Self‐healing ability is an important survival feature in nature, with which living beings can spontaneously repair damage when wounded. Inspired by nature, people have designed and synthesized many ...self‐healing materials by encapsulating healing agents or incorporating reversible covalent bonds or noncovalent interactions into a polymer matrix. Among the noncovalent interactions, the coordination bond is demonstrated to be effective for constructing highly efficient self‐healing polymers. Moreover, with the presence of functional metal ions or ligands and dynamic metal–ligand bonds, self‐healing polymers can show various functions such as dielectrics, luminescence, magnetism, catalysis, stimuli‐responsiveness, and shape‐memory behavior. Herein, the recent developments and achievements made in the field of self‐healing polymers based on coordination bonds are presented. The advantages of coordination bonds in constructing self‐healing polymers are highlighted, the various metal–ligand bonds being utilized in self‐healing polymers are summarized, and examples of functional self‐healing polymers originating from metal–ligand interactions are given. Finally, a perspective is included addressing the promises and challenges for the future development of self‐healing polymers based on coordination bonds.
Coordination bonds have been demonstrated to be effective for constructing self‐healing polymers in recent years. The advantages of coordination bonds in constructing self‐healing polymers are discussed, and the various metal–ligand bonds being utilized in self‐healing polymers along with some examples of functional self‐healing polymers originating from metal–ligand interactions are summarized. A few concerns and future directions in this research field are proposed.
There is often a trade-off between mechanical properties (modulus and toughness) and dynamic self-healing. Here we report the design and synthesis of a polymer containing thermodynamically stable ...whilst kinetically labile coordination complex to address this conundrum. The Zn-Hbimcp (Hbimcp = 2,6-bis((imino)methyl)-4-chlorophenol) coordination bond used in this work has a relatively large association constant (2.2 × 10
) but also undergoes fast and reversible intra- and inter-molecular ligand exchange processes. The as-prepared Zn(Hbimcp)
-PDMS polymer is highly stretchable (up to 2400% strain) with a high toughness of 29.3 MJ m
, and can autonomously self-heal at room temperature. Control experiments showed that the optimal combination of its bond strength and bond dynamics is responsible for the material's mechanical toughness and self-healing property. This molecular design concept points out a promising direction for the preparation of self-healing polymers with excellent mechanical properties. We further show this type of polymer can be potentially used as energy absorbing material.
Achieving a desirable combination of solid-like properties and fast self-healing is a great challenge due to slow diffusion dynamics. In this work, we describe a design concept that utilizes weak but ...abundant coordination bonds to achieve this objective. The designed PDMS polymer, crosslinked by abundant Zn(II)-carboxylate interactions, is very strong and rigid at room temperature. As the coordination equilibrium is sensitive to temperature, the mechanical strength of this polymer rapidly and reversibly changes upon heating or cooling. The soft-rigid switching ability σ, defined as G'
/G'
, can reach 8000 when ΔT = 100 °C. Based on these features, this polymer not only exhibits fast thermal-healing properties, but is also advantageous for various applications such as in orthopedic immobilization, conductive composites/adhesives, and 3D printing.
Flexible electronic skins (e‐skins) play a very important role in the development of human–machine interaction and wearable devices. To fully mimic the functions of human skin, e‐skins should be able ...to perceive multiple external stimuli (such as temperature, touch, and friction) and be resistant to injury. However, both objectives are highly challenging. The fabrication of multifunctional e‐skins is difficult because of the complex lamination scheme and the integration of different sensors. The design of skin‐like materials is hindered by the trade‐off problem between flexibility, toughness, and self‐healing ability. Herein, flexible sodium methallyl sulfonate functionalized poly(thioctic acid) polymer chains are combined with rigid conductive polyaniline rods through ionic bonds to obtain a solvent‐free polymer conductive gel. The conductive gel has a modulus similar to that of skin, and shows good flexibility, puncture‐resistance, notch‐insensitivity, and fast self‐healing ability. Moreover, this conductive gel can convert changes in temperature and strain into electrical signal changes, thus leading to multifunctional sensing performance. Based on these superior properties, a flexible e‐skin sensor is prepared, demonstrating its great potential in the wearable field and physiological signal detection.
A new solvent‐free polymer conductive gel is obtained by combining flexible sulfonate‐containing poly(thioctic acid) polymer chains and rigid conductive polyaniline rods. The conductive gel shows good flexibility, puncture‐resistance, notch‐insensitivity, and fast self‐healing ability. Moreover, this conductive gel can convert changes in temperature and strain into electrical signal changes, and thus can be used for multifunctional electronic skin.
Increasing visible light absorption of classic wide‐bandgap photocatalysts like TiO2 has long been pursued in order to promote solar energy conversion. Modulating the composition and/or stoichiometry ...of these photocatalysts is essential to narrow their bandgap for a strong visible‐light absorption band. However, the bands obtained so far normally suffer from a low absorbance and/or narrow range. Herein, in contrast to the common tail‐like absorption band in hydrogen‐free oxygen‐deficient TiO2, an unusual strong absorption band spanning the full spectrum of visible light is achieved in anatase TiO2 by intentionally introducing atomic hydrogen‐mediated oxygen vacancies. Combining experimental characterizations with theoretical calculations reveals the excitation of a new subvalence band associated with atomic hydrogen filled oxygen vacancies as the origin of such band, which subsequently leads to active photo‐electrochemical water oxidation under visible light. These findings could provide a powerful way of tailoring wide‐bandgap semiconductors to fully capture solar light.
In contrast to the common tail‐like absorption band in hydrogen‐free oxygen‐deficient TiO2, an unusual strong absorption band spanning the full spectrum of visible light is achieved in red anatase TiO2 by intentionally introducing atomic hydrogen‐mediated oxygen vacancies that subsequently lead to active photo‐electrochemical water oxidation under visible light.
Owing to their high earth‐abundance, eco‐friendliness, high electrical conductivity, large surface area, structure tunability at the atomic/morphological levels, and excellent stability in harsh ...conditions, carbon‐based metal‐free materials have become promising advanced electrode materials for high‐performance pseudocapacitors and metal–air batteries. Furthermore, carbon‐based nanomaterials with well‐defined structures can function as green catalysts because of their efficiency in advanced oxidation processes to remove organics in air or from water, which reduces the cost for air/water purification and avoids cross‐contamination by eliminating the release of heavy metals/metal ions. Here, the research and development of carbon‐based catalysts in supercapacitors and batteries for clean energy storage as well as in air/water treatments for environmental remediation are reviewed. The related mechanistic understanding and design principles of carbon‐based metal‐free catalysts are illustrated, along with the challenges and perspectives in this emerging field.
The research and development of carbon‐based metal‐free catalysts in pseudocapacitors and batteries for clean energy storage, as well as in air/water treatments for environment remediation are reviewed. The related mechanistic understanding and design principles of carbon‐based catalysts are illustrated, along with the challenges and perspectives in this emerging field.
The challenges of developing neuromorphic vision systems inspired by the human eye come not only from how to recreate the flexibility, sophistication, and adaptability of animal systems, but also how ...to do so with computational efficiency and elegance. Similar to biological systems, these neuromorphic circuits integrate functions of image sensing, memory and processing into the device, and process continuous analog brightness signal in real-time. High-integration, flexibility and ultra-sensitivity are essential for practical artificial vision systems that attempt to emulate biological processing. Here, we present a flexible optoelectronic sensor array of 1024 pixels using a combination of carbon nanotubes and perovskite quantum dots as active materials for an efficient neuromorphic vision system. The device has an extraordinary sensitivity to light with a responsivity of 5.1 × 10
A/W and a specific detectivity of 2 × 10
Jones, and demonstrates neuromorphic reinforcement learning by training the sensor array with a weak light pulse of 1 μW/cm
.
Boron‐based adhesives have attracted considerable attention in recent years due to their strong adhesive behavior and reversible capacities. However, limited by the humidity sensitivity and poor ...dynamicity, it remains challenging for the boron‐based adhesive materials to realize strong and long‐term adhesion underwater. In this study, a novel boronic ester (BN‐6) with changeable ring strain induced by the heat‐responsive BN coordination bond is designed and synthesized. Due to the low strain of the six‐membered ring at ambient conditions and the high strain of the ten‐membered ring at elevated temperature, BN‐6 exhibits enhanced hydrolytic/thermal stabilities as well as dynamicity. The model dynamic crosslinking polymers containing BN‐6 linkages present significantly improved water‐resistance and recyclability. Specifically, based on the hydrolytically stable whilst kinetically active boronic ester linkage, a strong and recyclable adhesive material is successfully prepared. Long‐term adhesion performance under water and harsh conditions is realized on different substrates, with the maximum adhesion strength of 4.21 MPa. The report provides a novel chemical strategy for designing stable and dynamic boronic ester linkages and the synthesized adhesive has pioneered in the field of long‐term underwater application of boron‐based adhesives.
The authors have synthesized a novel boronic ester with enhanced hydrolytic stability and dynamicity through the reversible transition of ring strain induced by the heat‐responsive BN coordination. Therefore, the adhesive containing this boronic ester exhibits excellent adhesion strength and repeatable long‐term stability under water and harsh environments, which has broken through the bottleneck of underwater application of boron‐based adhesives.
Thioridazine (THD) is a common phenothiazine antipsychotic drug reported to suppress growth in several types of cancer cells. We previously showed that THD acts as an antiglioblastoma and anticancer ...stem-like cell agent. However, the signaling pathway underlying autophagy and apoptosis induction remains unclear. THD treatment significantly induced autophagy with upregulated AMPK activity and engendered cell death with increased sub-G1 in glioblastoma multiform (GBM) cell lines. Notably, through whole gene expression screening with THD treatment, frizzled (Fzd) proteins, a family of G-protein-coupled receptors, were found, suggesting the participation of Wnt/β-catenin signaling. After THD treatment, Fzd-1 and GSK3β-S9 phosphorylation (inactivated form) was reduced to promote β-catenin degradation, which attenuated P62 inhibition. The autophagy marker LC3-II markedly increased when P62 was released from β-catenin inhibition. Additionally, the P62-dependent caspase-8 activation that induced P53-independent apoptosis was confirmed by inhibiting T-cell factor/β-catenin and autophagy flux. Moreover, treatment with THD combined with temozolomide (TMZ) engendered increased LC3-II expression and caspase-3 activity, indicating promising drug synergism. In conclusion, THD induces autophagy in GBM cells by not only upregulating AMPK activity, but also enhancing P62-mediated autophagy and apoptosis through Wnt/β-catenin signaling. Therefore, THD is a potential alternative therapeutic agent for drug repositioning in GBM.
Abstract
Capture and conversion of CO
2
from oceanwater can lead to net-negative emissions and can provide carbon source for synthetic fuels and chemical feedstocks at the gigaton per year scale. ...Here, we report a direct coupled, proof-of-concept electrochemical system that uses a bipolar membrane electrodialysis (BPMED) cell and a vapor-fed CO
2
reduction (CO
2
R) cell to capture and convert CO
2
from oceanwater. The BPMED cell replaces the commonly used water-splitting reaction with one-electron, reversible redox couples at the electrodes and demonstrates the ability to capture CO
2
at an electrochemical energy consumption of 155.4 kJ mol
−1
or 0.98 kWh kg
−1
of CO
2
and a CO
2
capture efficiency of 71%. The direct coupled, vapor-fed CO
2
R cell yields a total Faradaic efficiency of up to 95% for electrochemical CO
2
reduction to CO. The proof-of-concept system provides a unique technological pathway for CO
2
capture and conversion from oceanwater with only electrochemical processes.
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