Shape memory polymers (SMPs) have attracted significant attention and hold vast potential for diverse applications. Nevertheless, conventional SMPs suffer from notable shortcomings in terms of mechanical properties, environmental stability, and energy density, significantly constraining their practical utility. Here, inspired by the structure of muscle fibers, we report an innovative approach that involves the precise incorporation of subtle, permanent cross-linking within a hierarchical hydrogen bonding supramolecular network. This novel strategy has culminated in the development of covalent and supramolecular shape memory polyurea (CSSMP), which exhibits exceptional mechanical properties, including high stiffness (1347 MPa), strength (82.4 MPa), and toughness (312.7 MJ m-3), ensuring its suitability for a wide range of applications. Furthermore, it boasts remarkable recyclability and repairability, along with excellent resistance to moisture, heat, and solvents. Moreover, the polymer demonstrates outstanding shape memory effects characterized by a high energy density (24.5 MJ m-3), facilitated by the formation of strain-induced oriented nanostructures that can store substantial amounts of entropic energy. Simultaneously, it maintains a remarkable 96% shape fixity and 99% shape recovery. This delicate interplay of covalent and supramolecular bonds opens up a promising pathway to the creation of high-performance SMPs, expanding their applicability across various domains. This article is protected by copyright. All rights reserved.

Ultra-highly stiff and tough shape memory polyurea with unprecedentedenergy density by precise slight cross-linking.

A novel concept of developing multi-principal elements, or compositional complex alloys is referred as high-entropy alloys (HEAs). This review addresses the role of entropy in alloying additions along with the effect of various elements listed in the periodic table in forming the HEAs. Phase formation rules and the associated parameters along with their significance are discussed. The physical metallurgy technique is elaborated with reference to the high-entropy effect, severe lattice distortion effect, sluggish diffusion effect, and cocktail effects. Various types of HEAs such as light weight HEAs, nanoprecipitate HEAs, ultrafine-grained HEAs, dual-phase HEAS and TRIP/TWIN HEAs are discussed. Further, the effects of mechanical alloying in HEAs are presented. Finally, the microstructural effects and mechanical properties of HEAs are addressed with reference to the published literature. 

Development of high entropy alloys (HEAs): Current trends

Polymeric materials capable of spontaneously healing physical damages and restoring various functions have been attracting growing interest. Among these, the category of water‐insensitive self‐healing materials emerges as a promising research focus due to their reliable self‐healing and stable mechanical properties in high‐humidity environments and even underwater. In this review, an update on the significant advancements in the design of water‐insensitive self‐healing polymers is presented, which are based on various unique chains. Their advantages and limitations are discussed. Additionally, a series of typical dynamic interactions that are used to enable autonomous self‐healing in underwater environments is highlighted. Moving beyond these fundamental designs, the diverse opportunities to leverage recent synthetic advancements in water‐insensitive self‐healing materials for the progression of soft electronic applications are systematically discussed. Ultimately, the significant challenges and remaining opportunities to present a comprehensive view of the future development of water‐insensitive self‐healing materials are highlighted. This review aims to stimulate further innovation in this burgeoning and emerging field of intrinsic healable materials, interfacing with dynamic chemistry and soft electronics.

Water‐Insensitive Self‐Healing Materials: From Network Structure Design to Advanced Soft Electronics

Multifunctional high-entropy materials

Abstract In the face of ubiquitous corrosion threats, the development of high-performance elastomer protective materials with active self-healing functions is extremely challenging and significant. We propose an approach by combining WPU elastomer with GO to create the multifunctional pearl layer structured polymers with interface hydrogen bonds. By crosslinking the polycaprolactone diol (PCL) chain with a hydrogen bond array, the elastomer with high mechanical strength, extensibility, elasticity, excellent damage resistance, and healing properties was successfully synthesized. The elastomer exhibits remarkable mechanical properties, including a tensile strength of 39.89 MPa, toughness value of 300.3 MJ m −3 , and fracture energy of 146.57 kJ m −2 . The enhanced damage resistance of the elastomer can be attributed to the decomposable hydrogen bond array as well as the strain-induced crystallization of PCL fragments, which effectively dissipate energy. Importantly, due to the reversibility of the hydrogen bonding array, the fractured WPU can easily heal and restore its original mechanical properties when subjected to heating at 50 °C. Moreover, the photothermal properties of GO enable the biomimetic polymer coating to achieve damage recovery after being irradiated with NIR for 30 s. The obtained biomimetic coating exhibits a highly oriented lamellar structure, thereby greatly enhancing physical barrier performance and anti-corrosion performance. Electrochemical impedance spectroscopy (EIS) shows that the impedance modulus is one order of magnitude higher than that of the blank coating. Additionally, scanning vibrating electrode (SVET) confirmed that the self-healing performance and protection effect of the biomimetic coating in 3.5 wt% NaCl solution were also reliable. This highly reliable biomimetic coating presents a revolutionary solution for creating multi-functional, high-performance smart material in harsh environments. 

Bio-inspired self-healing and anti-corrosion waterborne polyurethane coatings based on highly oriented graphene oxide

Supramolecular plastics (SMPs) can be made mechanically robust, repairable, and recyclable, rendering themselves promising alternatives to their conventional predecessors to address environmental concerns. However, dense accumulations of noncovalent bonds generally lead to mechanical brittleness as well as intolerance toward heat and moisture. To resolve this issue, a simple strategy of preparing high‐performance SMP by constructing highly dense, but irregular hydrogen‐bond networks with hierarchical structures is proposed. The resultant SMP exhibits an outstanding combination of good comprehensive mechanical properties (high stiffness, strength, and toughness with ductile failure when fracturing), excellent dynamic behaviors (repairability and recyclability), and high tolerances toward moisture and high temperatures (as high as 90 °C). Additionally, the SMP also shows a high dielectric constant, exhibiting great potential for applications such as healable flexible touch screens and energy storage. Last, through structure characterizations and molecular dynamic simulation, this study provides a fundamental insight into the mechanism behind such high‐performances from nano‐ to micro‐scales, which is expected to inspire the design of a wide range of other SMPs that use different chemistries.

Transparent High‐Performance Supramolecular Plastics Operating in All‐Weather Environments

Utilization of coal gangue powder to improve the sustainability of ultra-high performance concrete

Comprehensive Performance of Polyimide Reinforced by Multiple Hydrogen Bonds for Flexible Electronics Application

It is challenging to achieve good combinations of excellent mechanical properties and low coercivity (≤200 A/m) in typical soft magnetic alloys. In this work, TiC/Fe24Ni24Co24Mn18 high-entropy composite (HEC) prepared by mechanical alloying (MA) and spark plasma sintering (SPS) was produced to achieve good combinations of strength-ductility synergy and low coercivity. After MA, the TiC/Fe24Ni24Co24Mn18 HEC powders were composed of a main face-centered cubic (fcc) phase and some body-centered cubic (bcc) phase. Following SPS, the bulk TiC/Fe24Ni24Co24Mn18 HEC consisted of a fcc phase with nanosized TiC. In detail, the HEC showed multilevel heterogeneous microstructure, i.e., ultra-fine fcc grains (∼0.38 µm), micron-sized fcc grains (∼1.49 µm), and uniform dispersion of the in-situ formed TiC nanoparticles (∼98 nm) in ultra-fine fcc grains. The bulk TiC/Fe24Ni24Co24Mn18 HEC exhibits a high tensile yield strength of ∼1167 MPa and an exceptionally low coercivity of ∼100.5 A/m, suggesting an outstanding combinations of mechanical and magnetic properties. Compared with previously reported Fe-Co alloys or high entropy alloys (HEAs), the TiC/Fe24Ni24Co24Mn18 HEC shows a significantly enhanced yield strength while maintaining a relatively low coercivity, primarily resulting from the heterogeneous microstructure caused by the in-situ formed TiC. 

Microstructure and properties of TiC/Fe24Ni24Co24Mn18 high-entropy composite with exceptionally low coercivity

Antioxidants are molecules that can prevent the harmful effects of oxygen, help capture and neutralize free radicals, and thus eliminate the damage of free radicals to the human body. Persimmon tannin (PT) has excellent antioxidant activity, which is closely related to its molecular structure. We report here a comparative study of four characteristic structural units from PT (epicatechin gallate (ECG), epigallocatechin gallate (EGCG), A−type linked ECG dimer (A−ECG dimer), A−type linked EGCG dimer (A−EGCG dimer)) to explore the structure–activity relationship by using the density functional theory. Based on the antioxidation mechanism of hydrogen atom transfer, the most favorable active site for each molecule exerts antioxidant activity is determined. The structural parameters, molecular electrostatic potential, and frontier molecular orbital indicate that the key active sites are located on the phenolic hydroxyl group of the B ring for ECG and EGCG monomers, and the key active sites of the two dimers are located on the phenolic hydroxyl groups of the A and D’ rings. The natural bond orbital and bond dissociation energy of the phenolic hydroxyl hydrogen atom show that the C11−OH in the ECG monomer and the C12−OH in the EGCG monomer are the most preferential sites, respectively. The most active site of the two A−linked dimers is likely located on the D’ ring C20′ phenolic hydroxyl group. Based on computational analysis of quantum chemical parameters, the A−ECG dimer is a more potent antioxidant than the A−EGCG dimer, ECG, and EGCG. This computational analysis provides the structure–activity relationship of the four characteristic units which will contribute to the development of the application of PT antioxidants in the future.

https://www.mdpi.com/1996-1944/16/1/320/pdf?version=1672303833

Computational Analysis on Antioxidant Activity of Four Characteristic Structural Units from Persimmon Tannin

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