Photoinduced anisotropy in a series of azobenzene copolymers

In order to optimize the parameters of the photoinduced birefringence in azopolymers, we have synthesized and studied copolymers with different weight ratios of two monomers which differ in the length of spacer between the azochromophore and the polymer backbone. The polymer PI based only on the first monomer is amorphous, and the polymer P-2 which contains only the second monomer is liquid-crystalline (LC). In addition to the homopolymers P-1 and P-2, five copolymers were synthesized, described by the general formula P-1(100 - x)P-2(x), where x gives the percent weight ratio of the second monomer in the final copolymer. As a result the following seven polymers were obtained - P-1, P-1(75)P-2(25), P-1(60)P-2(40), P-1(50)P-2(50), P-1(40)P-2(60), P-1(25)P-2(75), P-2. The main parameters of the photoinduced birefringence in these polymers, such as maximal value, response time and time stability, have been measured and compared.