The tensile and frictional properties required for each use of polymer film are different. The arrangement of mesogenic units determines mechanical characteristics of the liquid crystal polymer network (LCN) film. In this work, by modulating mesogenic unit patterns of LCN film, the tensile strength and stimuli-responsive friction are finely controlled. Applying a three-dimensional electric field with crossed electrodes generates periodic topological defects in the LCN films. Toughness and ductility are enhanced as the number of defects increases in a given area, which is related to the heterogeneity of elastic modulus that hinders crack propagation. Furthermore, the micro-patterned LCN film is deformed to show dimple arrays in response to the heat. The deformative behavior of the film is analyzed and predicted by calculating the activation force density. This topographical change of the LCN film in high temperature decreases the dynamic friction coefficient with a flat glass due to the reduction of effective contact area. In our platform, the pattern of mesogenic units can be diversified into dozens by changing the applied electric field configuration. This work demonstrates a novel strategy to control the tensile and frictional properties of polymer film to be optimized on-demand for industrial application such as polymer coating films, soft robotics, soft actuators and artificial muscles.

Tuning mechanical properties of liquid crystal polymer network with topological defect array

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