Photoinduced alignment of polymer liquid crystals containing azobenzene moieties in the side group VII. On He-Ne laser beam irradiation

Photoinduced alignment in a polymer liquid crystal prepared from 6-{1-[4-(2 -cyano-4-nitrophenylazo)phenyl]piperazino}hexyl acrylate and 4'-[6-(methacr yloyloxy)hexyloxy]-4-cyanobiphenyl was investigated for the first time on i rradiation with a polarized He-Ne laser beam at 633 nm. The azobenzene moie ties as well as the inert cyanobiphenyl mesogenic units were aligned with t he molecular long axis perpendicular to the polarization direction of the i rradiation light. Alignment induced on short irradiation was reversible, wh ile that induced under prolonged irradiation was irreversible due to the oc currence of crosslinking which might be caused by photoinduced decompositio n of the azobenzene moieties during the photoirradiation process.