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Polymerizable deep eutectic monomers (DEMs) were prepared by mixing various molar ratios of acrylamide (AM) and choline chloride (ChCl). 1H NMR and Fourier transform infrared confirmed that there were strong hydrogen bonds between AM and ChCl in DEMs. The hydrogen bonds can effectively depress the crystallization of AM and ChCl. All DEMs can be used for sustainable thermal-induced frontal polymerization (FP) at 35 °C. It was found ChCl could accelerate the FP of DEMs. The front velocity (V f) and the maximum front temperature (T max) of FP in DEM were much higher than those in dimethyl sulfoxide. The increase in the molar ratio of AM and ChCl and the amount of N,N′-methylenebisacrylamide (MBA) led to an increase in V f and T max. When the polymerized DEM hydrogels were immersed in distilled water, water-soluble ChCl were washed out and the hydrogels were further freeze-dried. The macroporous polyacrylamide hydrogels with pores in an average diameter of about 150 μm were observed. They exhibited superfast reversible swelling and shrinkage in alternate water and acetone. The study implies a facile and green method to efficiently fabricate macroporous polyacrylamide hydrogels with superfast responsive properties via FP of DEMs in less than 6 min. The preparation method is also green, low-energy, and sustainable and possesses a good application prospect in the environmental and biomedical areas.

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The effect of cyclic thermal loading on the microstructure and thermoelectric properties of CoSb 3 was investigated. The microstructures of the samples were characterized by x-ray diffractometry, scanning electron microscopy, energy dispersive x-ray spectrometry and density measurements. The electrical conductivity, the Seebeck coefficient and the thermal conductivity were measured from room temperature to 800 K. Under cyclic thermal loading, antimony partially volatilized from the surface of the sample, and the density obviously decreased. After 2000 cycles, the phase composition of the sample remained stable, and the average grain size did not change significantly. Moreover, the electrical conductivity varied only slightly, except in the low temperature region. The Seebeck coefficient decreased slightly. However, the thermal conductivity changed remarkably with increasing numbers of thermal cycles.

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We demonstrate an effective approach to enhance the output performance of a flexible piezoelectric energy harvester by using flexible electrodes with negative Poisson's ratio (NPR). The relationship between open-circuit voltage and Poisson's ratio of electrodes is established theoretically by deriving the analytical expression. It reveals a continuous increasing trend in open-circuit voltage with the decrease in Poisson's ratio of the electrodes. Further, graphene-assembled macro-film (GAMF), an NPR material with excellent flexibility and high conductivity, is used as the electrodes to fabricate flexible piezoelectric energy harvesters. Compared with the energy harvesters using silver electrode, the harvesters made by GAMF electrodes, with an NPR of −0.39, achieve nearly 1.7-times enhancement in open-circuit voltage and 1.6-times in short-circuit current for output performance. The experimental results are highly consistent with the simulation results, indicating that the GAMF has great prospects in developing flexible piezoelectric energy harvesters with enhanced electrical output performance.