PHOTOINDUCED SURFACE-RELIEF GRATINGS IN HIGH-T-G MAIN-CHAIN AZOAROMATIC POLYMER-FILMS

We have synthesized two classes of polyureas with mono-and bisazoaroma tic groups in their main chains via reactions between isophorone diiso cyanate and the corresponding diamines. Holographic gratings were fabr icated on azoaromatic polyurea films prepared by spin-coating from sol utions. The effect of high glass transition temperature and dipole mom ent of azo groups on the formation of gratings was investigated. Altho ugh the two polymers have relatively high glass transition temperature s (197 and 236 degrees C), chromophore alignment was induced by laser beam irradiation at modest Light intensities. Regularly spaced surface relief gratings on the polymer film were also recorded upon exposure to an interference pattern of two polarized argon laser beams. Erasure could be achieved by heating above T-g, or by exposure to one of the beams in a manner similar to low-T-g, side-chain azo polymers. (C) 199 8 John Wiley & Sons, Inc.