Unconventional polarization characteristic of rapid photoinduced material motion in liquid crystalline azobenzene polymer films

Abstract

We carried out double-beam interference experiments using an argon ion laser with controlled polarization in order to cause the formation of photoinduced surface relief in liquid crystalline azobenzene polymer films. The irradiation was undertaken on a film in the cis-rich state obtained by a pre-exposure to ultraviolet light. In this procedure, the efficiency of the photoinduced mass transfer was high, more than 1000 times greater than hitherto reported for amorphous azobenzene polymers. This approach revealed the unusual nature of the migration process. Rapid mass migration is promoted by intensity holographic recording, independent of the polarization of the light used for the irradiation. This insensitivity with respect to the polarization of the light led us to the conclusion that rapid mass migration starting from a cis-rich azobenzene polymer is predominately driven by phototriggered elemental processes such as local dewetting, self-organizing motion, and translation diffusion.