Spectrophotometric investigation of photoinduced processes in methacrylic azobenzene-containing polymers

The photoinduced processes in four methacrylic azobenzene-containing copolymers have been investigated. The materials have been synthesized by radical type polymerization of the chromophore monomer and methylmethacrylate. The copolymers differ only in the concentration of chromophore monomers (P1 - 5mol%, P2 - 23mol%, P3 - 5Omol% and P4 - 100mol%). The first three polymers are amorphous and the fourth (P4) is liquid-crystalline. We have established that the photoequilibrium concentration of cis-azobenzenes obtained on irradiation with nonpolarized UV light and with a linearly polarized Ar beam decreases with increasing concentration of chromophore monomers: it is highest for polymer P1 and lowest for P4. Similarly, values for the observed dichroism induced by polarized light can be linked to chromophore concentration. But here lower values of the concentration of chromophores correspond to lower values for photodichroism. This, however, does not hold for the P4 polymer and this is most probably caused by its liquid-crystalline properties.