Dynamic Covalent Polymer Networks: A Molecular Platform for Designing Functions beyond Chemical Recycling and Self-Healing

Diels–Alder Cycloadditions of Bio-Derived Furans with Maleimides as a Sustainable «Click» Approach towards Molecular, Macromolecular and Hybrid Systems

This mini-review highlights the recent research trends in designing organic or organic-inorganic hybrid molecular, biomolecular and macromolecular systems employing intermolecular Diels–Alder cycloadditions of biobased, furan-containing substrates and maleimide dienophiles. The furan/maleimide Diels–Alder reaction is a well-known process that may proceed with high efficiency under non-catalytic and solvent-free conditions. Due to the simplicity, 100% atom economy and biobased nature of many furanic substrates, this type of [4+2]-cycloaddition may be recognized as a sustainable “click” approach with high potential for application in many fields, such as fine organic synthesis, bioorganic chemistry, material sciences and smart polymers development.

Catalyst Control of Nanoscale Characteristic Length of the Glass Transition in Organic Strong Glass-Formers

We report the nanoscale characteristic length (ξ_α) in organic strong glass-formers at glass transition. Catalyst-dependent ξ_α of the epoxy-based covalent adaptable networks (CANs) is observed, that is, the more efficient the catalyst for the cross-linking reactions, the larger the ξ_α is, and upon thermal heating, the more broad the glass transition will be. The observed structural properties at glass transition can be correlated with the topology freezing transition where the fluctuations of network topology aroused from the bond exchange reactions are frozen. This study proposes the catalyst-dependent structural properties in CANs and may fill the structural gap between the glass transition and topology freezing transition of organic strong glass-formers.

Mechanically Interlocked Vitrimers

Mechanically interlocked networks (MINs) have emerged as an encouraging platform for the development of mechanically robust yet adaptive materials. However, the difficulty in reversibly breaking the mechanical bonds poses a real challenge to MINs as customizable and sustainable materials. Herein, we couple the vitrimer chemistry with mechanically interlocked structures to generate a new class of MINs─referred to as mechanically interlocked vitrimers (MIVs)─to address the challenge. Specifically, we have prepared the acetoacetate-decorated [2]rotaxane that undergoes catalyst-free condensation reaction with two commercially available multiamine monomers to furnish MIVs. Compared with the control whose wheels are nonslidable under applied force, our MIVs with slidable mechanically interlocked motifs showcase enhanced mechanical performance including Young's modulus (18.5 ± 0.9 vs 1.0 ± 0.1 MPa), toughness (3.7 ± 0.1 vs 0.9 ± 0.1 MJ/m³), and damping capacity (98% vs 72%). The structural basis behind unique property profiles is demonstrated to be the force-induced host-guest dissociation and consequential intramolecular sliding of the wheels along the axles. The peculiar behaviors represent a consecutive energy dissipation mechanism, which provides a complement to other pathways that mainly depend on the breaking of sacrificial bonds. Moreover, by virtue of the vitrimer chemistry of vinylogous urethanes, we impart reprocessability and chemical recyclability to the MINs, thereby empowering the reconfiguration of the networks without breaking of the mechanical bonds. Finally, it is disclosed that the intramolecular motions of [2]rotaxanes could accelerate the dynamic exchange of the vinylogous urethane bonds via loosening the network, suggestive of a synergistic effect between the dual dynamic entities.

Hierarchical Self-Assembly and Multidynamic Responsiveness of Fluorescent Dynamic Covalent Networks Forming Organogels

Smart stimuli-responsive fluorescent materials are of interest in the context of sensing and imaging applications. In this project, we elaborated multidynamic fluorescent materials made of a tetraphenylethene fluorophore displaying aggregation-induced emission and short cysteine-rich C-hydrazide peptides. Specifically, we show that a hierarchical dynamic covalent self-assembly process, combining disulfide and acyl-hydrazone bond formation operating simultaneously in a one-pot reaction, yields cage compounds at low concentration (2 mM), while soluble fluorescent dynamic covalent networks and even chemically cross-linked fluorescent organogels are formed at higher concentrations. The number of cysteine residues in the peptide sequence impacts directly the mechanical properties of the resulting organogels, Young's moduli varying 2500-fold across the series. These materials underpinned by a nanofibrillar network display multidynamic responsiveness following concentration changes, chemical triggers, as well as light irradiation, all of which enable their controlled degradation with concomitant changes in spectroscopic outputs─self-assembly enhances fluorescence emission by ca. 100-fold and disassembly quenches fluorescence emission.

Light-Induced Formation/Scission of C-N, C-O, and C-S Bonds Enables Switchable Stability/Degradability in Covalent Systems

The manipulation of covalent bonds could be directed toward degradable, recyclable, and sustainable materials. However, there is an intrinsic conflict between properties of stability and degradability. Here we report light-controlled formation/scission of three types of covalent bonds (C-N, C-O, and C-S) through photoswitching between equilibrium and nonequilibrium states of dynamic covalent systems, achieving dual benefits of photoaddressable stability and cleavability. The photocyclization of dithienylethene fused aldehyde ring-chain tautomers turns on the reactivity, incorporating/releasing amines, alcohols, and thiols reversibly with high efficiency, respectively. Upon photocycloreversion the system is shifted to kinetically locked out-of-equilibrium form, enabling remarkable robustness of covalent assemblies. Reaction coupling allows remote and directional control of a diverse range of equilibria and further broadens the scope. Through locking and unlocking covalent linkages with light when needed, the utility is demonstrated with capture/release of bioactive molecules, modification of surfaces, and creation of polymers exhibiting tailored stability and degradability/recyclability. The versatile toolbox for photoswitchable dynamic covalent reactions to toggle matters on and off should be appealing to many endeavors.

Reshaping Membrane Polymorphism of Polymer Vesicles through Dynamic Gas Exchange

The quest for a universal method to shape the vesicular morphology in dynamic and diversified manners is a challenging topic of cell mimicry. Here we present a simple gas exchange strategy that can direct the deformation movements of polymer vesicles. Such vesicles are assembled by a class of gas-based dynamic polymers, where CO₂ connects between the frustrated Lewis pair via dynamic gas-bridged bonds. Use of other competitive gases (N₂O, SO₂, or C₂H₄) to in situ exchange the CO₂ linkages can change the polymer structure and drive the membrane to proceed with three fundamental movements, including membrane stretching, membrane incurvation, and membrane protrusion, thus remolding the shapes of polymersomes. The choices of gas types, concentrations, and combinations are crucial to adjusting the vesicle evolution, local change of membrane curvature, and anisotropic geometrical transformation. This will become a generalized strategy to control the vesicular polymorphism and deformable behavior.

A Photoinduced Dual-Wavelength Approach for 3D Printing and Self-Healing of Thermosetting Materials

Vat photopolymerization-based 3D printing techniques have been widely used to produce high-resolution 3D thermosetting materials. However, the lack of repairability of these thermosets leads to the production of waste. In this study, reversible addition fragmentation chain transfer (RAFT) agents are incorporated into resin formulations to allow visible light (405 nm) mediated 3D printing of materials with self-healing capabilities. The self-healing process is based on the reactivation of RAFT agent embedded in the thermosets under UV light (365 nm), which enables reformation of the polymeric network. The self-healing process can be performed at room temperature without prior deoxygenation. The impact of the type and concentration of RAFT agents in the polymer network on the healing efficiency is explored. Resins containing RAFT agents enable 3D printing of thermosets with self-healing properties, broadening the scope of future applications for polymeric thermosets in various fields.

Acid-Resistance and Self-Repairing Supramolecular Nanoparticle Membranes via Hydrogen-Bonding for Sustainable Molecules Separation

Functional membranes generally wear out when applying in harsh conditions such as a strong acidic environment. In this work, high acid-resistance, long-lasting, and low-cost functional membranes are prepared from engineered hydrogen-bonding and pH-responsive supramolecular nanoparticle materials. As a proof of concept, the prepared membranes for dehydration of alcohols are utilized. The synthesized membranes have achieved a separation factor of 3000 when changing the feed solution pH from 7 to 1. No previous reports have demonstrated such unprecedentedly high-record separation performance (pervaporation separation index is around 1.1 × 107  g m-2  h-1 ). More importantly, the engineered smart membrane possesses fast self-repairing ability (48 h) that is inherited from the dynamic hydrogen bonds between the hydroxyl groups of polyacrylic acid and carbonyl groups of polyvinylpyrrolidone. To this end, the designed supramolecular materials offer the membrane community a new material type for preparing high acid resistance and long-lasting membranes for harsh environmental cleaning applications.

Strong, Self-Healing Gelatin Hydrogels Cross-Linked by Double Dynamic Covalent Chemistry

Hydrogels constructed from natural sources have received increased attention recently, including applications in biomedical fields. They are protein or polysaccharide cross-linked scaffolds that display water retention and are able to recognize host cargos. Their excellent biocompatibility does not always combine with high mechanical strength (up to 136 kPa) and thermostability, making them less useful in biomedical applications. This paper reports biocompatible gelatin hydrogels, double cross-linked via imine and Diels-Alder (DA) dynamic covalent frameworks. They showed integrated advantages of adjustable and durable mechanical strength, good thermal stability, biocompatibility for promoting cell growth and reasonable degradable rate. These hydrogels possess remarkable self-healing property, acid/alkali resistance at 65 °C and good integrity in organic solvents at 130 °C, holding great potential for biomedical applications in the areas such as cartilage regeneration, articular reconstruction or soft robotics.

Catalysis in Single Crystalline Materials: From Discrete Molecules to Metal-Organic Frameworks

Catalysis is one of the key techniques for people's modern life. It has created numerous essential chemicals such as biomedicines, agricultural chemicals and unique materials. Heterogeneous catalysis is the new emerging method with reusable catalysts. Among heterogenous catalysis patterns developed so far, single crystalline catalysis has become the promising one owing to its high catalytic density and selectivity resulted by the inherent porosity, orderliness of the lattices and permeability. These crystalline catalysts could be used in various reactions such as photo-dimerization, Diels-Alder reaction, CO₂ transformation and so on. In this review, we highlighted the reported works about the single crystalline catalysts. Both discrete small molecules and metal-organic frameworks (MOFs) have been used to prepare single crystals for catalysis. For discrete molecules based crystalline catalysts, coordinated and covalent molecules have been used. There were more catalytic modes in crystalline MOF catalysts. Three patterns were identified in this review: single crystalline MOFs i) without catalytic sites, ii) with inherent catalytic features and iii) with introducing catalytic units by post synthetic modification. Based on these examples, this review committed to provide the inspirations for the further design and application of single crystalline materials.

Unlocking Chemically Encrypted Information Using Three Types of External Stimuli

Encryption is critical to information security; however, existing chemical-based information encryption strategies are still in their infancy. We report here a new approach to chemical encryption involving a supramolecular gel QR (quick response) code with multiple encryption functions. Three color "turn-on" supramolecular polymer gels, G1-G3, were prepared that produce pink, purple, and yellow colors when subject to treatment with acetic acid vapor, UV light, and methanolic FeCl₃, respectively. As the result of hydrogen-bonding interactions at the gel interfaces, the three gels can be assembled to produce gel G4. Engraving a QR code pattern onto G4 then gave gel G5. When one or two stimuli are applied to the individual pieces corresponding to the QR engraved versions of the gels G1-G3 making up G5, a complete scannable pattern is not displayed, and the stored information cannot be recognized. Only when three different stimuli are applied at the same time does G5 give a complete recognizable pattern allowing the stored information to be retrieved. This strategy was applied to the decryption-based opening of a coded lock.

Preparation of Poly(thiol-urethane) Covalent Adaptable Networks Based on Multiple-Types Dynamic Motifs

To solve the issue of polymeric materials recycling, developing intrinsic self-healing materials containing dynamic bonds has attracted many researchers' highly concerning. However, the tradeoff between their mechanical strength and stretchability always does not avoid. Herein, to surmount the above tradeoff, metal-ligand (Cu²⁺ -S) interactions are introduced into the cross-linking polythiourethane covalent adaptable networks (PTU CANs) with three kinds of dynamic motifs (thiourethane, disulfide, and hydrogen bonds). When the molar ratio of Cu²⁺ to S is 6.37%, the break strength (9.41 ± 0.34 MPa) and Young's modulus (26.02 ± 0.55 MPa) of the metal-ligand coordination complex PTU (Cu²⁺ -PTU-3) dramatically increase, whereas the peak strain almost does not decline (454.44 ± 3.95%). To conduct the repairing, Cu²⁺ -PTU-3 is further confirmed excellent repairing capability. Therefore, these new PTU CANs have significant potential for the new self-healing materials.

Fabricating a Repairable, Recyclable, Imine-based Dynamic Covalent Thermosetting Resin with Excellent Water Resistance by Introducing Dynamic Covalent Oxime Bonds

The sustainable production of adaptive, recyclable and imine-based dynamic covalent thermosetting resins (DCTRs) presents an opportunity for polymer scientists to address the prevalent environmental and energy concerns associated with current petroleum-based plastics. However, the imine-based DCTRs easily decompose in the presence of water, which can weaken the mechanical properties in imine-based polymers. In this study, we designed oxime-imine DCTRs that are stable in the presence of water and exhibit good mechanical properties. In the presence of one kind of amino group catalyst, the oxime-imine DCTRs could be completely recycled. Additionally, these well-designed oxime-imine DCTRs have good mechanical properties, high glass transition temperatures (166 °C), and good thermal stabilities. Taken together, this work offers a sustainable solution for the design and manufacture of high-value degradable materials intended for applications in which recyclability and reusability are indispensable.

Mechanically Strong, Autonomous Self-Healing, and Fully Recyclable Silicone Coordination Elastomers with Unique Photoluminescent Properties

The combination of excellent mechanical performances, high reprocess efficiency, and wide-range tunability for functional dynamic siloxane materials is a challenging subject. Herein, the fabrication of mechanically strong, autonomous self-healing, and fully recyclable silicone elastomers with unique photoluminescent properties by coordination of poly(dimethylsiloxane) (PDMS) containing coordination bonding motifs with Zn²⁺ ions is reported. Salicylaldimine groups, which are introduced into the polysiloxane backbone via mild Schiff-base reaction, coordinate with zinc ions to form elastomeric networks The obtained supramolecular elastomers have excellent mechanical properties, with the optimized tensile strength up to 10.0 MPa, which is unprecedented among the reported thermoplastic polysiloxane-based elastomers. Both mechanical properties and stress relaxation kinetics are tunable via adjusting the length of PDMS segments or the molar ratio of metal versus salicylaldimine. Furthermore, these elastomers can be conveniently healed and recycled to regain their original mechanical properties and integrity under mild conditions. In addition, this new kind of polysiloxane also exhibits coordination-enhanced fluorescence, showing great promise for preparing photoluminescent elastomers or coatings.

Catalyst-Free Vitrimer Cross-Linked by Biomass-Derived Compounds with Mechanical Robustness, Reprocessability, and Multishape Memory Effects

Vitrimerization of thermoset polymers plays an important role in addressing resource recovery and reuse. Vitrimer elastomers with good mechanical properties often require well-designed crosslinking agents or fillers, but this increases processing complexity or reduces vitrimer dynamic properties. In this report, a simple green strategy to build a strong vitrimer elastomer is designed. Commercially available epoxidized natural rubber (ENR) is cross-linked with biomass-derived D-Fructose 1,6-bisphosphoric acid to get a vitrimer elastomer cross-linked by β-hydroxy phosphate ester bonds and has abundant hydrogen bonds. Hydrogen bonds can preferentially break and dissipate energy under external forces, which makes the sample robust. The topological network can be reformed at high temperatures through the dynamic exchange of β-hydroxy phosphate ester bonds, which gives the material malleability and recyclability. In addition, through the strategy of combining reprocessing and welding, multiple shape memory effects can be achieved in one postprocessing step. Considering that a variety of commercially available epoxy polymers are easily available, it is believed that this strategy can be a simple and versatile way to enable commercial epoxy polymers to achieve green crosslinking through biomass crosslink agents, which results in robust and recyclable vitrimers based on β-hydroxy phosphate bonds.

Arbitrarily Reconfigurable and Thermadapt Reversible Two-Way Shape Memory Poly(thiourethane) Accomplished by Multiple Dynamic Covalent Bonds

The fabrication of a single polymer network that exhibits a good reversible two-way shape memory effect (2W-SME), can be formed into arbitrarily complex three-dimensional (3D) shapes, and is recyclable remains a challenge. Herein, we design and fabricate poly(thiourethane) (PTU) networks with an excellent thermadapt reversible 2W-SME, arbitrary reconfigurability, and good recyclability via the synergistic effects of multiple dynamic covalent bonds (i.e., ester, urethane, and thiourethane bonds). The PTU samples with good mechanical performance simultaneously demonstrate a maximum tensile stress of 29.7 ± 1.1 MPa and a high strain of 474.8 ± 7.5%. In addition, the fraction of reversible strain of the PTU with 20 wt % hard segment reaches 22.4% during the reversible 2W-SME, where the fraction of reversible strain is enhanced by self-nucleated crystallization of the PTU. A sample with arbitrarily complex permanent 3D shapes can be realized via the solid-state plasticity, and that sample also exhibits excellent reversible 2W-SME. A smart light-responsive actuator with a double control switch is fabricated using a reversible two-way shape memory PTU/MXene film. In addition, the PTU networks are de-cross-linked by alcohol solvolysis, enabling the recovery of monomers and the realization of recyclability. Therefore, the present study involving the design and fabrication of a PTU network for potential applications in intelligent actuators and multifunctional shape-shifting devices provides a new strategy for the development of thermadapt reversible two-way shape memory polymers.

Low-Voltage Actuator with Bilayer Structure for Various Biomimetic Locomotions

Composites based on a shape-memory polymer doped with conductive particles are considered as soft actuators for artificial muscles and robots. Low-voltage actuating is expected to reduce equipment requirement and safety hazards, which requires a highly conductive particle content but weakens the reversible deformation. The spatial distribution of the conductive particle is key to decreasing the actuating voltage and maintaining the reversible deformation. Herein, an approach of fabricating a low-voltage actuator that can perform various biomimetic locomotions by spraying and hot pressing is reported. Carbon nanotubes (CNTs) are enriched inside the surface layer of poly(ethylene-co-vinyl acetate) (EVA) to form a high-density conductive network without degradation of the reversible deformation. The bilayer CNT/EVA actuator exhibits a reversible transformation of more than 10% even with 100 cycles, which requires an applied voltage of just 15 V. Taking advantage of the reprogrammability of the CNT/EVA actuator and reversible shift between the different shapes, different biomimetic locomotions (sample actuator, gripper, and walking robot) are demonstrated without any additional mechanical components. A scheme combining the electrical properties and the shape-memory effect provides a versatile strategy to fabricate low-voltage-actuated polymeric actuators, providing inspiration in the development of electrical soft actuators and biomimetic devices.

Dynamic Semicrystalline Networks of Polypropylene with Thiol-Anhydride Exchangeable Crosslinks

Thermoplastic polyolefins (TPOs) crosslinked by dynamic covalent bonds (xTPOs) have the potential to be the most utilized class of polymer in the world, with applications ranging from household and automotive to biomedical devices and additive manufacturing. xTPO combines the benefits of thermoplastics and thermosets in a "single material" and potentially avoids their shortcomings. Here, we describe a new two-stage reaction extrusion strategy of TPOs with a backbone consisting of inert C-C bonds (polypropylene, PP), and thiol-anhydride, to dynamically crosslink PP through thiol-thioester bond exchange. The degree of PP crosslinking determines the rubber plateau modulus above the melting point of the plastic: the modulus at 200 °C increases from zero in the melt to 23 kPa at 6% crosslinking, to 60 kPa at 20%, to 105 kPa at 40%. The overall mechanical strength of the solid xTPO plastic is 25% higher compared to the original PP, and the gel fraction of xTPO reaches 55%. Finally, we demonstrate that the crosslinked xTPO material is readily reprocessable (recycled, remolded, rewelded, and 3D printed).

Nanostructured Ceria: Biomolecular Templates and (Bio)applications

Ceria (CeO2) nanostructures are well-known in catalysis for energy and environmental preservation and remediation. Recently, they have also been gaining momentum for biological applications in virtue of their unique redox properties that make them antioxidant or pro-oxidant, depending on the experimental conditions and ceria nanomorphology. In particular, interest has grown in the use of biotemplates to exert control over ceria morphology and reactivity. However, only a handful of reports exist on the use of specific biomolecules to template ceria nucleation and growth into defined nanostructures. This review focusses on the latest advancements in the area of biomolecular templates for ceria nanostructures and existing opportunities for their (bio)applications.

Polymers with Dynamic Bonds: Adaptive Functional Materials for a Sustainable Future

Polymeric materials play critical role in many current technologies. Among them, adaptive polymeric materials with dynamic (reversible) bonds exhibit unique properties and provide exciting opportunities for various future technologies. Dynamic bonds enable structural rearrangements in polymer networks in specific conditions. Replacement of a few covalent bonds by dynamic bonds can enhance polymeric properties, e.g., strongly improve the toughness and the adhesive properties of polymers. Moreover, they provide recyclability and enable new properties, such as self-healing and shape memory effects. We briefly overview new developments in the field of polymers with dynamic bonds and current understanding of their dynamic properties. We further highlight several examples of unique properties of polymers with dynamic bonds and provide our perspectives for them to be used in many current and future applications.

Dynamic Surfaces-Degradable Polyester Networks that Resist Protein Adsorption

We synthesized a series of novel degradable alternating copolyesters composed of diglycolic anhydride (DGA) and two epoxides, epoxymethoxytriethylene glycol (ETEG) and a photoactive crosslinking agent epoxy benzophenone (EBP). After UV crosslinking, soaking the films in a good solvent (tetrahydrofuran) removed uncrosslinked material, and the resulting film gel fractions were calculated. These network films were then degraded in buffer solutions of varying pH values. The degradation of networks with lower gel fraction (fewer crosslinks) was faster and followed first-order kinetics. In contrast, the denser network degraded slower and followed zeroth-order kinetics. The lower gel fraction networks possess a higher swelling ratio and resist bovine serum albumin (BSA) adsorption better by entropic shielding and faster degradation. In comparison, higher gel fraction networks with higher EBP mole fractions adsorb more BSA due to hydrophobic interactions and slower degradation.

The Critical Importance of Adopting Whole-of-Life Strategies for Polymers and Plastics

Plastics have been revolutionary in numerous sectors, and many of the positive attributes of modern life can be attributed to their use. However, plastics are often treated only as disposable commodities, which has led to the ever-increasing accumulation of plastic and plastic by-products in the environment as waste, and an unacceptable growth of microplastic and nanoplastic pollution. The catchphrase “plastics are everywhere”, perhaps once seen as extolling the virtues of plastics, is now seen by most as a potential or actual threat. Scientists are confronting this environmental crisis, both by developing recycling methods to deal with the legacy of plastic waste, and by highlighting the need to develop and implement effective whole-of-life strategies in the future use of plastic materials. The importance and topicality of this subject are evidenced by the dramatic increase in the use of terms such as “whole of life”, “life-cycle assessment”, “circular economy” and “sustainable polymers” in the scientific and broader literature. Effective solutions, however, are still to be forthcoming. In this review, we assess the potential for implementing whole-of-life strategies for plastics to achieve our vision of a circular economy. In this context, we consider the ways in which given plastics might be recycled into the same plastic for potential use in the same application, with minimal material loss, the lowest energy cost, and the least potential for polluting the environment.

Ionic Network Based on Dynamic Ionic Liquids for Electronic Tattoo Application

Electronic tattoos as an emerging epidermal electronic are alluring in the field of wearable electronics for their lightweight and noninvasive properties. However, the combination of flexibility, skin biocompatibility, adhesion, repairability, and erasability remains a challenge for fabricating electronic tattoos. Hence, a dynamic ionic liquid is prepared which is ideally suited for making an electronic tattoo with these challenging features at the same time. Such an intrinsically flexible electronic tattoo can be firmly attached to human skin with negligible irritation. More importantly, the existence of dynamic covalent chemistry provides the electronic tattoo with healing and erasable abilities under mild redox conditions. Owing to the high ionic conductivity of ionic liquids, the electronic tattoo exhibits excellent sensing performance in response to the temperature variation and tensile strain, which can intelligently monitor body temperature, pulse, and movement. As an extension of the application, a specially designed quadrilateral electronic tattoo can sense and distinguish multiple signals simultaneously. This concept of electronic tattoo based on the dynamic ionic liquid shows great potentials in the applications of intelligent wearable electronics.

A Mortise-and-Tenon Joint Inspired Mechanically Interlocked Network

Mortise-and-tenon joints have been widely used for thousands of years in wooden architectures in virtue of their artistic and functional performance. However, imitation of similar structural and mechanical design philosophy to construct mechanically adaptive materials at the molecular level is a challenge. Herein, we report a mortise-and-tenon joint inspired mechanically interlocked network (MIN), in which the [2]rotaxane crosslink not only mimics the joint in structure, but also reproduces its function in modifying mechanical properties of the MIN. Benefiting from the hierarchical energy dissipative ability along with the controllable intramolecular movement of the mechanically interlocked crosslink, the resultant MIN simultaneously exhibits notable mechanical adaptivity and structural stability in a single system, as manifested by decent stiffness, strength, toughness, and deformation recovery capacity.

Magnetic Dynamic Polymers for Modular Assembling and Reconfigurable Morphing Architectures

Shape-morphing magnetic soft materials, composed of magnetic particles in a soft polymer matrix, can transform shape reversibly, remotely, and rapidly, finding diverse applications in actuators, soft robotics, and biomedical devices. To achieve on-demand and sophisticated shape morphing, the manufacture of structures with complex geometry and magnetization distribution is highly desired. Here, a magnetic dynamic polymer (MDP) composite composed of hard-magnetic microparticles in a dynamic polymer network with thermally responsive reversible linkages, which permits functionalities including targeted welding for magnetic-assisted assembly, magnetization reprogramming, and permanent structural reconfiguration, is reported. These functions not only provide highly desirable structural and material programmability and reprogrammability but also enable the manufacturing of functional soft architected materials such as 3D kirigami with complex magnetization distribution. The welding of magnetic-assisted modular assembly can be further combined with magnetization reprogramming and permanent reshaping capabilities for programmable and reconfigurable architectures and morphing structures. The reported MDP are anticipated to provide a new paradigm for the design and manufacture of future multifunctional assemblies and reconfigurable morphing architectures and devices.

Shape Memory Corrosion-Resistant Polymeric Materials

Shape memory alloys, materials capable of being deformed and maintaining the deformation and additionally capable of returning to the initial position, are valued for a range of applications from actuators to flexible microdevices. Maintaining the properties that make them useful, their ability to deform and reform, requires that shape memory alloys must be protected against corrosion, in which the integration of shape memory polymers can act as a means of protection. Thus, this review is to highlight the utility of self-healing shape memory polymers as a means of corrosion inhibition. Therefore, this review discusses the benefits of utilizing self-healing shape memory polymers for the protection of shape memory, several types of self-healing polymers that could be used, means of improving or tailoring the polymers towards specific usages, and future prospects in designing a shape memory polymer for use in corrosion inhibition.

Dissociate transfer exchange of tandem dynamic bonds endows covalent adaptable networks with fast reprocessability and high performance

A covalent adaptable network combining continuous reprocessability and high performance was achieved via dissociate transfer exchange (DTE) of tandem dynamic bonds.

Catalyst-free room-temperature self-healing polymer networks based on dynamic covalent quinone methide-secondary amine chemistry

A novel type of dynamic covalent polymer network with a catalyst-free room-temperature self-healing ability was developed on a new dynamic covalent chemistry of aza-Michael addition between para-quinone methide and secondary amine.