Photoinduced Birefringence and Surface Relief Gratings in Novel Polyurethanes with Azobenzene Groups in the Main Chain

Three novel polyurethanes with V-shaped bisazo groups (PU1 and PU2) or rodlike monoazo groups (PU3) in the main chain were synthesized. On irradiation with a linearly polarized laser beam, birefringence was induced in the three films to the level of 0.035, 0.037, and 0.044 for PU1, PU2, and PU3, respectively. The stable birefringence obtained at T g − T = 33 °C was 71%, 46%, and 19% of that achieved at room temperature for PU1, PU2, and PU3, …