes linked through a hexylene spacer in the 2-position are prepared. The substituents comprise: cyano, nitro, methoxy, hydrogen, methyl, n-butyl, phenyl, fluoro, trifluoromethyl, chloro, and bromo. C-13 NMR spectroscopic and molecular mass investigations substantiate good film forming characteristics. The optical storage performance of thin polyester films are investigated through polarization holography. The resulting diffraction efficiency is mapped and discussed as a function of irradiation power and exposure time. Polytetradecanedioates with cyano-, nitro-, methyl-, fluoro-, or trinuoromethyl-azobenzene reach more than 50% diffraction efficiency. Investigations of anisotropy induced at different temperatures reveal that the polyesters are only photosensitive in a narrow temperature range around T-g.