Theoretical models for photoinduced birefringence and chiral structure formation in achiral azobenzene-containing materials were proposed considering phototriggered molecular reorientation via <i>trans-cis-trans</i> photoisomerization cycles of azobenzene. The photoisomerization cycles were expressed by two rate equations of the orientation distributions of <i>trans-</i> and <i>cis-</i>forms. Phototriggered molecular reorientation by illuminating linearly polarized light was verified theoretically. The photoinduced helical structure formation was simualted by elliptically polarized light. The molecular rotation angle was dependent on the sign of the ellipticity. The time evolution of the helical structure formation was consistent with the experimental result that reported by other papers.
A novel photoresponsive polymer containing bisazo chromophores have been synthesized for comparative study with
monoazo polymer. Since the bisazo structure has an extended Π-conjugation electronic system, it is expected to have
large intrinsic molecular birefringence that can realize large macroscopic photoinduced birefringence (Δn<sub>PI</sub>) via
photoinduced molecular re-orientation process of bisazo molecules. As a result, it was found that the large value of Δn<sub>PI</sub>
(0.17) could be obtained by using bisazo polymer at 514.5nm excitation with 1.0W/cm<sup>2</sup>.
In this paper, new azobenzene copolymers (PCDY and PPDY) with large photoinduced birefringence and good long-term stability of a recorded data have been introduced. The largest photoinduced value of 0.289 was obtained on the PCDY50 at 458 nm light irradiation. This value was brought about a result of molecular cooperative reorientation of cyanoazo and bisazobenzene moieties. It should be noted that the PCDY50 exhibited quite stable characteristics on the archival viewpoint. Furthermore, if we can optimize experimental conditions, more than 10<sup>5</sup> cycles of reversible data storage could be achieved. Making use of these superior characteristics of the PCDY50, an application for rewritable holographic memory and/or other optical addressable devices is anticipated.