Unusual Actuation of Precisely Designable Two-Layer Poly(N-isopropylacrylamide) Gel Films Composited with Asymmetrically Aligned Liquid Crystalline Nanosheets

Hierarchical structures comprising anisotropic units are the keys to realize functional materials that mimic extraordinary functions of natural systems. In this study, we established the synthesis of composite poly(N-isopropylacrylamide) gel films in which liquid crystalline (LC) inorganic nanosheets are organized into asymmetric hierarchical structures and two-layer structures with gradients. Small-angle X-ray scattering and crossed-polarizer observations confirmed the alignment of the nanosheets along the gravity and electric field applied during the synthesis. Macroscopic two-layer structures were formed in the gel films by utilizing isotropic/LC phase separation under gravity in a precisely controlled manner. By configuring the electrode arrangement and optimizing the duration and intensity of electric field application, two-layer gel films with various anisotropic and asymmetric structures such as saddle-like ones were obtained. The anisotropic two-layer structure composite gels exhibited large and fast three-dimensional deformations triggered by temperature changes with controlled curvature and anisotropic/asymmetric deformation modes as programmed by the regulated superstructures of the embedded nanosheets.

Automated summary

In this study, a method for synthesizing composite polymer gel films with hierarchical structures of liquid crystalline nanosheets was established. Different anisotropic and asymmetric structures of two-layer gel films can be obtained by controlling the electrode arrangement, duration, and intensity of the electric field. The anisotropic two-layer structure composite gels exhibit large and fast three-dimensional deformations triggered by temperature changes.