Liquid crystalline elastomers (LCEs) combine high anisotropy with good flexibility, and exhibits excellent stimuli-responsive capability and large shape transformations. Nowadays, LCEs have widely applied to soft robots, artificial muscle, smart coating and other emerging areas, owing to their outstanding performances. However, common stimulus (e.g. temperature and humidity) as switch or trigger, are slow and hard to control. Herein, a novel asymmetrically fluorine-substituted azobenzene dopant was designed and synthesized, and doped into the nematic liquid crystal matrix to construct photoelectric-responsive LCEs for precise control. Particularly, the rigid axis of the dopant does not fit with its polar axis, leading to negative dielectric anisotropy (Δε=-4.05). Naturally, the doped LCE also possesses good negative dielectric anisotropy (Δε=-1.49 at room temperature). As a direct current electric field with the field strength of 1 V/μm was applied, the obtained LCE flake bended 30° within 2 seconds. On the other hand, the LCE flake underwent rapid reversible deformation under ultraviolet and visible photoirradiation, which attributes to the photoisomerization of azobenzene group in the dopant molecules. Clearly, this dual-responsive LCE offers an outstanding and promising control strategy for smart soft matter.

Photoelectric-responsive liquid crystal elastomer for rapid, controllable, and reversible deformation

ACS Spring 2022

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