AZO POLYMERS FOR REVERSIBLE OPTICAL STORAGE .6. POLY[4-[2-(METHACRYLOYLOXY)ETHYL]AZOBENZENE]

Poly[4-[2-(methacryloyloxy)ethyl]azobenzene] (pMEA) has been synthesized and its reversible optical storage properties tested in comparison with previously,reported electron-donor-electron-acceptor substituted azobenzene-containing polymers. The cis-trans thermal isomerization rate is fairly slow in pMEA, and while it is possible to induce birefringence using UV-polarized light, the levels and rates are not reproducible, due to the persistent cis population. Birefringence can, however, be induced with polarized visible light (514.5 nm), but at lower levels than in the previous polymers, due to the lower absorbance levels at this wavelength. The efficiency of the inducing birefringence process is about 4.3 x 10(-6) cm(3)/J and is comparable to the efficiency of the same processes in the previous polymers only if the differences in absorbances are considered. pMEA is also a good substrate for high efficiency diffraction gratings inscription on the film surface. A 90-nm grating (4% efficiency) can be obtained in only 35 min of irradiation with 22 mW/cm(2) at 514.4 nm.