title: Photomanipulation of the anchoring strength using a spontaneously adsorbed layer of azo dendrimers.
abstract: We systematically studied the photoinduced anchoring transition in a nematic liquid crystal containing azo dendrimers. Because the azo dendrimers in the trans-isomer state were spontaneously adsorbed at substrate surfaces, which was confirmed by optical second-harmonic generation (SHG), a homeotropic orientation was established at the first stage. Ultraviolet (UV) light irradiation triggered a transition into a planar state which was accompanied by a suppression of the SH generation. The monotonic decrease of the effective scalar order parameter with increasing UV light intensity was determined by polarized attenuated total reflection infrared (ATR-IR) spectroscopy. The variation of anchoring strength and extrapolation length was evaluated by observing the Fréedericksz transition as a function of UV light intensity at a certain visible (VIS) light intensity. Such a photoinduced variation can be interpreted as a variation of the anchoring strength depending on the trans/cis ratio at the surfaces based on a modified Rapini-Papoular model. Thus, this system provides the opportunity for a controlled change in the anchoring strength.
authors.affiliation: Otto-von-Guericke-Universität Magdeburg, Department of Nonlinear Phenomena, 39016 Magdeburg, Germany. alexey.eremin@ovgu.de.
authors.forename: Hajnalka
authors.initials: H
authors.lastname: Nádasi
authors.affiliation: Otto-von-Guericke-Universität Magdeburg, Department of Nonlinear Phenomena, 39016 Magdeburg, Germany. alexey.eremin@ovgu.de.
authors.forename: Ralf
authors.identifier: http://orcid.org/0000-0002-6836-3663
authors.initials: R
authors.lastname: Stannarius
authors.affiliation: Otto-von-Guericke-Universität Magdeburg, Department of Nonlinear Phenomena, 39016 Magdeburg, Germany. alexey.eremin@ovgu.de.
authors.forename: Alexey
authors.identifier: http://orcid.org/0000-0001-9743-6895
authors.initials: A
authors.lastname: Eremin
authors.affiliation: Department of Organic and Polymeric Materials, Tokyo Institute of Technology, 2-12-1 O-okayama, Meguro, Tokyo 152-8552, Japan and RIKEN Center for Emergent Matter Science, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan. fumito.araoka@riken.jp.
authors.forename: Atsuki
authors.initials: A
authors.lastname: Ito
authors.affiliation: Department of Organic and Polymeric Materials, Tokyo Institute of Technology, 2-12-1 O-okayama, Meguro, Tokyo 152-8552, Japan.
authors.forename: Ken
authors.initials: K
authors.lastname: Ishikawa
authors.affiliation: Department of Organic Materials Science, Yamagata University, 4-3-16 Jonan, Yonezawa, Yamagata 992-8510, Japan.
authors.forename: Osamu
authors.initials: O
authors.lastname: Haba
authors.affiliation: Department of Organic Materials Science, Yamagata University, 4-3-16 Jonan, Yonezawa, Yamagata 992-8510, Japan.
authors.forename: Koichiro
authors.initials: K
authors.lastname: Yonetake
authors.affiliation: Toyota Physical and Chemical Research Institute, 41-1 Yokomichi, Nagakute, Aichi 480-1192, Japan.
authors.forename: Hideo
authors.initials: H
authors.lastname: Takezoe
authors.affiliation: RIKEN Center for Emergent Matter Science, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan. fumito.araoka@riken.jp.
authors.forename: Fumito
authors.initials: F
authors.lastname: Araoka