Synthesis and Thermal Behaviour of Polyimides Containing Pendent Substituted Azobenzene Units

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 units followed by chemical imidization at 100 degrees C in the presence of pyridine and acetic anhydride. The obtained polyimides were characterized and evaluated by FT-IR, UV-Vis, DSC and TCA analyses. These polymers show a good thermal stability with starting decomposition temperature above 300 degrees C and glass transition temperature in the range of 111-230 degrees C. These polyimides show a good solubility in various solvents. The photochromic behaviour, determined by the trans-cis isomerization process of azo-groups, in solution and in solid state, was also evaluated.