Unveiling Low THz Dynamics of Liquid Crystals: Identification of Intermolecular Interaction among Intramolecular Modes

Liquid crystals have found a wide area of application over the last few decades, proving to be excellent materials for tunable optics from visible to near-infrared frequencies. Currently, much effort is devoted to demonstrating their applicability at THz frequencies (1–10 THz), where tremendous adva...

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Bibliographic Details
Published in:The journal of physical chemistry. B 2024-01, Vol.128 (2), p.596-602
Main Authors: Friebel, Patrick, Galimberti, Daria Ruth, Savoini, Matteo, Cattaneo, Laura
Format: Article
Language:English
Subjects:
B: Soft Matter, Fluid Interfaces, Colloids, Polymers, and Glassy Materials
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Summary:Liquid crystals have found a wide area of application over the last few decades, proving to be excellent materials for tunable optics from visible to near-infrared frequencies. Currently, much effort is devoted to demonstrating their applicability at THz frequencies (1–10 THz), where tremendous advances of broadband and intense sources have been achieved. Yet, a detailed understanding of THz-triggered dynamics in liquid crystals is incomplete. Here, we perform broadband THz time domain spectroscopy on 4-cyano-4′-alkyl-biphenyl (nCB) and 5-phenylcyclohexanes (PCH5) across mesophases. Density functional theory calculations on isolated molecules capture the majority of the response. In particular, the pronounced modes around 4.5 and 5.5 THz mainly originate from bending modes of the cyano group. In contrast, the broad response below 3 THz, linked to modes of the alkyl chain, disagrees with the single molecule calculation. Here, we identify a clear intermolecular character of the response, supported by dimer and trimer calculations.
ISSN:1520-6106
1520-5207
DOI:10.1021/acs.jpcb.3c07947