title: Control of the orientation and photoinduced phase transitions of macrocyclic azobenzene.
abstract: Photoinduced phase transitions caused by photochromic reactions bring about a change in the state of matter at constant temperature. Herein, we report the photoinduced phase transitions of crystals of a photoresponsive macrocyclic compound bearing two azobenzene groups (1) at room temperature on irradiation with UV (365 nm) and visible (436 nm) light. The trans/trans isomer undergoes photoinduced phase transitions (crystal-isotropic phase-crystal) on UV light irradiation. The photochemically generated crystal exhibited reversible phase transitions between the crystal and the mesophase on UV and visible light irradiation. The molecular order of the randomly oriented crystals could be increased by irradiating with linearly polarized visible light, and the value of the order parameter was determined to be -0.84. Heating enhances the thermal cis-to-trans isomerization and subsequent cooling returned crystals of the trans/trans isomer.
authors: Electronics and Photonics Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Central 5, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8565 (Japan).
authors: Emi
authors: E
authors: Uchida
authors: Kouji
authors: K
authors: Sakaki
authors: Yumiko
authors: Y
authors: Nakamura
authors: Reiko
authors: R
authors: Azumi
authors: Yuki
authors: Y
authors: Hirai
authors: Haruhisa
authors: H
authors: Akiyama
authors: Masaru
authors: M
authors: Yoshida
authors: Yasuo
authors: Y
authors: Norikane
keywords: crystal growth; isomerization; phase transitions; photochemistry; photochromism; self-assembly