Photochromic Behavior of New Azo - Polyimides

Aromatic polyimides containing side azobenzene groups have been synthesized by low- temperature solution polycondensation of certain aromatic dianhydrides with aromatic diamines containing preformed side azobenzene groups followed by chemical imidization at 100degC in the presence of pyridine and acetic anhydride. The polymers present a good thermostability, the degradation process starting for all the products above 300degC and the glass transition temperature of these polyimides being in the range of 185-230degC. The photochromic behavior concerning the trans-cis isomerization process of azo-groups, in solution and in solid state, was evaluated.