Development of twist-bend nematic liquid crystals using sulfur and selenium linkages

2022 Fiscal Year Final Research Report

• Project/Area Number: 20K15351
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 35030:Organic functional materials-related
• Research Institution: Toyohashi University of Technology
• Principal Investigator: Arakawa Yuki 豊橋技術科学大学, 工学(系)研究科(研究院), 助教 (30757365)
• Project Period (FY): 2020-04-01 – 2023-03-31
• Keywords: ツイストベンドネマチック相 / 二量体液晶 / 三量体液晶 / 硫黄 / チオエーテル / セレン / セレノエーテル

Outline of Final Research Achievements

With the aim of establishing new molecular design for the heliconical twist-bend nematic (NTB) phase, we synthesized, for the first time, sulfur- and selenium-linked bent-shaped liquid crystal (LC) dimers and trimers. The idea is based on smaller bond angles and more flexibility of thioether (C-S-C) and selenoether (C-Se-C) compared with methylene (C-CH2-C) and ether (C-O-C) for more bent shape. A number of thioether- and selenoether-linked dimers and trimers consisting of two mesogenic arms such as cyanobiphenyl, azobenzene, and N-benzylideneaniline were synthesized. It was revealed that thioether and selenoether linkages are very useful in the formation and stabilization of the NTB phase. Remarkably, many LC dimers exhibited the NTB phase that were stable down to room temperature and vitrified. In addition, helical periodic pitches and unique viscoelastic properties of certain dimers were also clarified.

Free Research Field

液晶化学

Academic Significance and Societal Importance of the Research Achievements

チオエーテル(C-S-C)およびセレノエーテルは(C-Se-C)は、汎用的なメチレン(C-CH2-C)やエーテル(C-O-C)と比較して小さな結合角および長い結合長により嵩高い置換基となるため、液晶相の形成には不利となることが多い。一方で本研究は、チオエーテルおよびセレノ―エーテルが、ツイストベンドネマチック(NTB)相の形成および安定化にメチレンおよびエーテルよりも優れることを明らかにした。特に、多くの二量体が室温以下までNTB相およびそのガラス状態を保持できる点は従来の二量体を凌駕する特徴の一つである。また、本研究は硫黄およびセレンの有効利用にもつながる点でも社会的な意義がある。