15 February 2017 Photoresponsive smart surface of LC azo-dendrimer: photomanipulation of topological structures and real-time imaging at a nano-scale
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Abstract
In this paper, we review some results on our recent studies on photo-induced phenomena of liquid crystals (LCs) by means of interfaces decorated with a photo-responsive azobenzene dendrimer (azo-dendrimer). The azo-dendrimer molecules doped in a LC are spontaneously segregated from bulk and adsorbed onto substrate/LC or solvent/LC interfaces, and their photo-isomerization can bring about the so-called anchoring transition, i.e. reversible switching between homeotropic and planar alignment states of the bulk LC, when exposed to UV/VIS light. In addition to photoinduced anchoring transition in a LC cell, several interesting photo-induced phenomena through the azo-dendrimerdecorated interfaces have been reported, such as photo-induced transformation of the interior topological structures of nematic, cholesteric and smectic droplets, photo-mechanical motion of the micro particles dispersed in a nematic matrix, and optical assistance of the athermal anchoring transition with the aid of a perfluoropolymer surface. In addition to such phenomena, we also discuss the conditions of such photo-responsive interfaces in terms of the polar anchoring energy at the interface upon photo-isomerization under illumination of UV and/or VIS lights. The anisotropy of the polar anchoring energy was evaluated experimentally by means of Polarization Microscopy (POM), Dielectric Spectroscopy (DS), Second Harmonic Generation (SHG), and Attenuated Total Reflection Fourier Transform Infrared (ATR-IR) Spectroscopy, and theoretically based on the simple Rapini-Papoular model. We also demonstrate the continuous bulk orientation change by the photo-dynamic process through the fine control of the polar anchoring energy. Besides, the state-of-the-art video-rate atomic force microscopy (ν-AFM) was carried out to visualize the dynamics of such interfaces at a nano-meter scale.
Conference Presentation
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Fumito Araoka, Alexey Eremin, Satoshi Aya, Guksik Lee, Atsuki Ito, Hajnalka Nadasi, Nerea Sebastian, Ken Ishikawa, Osamu Haba, Ralf Stannarius, Koichiro Yonetake, Hideo Takezoe, "Photoresponsive smart surface of LC azo-dendrimer: photomanipulation of topological structures and real-time imaging at a nano-scale", Proc. SPIE 10125, Emerging Liquid Crystal Technologies XII, 101250H (15 February 2017); doi: 10.1117/12.2251128; https://doi.org/10.1117/12.2251128
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