Photoinduced behaviors of isocyanate-based azo molecular glass and polymer

Azobenzene functionalized polyisocyanate and cyclic trimer with the same chemical composition were synthesized via anionic living polymerization. Thin films were prepared through a simple spin coating process, especially even with low molecular weight of trimer, it was possible to form optically transparent films. Photoinduced phenomena of dichroism, birefringence and holographic surface relief grating formation were investigated in relation to their molecular structures by irradiation of Ar ion laser beam. Compared to the azo polymer, generally the cyclic trimer showed faster growth rate of birefringence and increased diffraction efficiency during holographic surface grating formation, due to the absence of long polymer backbones and the lack of their complicated entanglements, but the final saturated values were smaller. The efficient surface relief grating formation was confirmed from the AFM images, which showed regularly defined sinusoidal relief structures.