Electric-field-induced deformation of liquid crystalline elastomers with flexoelectric polarization

2023 Fiscal Year Final Research Report

• Project/Area Number: 20K05654
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 35030:Organic functional materials-related
• Research Institution: Tokyo Polytechnic University
• Principal Investigator: Hiraoka Kazuyuki 東京工芸大学, 工学部, 教授 (50267530)
• Project Period (FY): 2020-04-01 – 2024-03-31
• Keywords: 液晶エラストマー / 液晶 / 高分子 / フレクソエレクトリック効果 / 自発分極 / ネマチック液晶 / 広がり変形 / 曲がり変形

Outline of Final Research Achievements

Flexoelectric polarization was investigated in liquid crystalline elastomers composed of wedge-shaped mesogens prepared in cross-linking under uniaxial deformation, under horseshoe-shaped deformation, and under shear deformation. X-ray diffractometry revealed that the orientational order remained at about S = 0.2 even in the temperature region of the isotropic phase designated tentatively as the pseudo-isotropic phase. In addition, X-ray diffractometry also revealed that splay distortion of director was induced in uniaxially deformed and shear deformed elastomers, and that bend distortion occurred in the horseshoe-shaped deformed elastomer. The electric charge due to the flexoelectric effect was confirmed in the pseudo-isotropic phase of these elastomers, while almost no electric charge was observed in the smectic A phase. We concluded that the macroscopic polarization due to the flexoelectric effect was fixed in the liquid crystalline elastomers with splay and/or bend distortion.

Free Research Field

化学

Academic Significance and Societal Importance of the Research Achievements

変形過程下（引っ張り変形、馬蹄変形、せん断変形）において架橋することで、配向ベクトルが広がり変形状態もしくは曲がり変形状態で固定され、フレクソエレクトリック効果による分極を有する液晶エラストマーを得る方法を確立した。この人工的な自発分極を持つエラストマーは、アクチュエーターや人工筋肉用材料として期待される。
ビベンゾエートをメソゲンとする主鎖型液晶エラストマーを8.7倍延伸した試料を作成し、延伸倍率により配向方向が90°回転することを見出した。この新たな配向回転は、今後の機能性有機材料の開発研究に有益な基礎科学的な知見である。