PHOTOINDUCED ALIGNMENT OF POLYMER LIQUID-CRYSTALS CONTAINING AZOBENZENE MOIETIES IN THE SIDE-CHAIN - 1 - EFFECT OF LIGHT-INTENSITY ON ALIGNMENT BEHAVIOR

Polydomain films of liquid crystalline polymer (MACB-AB6) with low con tent (6 mol %) of azobenzene units were prepared and irradiated with l inearly polarized light at 366 nm, thus inducing an alignment of the p hotochromic side groups as well as the nonphotoactive mesogens, the cy anobiphenyl groups. An induced order parameter, S, was obtained from p olarized UV and IR spectroscopy, and it increased with increase in tem perature at first and then decreased due to phase transition. The effe ct of light intensity on the alignment behavior has been investigated in detail. Alignment change can take place even for a low intensity (0 .7 mW/cm(2)) of irradiation light. Irradiation light at high intensity induced alignment as well as a phase transition at relatively low tem perature. A higher saturation order parameter and faster achievement o f the order parameter were obtained, since a higher concentration of c is-azobenzene was produced when the film was exposed to polarized ligh t with a higher intensity. This is due to the angular-dependent absorb ance of irradiation light by the azobenzene moieties.