Photoorientation of azobenzene side groups in a liquid-crystalline polybutadiene-based polymer

The light-induced orientation of azobenzene side groups of a polybutadiene based liquid crystalline polymer was studied. The polymer is based on HO-terminated telechelic polybutadiene Krasol LBH 3000 grafted with 5-(4-{[4-(octyloxy)phenyl]azo}phenoxy)pentane-1-thiol units. Linearly polarized light of wavelengths 325, 365 and 488 nm influenced the photoorientation process. While irradiation with the 325 and 488 nm light generated optical anisotropy, UV light of 365 nm resulted in isotropic films. Pre-irradiation with the 365 nm light and subsequent irradiation with 325 nm led to dichroic ratio of about RD = 11. Further irradiation with 365 nm erased the anisotropy again.