Photomanipulation of the anchoring strength using a spontaneously adsorbed layer of azo dendrimers
| Autor: | Alexey Eremin, Hideo Takezoe, Ralf Stannarius, Ken Ishikawa, Fumito Araoka, Koichiro Yonetake, Hajnalka Nádasi, Atsuki Ito, Osamu Haba |
|---|---|
| Jazyk: | angličtina |
| Rok vydání: | 2017 |
| Předmět: |
Fréedericksz transition
Stereochemistry Chemistry Infrared Homeotropic alignment General Physics and Astronomy 02 engineering and technology 010402 general chemistry 021001 nanoscience & nanotechnology Photochemistry medicine.disease_cause 01 natural sciences 0104 chemical sciences Light intensity Liquid crystal Attenuated total reflection medicine Physical and Theoretical Chemistry 0210 nano-technology Spectroscopy Ultraviolet |
| Zdroj: | Physical Chemistry Chemical Physics. 19(11):7597-7606 |
| Popis: | 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. |
| Databáze: | OpenAIRE |
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