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ChemistryOpen. 2017 December; 6(6): 684.
Published online 2017 November 8. doi:  10.1002/open.201700170
PMCID: PMC5715237

Reversible Broad‐Spectrum Control of Selective Reflections of Chiral Nematic Phases by Closed‐/Open‐Type Axially Chiral Azo Dopants

Abstract

Invited for this month's cover picture is the groups of Professor Hirotsugu Kikuchi and Dr. Yasushi Okumura at the Institute for Materials Chemistry and Engineering at Kyushu University (Japan). External dynamic control of molecular self‐organized superstructures with unique features has been researched, as these structures are applicable to chiral molecular devices. The cover picture shows photocontrol of selective reflection color that originated from the self‐organized helical structure of chiral nematic liquid crystals (N*LCs) using closed‐/open‐type dopants. The drastic structure changes of the dopants by light stimuli enable reversible broad‐spectrum control of selective reflections of N*LCs with opposite helical sign. Read the full text of the Full Paper at 10.1002/open.201700121.

How would you describe to the layperson the most significant result of this study?

If we can reversibly controlled optical chirality of N*LCs by light stimuli, spectrum control of reflections of N*LCs is enabled. In this work, we attempt photocontrol of helical structure of N*LCs, induced by using newly synthesized closed‐ and open‐type chiral dopants. Consequently, in the N*LCs with closed‐type chiral dopants, the RGB color reflection is quickly modulated by light. By contrast, open‐type photo‐tune multicolor reflections and invert the handedness of circular polarizing light (CPL) in a wide range of NIR/SWIR. Thus, we successfully achieve broad‐spectral photocontrol of selective reflections over entire range of UV, Vis, and NIR (SWIR) light. Such a material will have a great impact on color information technologies!

Scheme 1
The groups of Professor Hirotsugu Kikuchi and Yasushi Okumura

What do you consider the exciting developments in the field?

Among of external stimuli such as light, electric field, and temperature, light is particularly attractive because it allows remote, spatial, and temporal photocontrol of the chirality of N*LCs without detrimental effect to the reflection intensity or width of reflection bands, unlike in electrocontrol of color reflection. Thus, the exciting development in this field is ultimate manufacturing of unique photo‐driven devices such as tunable LC laser, tunable LC color filters and optically addressed flexible display without patterned electronics through a nanofabrication approach based on modulation of the optical chirality of N*LCs by light.

What was the inspiration for this cover design?

Hiroya Nishikawa and his friend, Guilherme Leao de Oliveira, illustrated this cover design. Our group has successfully achieved photocontrol multicolor of selective reflections of N*LC with opposite helical sign induced by closed‐/open‐type dopants through light exposure. Thus, we express two opposite helical structures (middle coils), photoswitchable multicolor (upper cylinders), “key” dopants (bottom objects) and light stimuli (bottom shine). Moreover, as a background picture, we adopt ′beautiful sunset′ because we believe the sunset is one of a straightforward view to represent natural multicolour.

Acknowledgements

This work was partially supported by a Grant‐in‐Aid for Scientific Research (A) JSPS KAKENHI (grant number JP25248021) from the Japan Society for the Promotion of Science and Dynamic Alliance for Open Innovation Bridging Human, Environment and Materials from the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan, and CREST, JST (JPMJCR1424). An external file that holds a picture, illustration, etc.
Object name is OPEN-6-684-g003.jpg

Notes

H. Nishikawa, D. Mochizuki, H. Higuchi, Y. Okumura, H. Kikuchi, ChemistryOpen 2017, 6, 684.

Contributor Information

Hiroya Nishikawa, pj.ca.u-uhsuyk.mc@awakihsin.

Prof. Hirotsugu Kikuchi, pj.ca.u-uhsuyk.mc@ihcukik.


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