Photo-switching behaviour in liquid crystalline materials incorporating a non-planar dithienylcyclopentene core and their birefringence properties

ABSTRACT

Reversible photochromic phase transition of non-planar dithienylcyclopentene-containing liquid crystalline molecules has been studied in this work. All materials showed the smectic A and nematic phases in the cooling process and had reversible and high interconversion yield >90% between colourless-open/blue-closed isomers in the liquid crystalline state as well as in solution by UV- and visible light-irradiation alternatively, as confirmed by nuclear magnetic resonance spectroscopy, polarised optical microscopy, differential scanning calorimetry, powder X-ray diffraction and UV-visible spectroscopy. The thermal stability of both isomers also ensures that they can maintain liquid crystalline phases during ring-open and ring-closure reactions. Their birefringence is between 0.1 and 0.2, which is comparable to that of standard liquid crystalline materials used in optical applications.

KEYWORDS:

• Photochromic
• dithienylcyclopentene
• liquid crystals

Acknowledgments

We acknowledge the support and encouragement of Prof. Keiki Kishikawa at Chiba University. This work was supported by the Ministry of Science and Technology of Taiwan [MOST 110-2113-M-027-009-] and [MOST 107-3017-F-027-001], JSPS KAKENHI JP20K21154, JP19H02581, and MEXT LEADER Programme.

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No potential conflict of interest was reported by the author(s)

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Funding

This work was supported by the JSPS [JP19H02581,JP20K21154], Ministry of Science and Technology, Taiwan [MOST 107-3017-F-027-001,MOST 110-2113-M-027-009].