【論文】”On the origin of elasticity and heat conduction anisotropy of liquid crystal elastomers at gigahertz frequencies”

【論文】”On the origin of elasticity and heat conduction anisotropy of liquid crystal elastomers at gigahertz frequencies”

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物質理工学院 森川淳子教授George Fytas博士(前WRHI特任教授)の共著論文

“On the origin of elasticity and heat conduction anisotropy of liquid crystal elastomers at gigahertz frequencies”

が、Nature Communications に掲載されました。(DOI: 10.1038/s41467-022-32865-1

詳しくはこちら

 

<要旨>

光と物質の相互作用の偏光解析を、減衰全反射(ATR)装置とTHz周波数の放射光源を用いて、光近接場に拡張し、新しい位相・振幅マッピング技術による赤外-テラヘルツ帯の吸収異方性と複屈折を同時に測定する方法を開発した。エバネッセント4角偏光法は、30-1000cm-1 THz-IRスペクトルウィンドウの偏光子-アナライザー測定を生分解性高分子であるポリヒドロキシブチレート(PHB)とポリL乳酸(PLLA)の球晶試料に適用して実現した。ATRプリズムの面内回転を加えることで、試料の3次元異方性を全て決定することができ、このような偏光トモグラフィーは、他のスペクトル領域にも拡張できる可能性がある。

<abstract>

Liquid crystal elastomers that offer exceptional load-deformation response at low frequencies often require consideration of the mechanical anisotropy only along the two symmetry directions. However, emerging applications operating at high frequencies require all five true elastic constants. Here, we utilize Brillouin light spectroscopy to obtain the engineering moduli and probe the strain dependence of the elasticity anisotropy at gigahertz frequencies. The Young’s modulus anisotropy, E||/E~2.6, is unexpectedly lower than that measured by tensile testing, suggesting disparity between the local mesogenic orientation and the larger scale orientation of the network strands. Unprecedented is the robustness of E||/E to uniaxial load that it does not comply with continuously transformable director orientation observed in the tensile testing. Likewise, the heat conductivity is directional, κ||/κ~3.0 with κ = 0.16 Wm−1K−1. Conceptually, this work reveals the different length scales involved in the thermoelastic anisotropy and provides insights for programming liquid crystal elastomers on-demand for high-frequency applications.