Abstract
We found possible chirality enhancement and reduction in chiral domains formed by photoresponsive W-shaped molecules by irradiation with circularly polarized light (CPL). The W-shaped molecules exhibit a unique smectic phase with spontaneously segregated chiral domains, although the molecules are nonchiral. The chirality control was generated in the crystalline phase, which shows chiral segregation as in the upper smectic phase, and the result appeared to be as follows: for a certain chiral domain, right-CPL stimuli enhanced the chirality, while left-CPL stimuli reduced the chirality, and vice versa for another chiral domain. Interestingly, no domain-size change could be observed after CPL irradiation, suggesting some changes in the causes of chirality. In this way, the present system can recognize the handedness of the applied chiral stimuli. In other words, the present material can be used as a sensitive chiral-stimuli-recognizing material and should find invaluable applications, including in chiroptical switches, sensors, and memories as well as in chiral recognition.
Highlights
Since Pasteur succeeded in separating two isomers of sodium ammonium tartrate in 1848,1 chirality has been regarded as an intriguing and universal phenomenon in nature
We found possible chirality enhancement and reduction in chiral domains formed by photoresponsive W-shaped molecules by irradiation with circularly polarized light (CPL)
Smectic layers form a helical structure like the twist grain boundary (TGB) phase,[21] but the twist is continuous unlike TGB
Summary
Since Pasteur succeeded in separating two isomers of sodium ammonium tartrate in 1848,1 chirality has been regarded as an intriguing and universal phenomenon in nature. The same as previous examples, the HNF phase microscopically segregates into two chiral domains with equal probabilities. The SmX phase appears as a fine filament growth, and chiral domains are spontaneously formed in the SmX and the crystalline phases like in the B4 phase.[32] Based on detailed experiments such as optical observations and X-ray diffraction (XRD) studies, a model structure was proposed; a concentric cylinder formed by smectic layers, on which the c-director of the W-shaped molecules form screw-like and/or polar arrangements.[33] The SmX phase is distinctly different from the B4 phase, as evidenced by the texture and XRD observations. Upon cooling the cell from Iso, a smectic phase (designated as SmX) appears at 185.5 1C as an optically visible filament growth. All the evaluations were carried out at RT and atmospheric pressure
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