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Updated: Sep 16, 2025

Novel Techniques for Observing Structural Dynamics of Photoresponsive Liquid Crystals
Published on: May 29, 2018
Light-Driven Crystal Actuation of Fluorinated Acylhydrazones Enabled by [2+2] Photocycloaddition
Jinbo Ouyang1, Longping Jiang1, Jiayao Li1
1Jiangxi Province Key Laboratory of Functional Organic Polymers, School of Chemistry and Materials Science, East China University of Technology, Nanchang, 330013, China.
Abstract:
Crystalline materials with photomechanical responsiveness have garnered significant attention in flexible actuators and micro/nano-electromechanical systems due to their unique capability to directly convert light into mechanical energy. In this work, four novel fluorinated acylhydrazone compounds were successfully synthesized through direct condensation reactions between 4,4'-difluorobenzophenone (DFBP) and acylhydrazine compounds, including benzoylhydrazine (BHD), 3-fluorobenzoylhydrazine (3-FBHD), isoniazid (IND), and acetylhydrazine (AED). Systematic investigation of their photomechanical responses revealed distinct molecular mechanisms. Experimental results demonstrate that isomeric fluorinated acylhydrazone derivatives (DFBP-BHD, DFBP-3-FBHD, DFBP-IND) exhibit dynamic photo-responsive behavior ranging from crack initiation to crystal fragmentation under 365 nm UV irradiation, whereas the hydrazone derivative DFBP-AED remains inert. This confirms the essential role of [2 + 2] photocycloaddition-dependent C = N double bonds in photomechanical activity. Comprehensive characterization through DSC, TG, XRD, ¹H/¹3C NMR, and MS elucidated the formation pathways and structural characteristics of photocycloaddition products. Density functional theory calculations revealed that energy disparities between (0 0 1) and (1 0 0) crystallographic planes govern longitudinal fragmentation patterns. This study establishes a "molecular structure-crystal arrangement-macroscopic response" multi-scale regulation strategy, offering novel insights for developing high-performance light-driven materials.
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