STRUCTURAL AND DYNAMIC STUDIES OF THE POLAR ORIENTATION INDUCED BY CORONA POLING AND ALL-OPTICAL POLING IN CROSSLINKABLE POLYMER THIN FILMS

摘要

Structural and dynamic studies of the induced noncentrosymmetry were performed in a reticulable polymer system with azobenzene chromophores. Growth and decay kinetics of the photoinduced second order susceptibility χ~((2)) was tested through photoinduced SHG in the samples. From fitting of the experimental results to the theoretical equation, parameters representing the cis-trans thermal backreaction and orientation scattering of trans molecules with net orientation were obtained. In particular good photostability of the induced polar orientation was demonstrated, presumably due to the fraction of molecules, which remained fixed in their positions via photoinduced reticulation reaction. Erasure mechanisms following an intense monochromatic irradiation appear to be the major limitation to the use of such systems, as the decay process determines their potential application to optical storage for instance. Yet, experiments performed recently by some research groups with crosslinkable polymers turned out to be an attractive way of improving the photo-stability of the photoinduced polar order. Another method could be the self-seeding of the optically induced orientation.