Factors affecting in-plane and out-of-plane photoorientation of azobenzeneside chains attached to liquid crystalline polymers induced by irradiationwith linearly polarized light

Photoinduced orientational behavior of polymethacrylates with side chains ( amorphous polymers, pMAz2 and C2nMeO, and liquid crystalline polymers, C6Me O and C12MeO) with different; alkylene spacer lengths (n = 2, 6, 12) were i nvestigated by means of polarized Fourier transform infrared (FT-IR) and UV -vis absorption spectroscopy. Being different from pMAz2, C2MeO showed high optical anisotropy due to in-plane orientation and the excellent thermosta bility even above T-g, which can be explained in terms of potential liquid crystallinity to be able to have a tendency to form a well-ordered domain. We observed marked dependence of photoorientation processes on film tempera tures of C6MeO. While in-plane orientation was generated in glassy state as well as at 76 degrees, irradiation at 90 degrees C slightly lower than T-S N (transition temperature between smectic and nematic phases) gave rise to the distinct transformation from in-plane orientation at the early stage to successive out-of-plane reorientation, which was accompanied by H-aggregat ion. This situation enabled ones to record optical images in a C6MeO film o n the basis-of the difference in birefringences between two orientational m odes. The biaxial reorientation occurred also for C12MeO, though both in-pl ane and out-of-plane photoorientation occurred simultaneously at room tempe rature as well as elevated film temperatures.