It is challenging to develop materials with roomtemperature self-healing ability and mechanochromic response from mechanical stimuli to optical signals by a facile and simple preparation process. Herein, novel mechanochromic self-healing materials were designed by a simple synthesis procedure, balancing the mechanical properties, self-healing, stretchability, and mechanochromic response. Moreover, we designed and prepared the mechanochromic self-healing materials with different soft and hard segments by introducing multiple hydrogen bonds into the network, improving the mechanical properties and self-healing efficiency. In addition, the optimized sample exhibited good shape memory behavior (shape recovery ratio of 94.4%), self-healing properties (healed by pressing during stretching process), high tensile strength (17.6 MPa), superior stretchability (893%), fast mechanochromic response (strain of 272%), and great cyclic stretchingrelaxing properties (higher than 10 times at strain of 300%). Above all, mechanochromic self-healing materials have promising potential in various fields, such as stress sensing, inkless writing, damage warning, deformation detection, and damage distribution.
The authors are motivated to develop a series of hydrochromic copolymers with fast response, reversibility, repeatability, and visual transparency transition. The hydrochromic block copolymers are based on the rational ratio of hydrophilic segments of poloxamer block and hydrophobic segments of ethyl cellulose according to the preparation method of polyurethane. By tuning the ratio of hydrophilic segments or adding hygroscopic salts, the hydrochromic polymer is endowed with the ability to visualize the transparency in response to the relative humidity. Especially, the response time of the polymer is extremely shortened, up to 1 s for the optimized sample. Within the moisture stimulation, the hygroscopic swelling increases the film thickness, leading to a reversible transparency switching from a highly transparent state (82%) to an opaque white state (20.5%).
Herein, a novel NH2–MIL–53(Fe)/polypyrrole@cellulose fiber (NMF/PPy@CelF) composite was prepared based on cellulose fiber (CelF) by a double in-situ growth method, consisting of polypyrrole (PPy) and NH2–MIL–53(Fe) (NMF). The interfacial photocatalysis and photothermal properties of the obtained composite was systematically evaluated by treating 20 ml·L− 1 methylene blue (MB) sulotion under 1 kW·m− 2 illumination. The NMF/PPy@CelF composite showed good photocatalytic activity with a degradation rate of 76.90% of MB within 180 min. Moreover, the photothermal conversion efficiency of NMF/PPy@CelF reached 92.16%. The PPy layer not only improved the visible light absorption range and interfacial temperature of the composite, but also facilitated the separation of photoelectrons and holes, endowing the NMF/PPy@CelF composite with good photothermal and photocatalytic properties. Furthermore, superior stability of the NMF/PPy@CelF composite was observed in repeated cycles. In addition, the photocatalytic mechanism was proposed. This work combines the photothermal effect with solar-driven photocatalysis, simultaneously achieving complete degradation of dyes and the recovery of clean water from dye wastewater.
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