Polymer dielectrics are highly desirable in capacitor applications due to their low cost, high stability, and reliability. However, there still remains a lack of feasible methods to prepare polymer dielectrics with high energy density and low dielectric loss, which severely hampers the development of compact and efficient power electronics. Here, an amphiphilic block copolymer, polythiourea‐b‐polydimethylsiloxane (PTU‐b‐PDMS), with an extraordinarily high energy density of 29.8 J cm−3 and a low loss is synthesized via polyaddition polymerization. This is highly relevant to the block molecule conformation in the interfacial region of the self‐assembled PTU‐b‐PDMS. The block molecule in the interface adopts an extended conformation when the PTU forms nanodots, whereas the block molecule adopts a coiled conformation when the PTU forms nanostrands. The observation and characterization have proved that the coiled block molecule in the interfacial region can simultaneously induce extra strong charge trapping sites and dipolar polarization. It substantially improves the breakdown strength from 652 to 1166 MV m−1, while maintaining a high dielectric constant of 5 and a low loss of <0.01. This work offers unprecedented structural insights into the conformation‐induced interfacial effect and enables rational design of self‐assembled copolymers to boost their dielectric properties and energy density.

An ionic liquid was used in this work to dissolve rice straw at 90 °C to explore the dissolution of cellulose, lignin, and hemicellulose in the straw at different treatment times. Compared with traditional methods, the method involved short time and high efficiency. The residual amounts of multiple substances were evaluated at different time periods. The results showed that the dissolution rate of triglyceride fats, water-soluble pectin, and lignin reached their maxima at 10 min, after which the dissolution rates decreased. Because lignin is wrapped as an outer layer surrounding cellulose and becomes dissolved in preference to hemicellulose and cellulose, cellulose and hemicellulose dissolve minimally at the beginning of the reaction, and the dissolution rate is slow. This study showed that there is a certain possibility for the direct utilization of ionic liquids for the treatment of straw biomass.

The wetting property of a solid surface has been a hotspot for centuries, and many studies suggest that the hydrophobicity is highly related to the polar components. However, the underlying mechanism of polar moieties on the hydrophobicity remains unclear. Here, we tailor the surface polar moieties of epoxy resin (EP) by ozone modification and assess their wetting properties. Our results show that, for the modified EP with more (60.54%) polar moieties, the polar effect on hydrophobicity cannot be empirically observed. To reveal the underlying mechanism, the absorption parameters, including equilibrium distance, adsorption radius, and effective adsorption sites for water on EP before and after ozone treatment, are calculated on the basis of molecular simulations. After ozone modification, the equilibrium distance (from 1.95 to 1.70 Å), adsorption radius (from 3.80 to 4.50 Å), and effective adsorption sites (from 1 to 2) change slightly and the EP surface remains hydrophobic, although the polar groups significantly increase. Therefore, it is concluded that the wetting properties of solid surfaces are dominated by the equilibrium distance, adsorption radius, and effective adsorption sites for water on solids, and the nonlinear relationship between polar groups and hydrophilicity is clarified.

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Back Cover: In article number 2100700 by Yang Feng, Shengtao Li, and co‐workers, a new amphiphilic block copolymer with clear phase separation shows an extraordinarily high energy density of 29.8 J cm−3. This is because the coiled block molecule in the interfacial region can substantially improve the breakdown strength from 652 MV m−1 to 1166 MV m−1, while maintaining a high dielectric constant of 5 and a low loss of <0.01.