Shape-transformative materials that can autonomously adopt three-dimensional (3D) shapes in response to environmental stimuli are of interest for the development of sensors and soft robotics. We herein report a new synthetic strategy to fabricate shape-transformable Eu3+-containing interpenetrating polymer films consisting of poly­(vinyl alcohol) (PVA) and poly­(3-iminodiacetate-2-hydroxypropylmethacrylate-co-acrylic acid) (P­(IDHPMA-co-AA)). Given the dynamic nature of Eu3+-iminodiacetate (IDA) coordination, ink patterning and water/Fe3+ diffusion are used to generate the in-plane or z-directional heterogeneities of Eu-IDA dynamic coordination in the polymer film, respectively. The heterogeneities can be visualized by the distribution of fluorescence emission of Eu3+. When subjected to high humidity, the differences in the swelling ratio and modulus as a result of chemical inhomogeneity further drive various 3D shape morphings, including rolling, helixing, twisting, surface buckling, and folding. Shape transformation is reversible upon the removal of moisture from the polymer films. The ink concentration and environmental humidity are demonstrated to impact the shape transformation kinetics and the final 3D shape along with other geometric parameters. Our work illustrates a novel way to fabricate new-generation biomimetic actuators and sensors.

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New self-powered hydrogels that reversibly change electrical signals in response to circumambient multistimuli are of interest for the development of the next-generation smart sensing devices. In this work, a new...

Crack resistance of rubbers is of vital importance in many applications (e.g., tire and shock absorber). In this work, we demonstrate the crack resistance improvement and toughening of natural rubber-solution polymerized butadiene styrene rubber (NR-SSBR) blend by designing a filler network composed of graphene (GE). The well-dispersed GE nanosheets contact with each other and bridge the adjacent GE nanosheets based on the π-π conjugation interaction, which preferentially break upon deformation and dissipate energy before the failure of the materials. The mechanisms of energy dissipation under small and large strains were further discussed. The approach of crack-tip morphology monitoring was also applied to understand the crack resistance behavior of the rubber material. The GE network and its energy dissipation not only increase the tensile strength and toughness, but also enhance the crack resistance of the NR-SSBR by expanding the tear energy region of high cracking energy dissipation. Improvement on these properties will provide the rubber blend with better long-term sustainability in practical applications.

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