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Highly efficient one-pot synthesis of hexakis(m-phenyleneimine) macrocycle Cm6 from acetalprotected AB-type monomer, m-aminobenzaldehyde diethylacetal, was successfully achieved based on imine dynamic covalent chemistry and precipitation-driven cyclization. The structure of Cm6 in the solid state was determined using CP/MAS NMR, X-ray single crystallographic analysis, and WAXD. Macrocycle Cm6 is composed of six phenylene and imine bonds facing the same direction, with nitrogen atoms arranged on the outside of the ring, and has a chair conformation, as predicted from DFT calculation. The macrocycle forms π-stacked columnar aggregates and hexagonally closest-packed structure. The cyclization process was investigated using MALDI-TOF MS and NMR. A mechanism of precipitation-driven cyclization based on imine dynamic covalent chemistry and π-stacked columnar aggregation is proposed. Both the nature of imine linkage and the shape anisotropy of the macrocycle played an important role in the single one-pot synthesis. The water-mediated mutual conversion between macrocycle Cm6 and linear oligomers driven by thermal stimulation was analyzed using MALDI-TOF MS and GPC methods. Macrocycle Cm6 with a dynamic covalent imine bond exhibited self-healing properties when stimulated using heat.

The recent progress of research on polymer reactions utilizing dynamic covalent exchanges of alkoxyamine units—adducts of styryl and stable nitroxide radicals—is reviewed. The alkoxyamine derivatives derived from 2,2,6,6-tetramethylpiperidine-1-oxy (TEMPO, a stable free radical) are frequently utilized as unimolecular initiators for the nitroxide-mediated radical polymerizations. In the absence of monomers, however, the alkoxyamine derivatives can undergo intermolecular crossover reactions via a radical process upon heating. The central C–ON bonds in the alkoxyamine derivatives reversibly cleave and reform upon heating, and a mixture of alkoxyamine derivatives is able to equilibrate thermally, meaning that the covalent bonds in the alkoxyamine derivatives are considered as ‘dynamic covalent bonds.’ Unlike conventional polymers, the structures and constitutions of polymers with dynamic covalent bonds, dynamic covalent polymers, can be reorganized under appropriate conditions even after polymerization. In the present review, various types of macromolecular design, polymer reactions based on dynamic covalent exchanges of alkoxyamine units and their related research are described. Various examples of polymer reactions of main-chain-type, side-chain-type, crosslinked and star-shaped poly(alkoxyamine)s are systematically shown. Furthermore, the progress of the polymer reactions can be confirmed by diverse characterization techniques, such as spectroscopic, chromatographic, microscopic and scattering methods. The recent progress of research on polymer reactions utilizing dynamic covalent exchanges of alkoxyamine units—adducts of styryl and stable nitroxide radicals—is reviewed. Various types of macromolecular design, polymer reactions based on dynamic covalent exchanges of alkoxyamine units and their related research are described. Various examples of polymer reactions of main-chain-type, side-chain-type, crosslinked and star-shaped poly(alkoxyamine)s are systematically shown. The progress of the polymer reactions can be confirmed by diverse characterization techniques, such as spectroscopic, chromatographic, microscopic and scattering methods.

Transparent wood (TW) with excellent optical and thermal management performance has been recently developed as a promising energy-efficient building material. Here, editable shape-memory TW (ESMTW) is developed through in situ polymerization of epoxy-based dynamic covalent polymers (EDCP) into a delignified wood scaffold. ESMTW possesses stiffness at low temperature and flexibility at high temperatures, while it exhibits excellent solid-state plasticity and shape-manipulation capability under thermal stimuli. Meanwhile, ESMTW shows unique light guiding and directional scattering effects, and the transmitted light intensity distribution is tunable owing to the shape-management capability. Additionally, the resultant TW possesses great thermal insulation properties. The combination of characteristics enables TW to exhibit great promise as an advanced functional and intelligent building material toward a sustainable society, especially for three-dimensional applications ( e.g. , curved or irregularly shaped glass, windows, ceilings, rooftops.). It may also provide new ideas for fabricating transparent and shape-editable optical/electronic devices. Graphical abstract

Dynamic covalent polymers (DCPs) offer opportunities as adaptive materials of particular interest for targeting, sensing and delivery of biological molecules. In this view, combining cationic units and fluorescent units along DCP chains is attractive for achieving optical probes for the recognition and delivery of nucleic acids. Here, we report on the design of acylhydrazone-based DCPs combining cationic arginine units with π-conjugated fluorescent moieties based on thiophene-ethynyl-fluorene cores. Two types of fluorescent building blocks bearing neutral or cationic side groups on the fluorene moiety are considered in order to assess the role of the number of cationic units on complexation with DNA. The (chir)optical properties of the building blocks, the DCPs, and their complexes with several types of DNA are explored, providing details on the formation of supramolecular complexes and on their stability in aqueous solutions. The DNA-templated formation of DCPs is demonstrated, which provides new perspectives on the assembly of fluorescent DCP based on the nucleic acid structure.

The design of high-efficiency CO2 adsorbents with low cost, high capacity, and easy desorption is of high significance for reducing carbon emissions, which yet remains a great challenge. This work proposes a facile construction strategy of amino-functional dynamic covalent materials for effective CO2 capture from flue gas. Upon the dynamic imine assembly of N-site rich motif and aldehyde-based spacers, nanospheres and hollow nanotubes with spongy pores were constructed spontaneously at room temperature. A commercial amino-functional molecule tetraethylenepentamine could be facilely introduced into the dynamic covalent materials by virtue of the dynamic nature of imine assembly, thus inducing a high CO2 capacity (1.27 mmol·g−1) from simulated flue gas at 75 °C. This dynamic imine assembly strategy endowed the dynamic covalent materials with facile preparation, low cost, excellent CO2 capacity, and outstanding cyclic stability, providing a mild and controllable approach for the development of competitive CO2 adsorbents.

Dynamic covalent polymers (DCPs) that strike a balance between high performance and rapid reconfiguration have been a challenging task. For this purpose, a solution is proposed in the form of a new dynamic covalent supramolecular motif—guanidine urea structure (GUAs). GUAs contain complex and diverse chemical structures as well as unique bonding characteristics, allowing guanidine urea supramolecular polymers to demonstrate advanced physical properties. Noncovalent interaction aggregates (NIAs) have been confirmed to form in GUA‐DCPs through multistage H‐bonding and π‐π stacking, resulting in an extremely high Young's modulus of 14 GPa, suggesting remarkable mechanical strength. Additionally, guanamine urea linkages in GUAs, a new type of dynamic covalent bond, provide resins with excellent malleability and reprocessability. Guanamine urea metathesis is validated using small molecule model compounds, and the temperature dependent infrared and rheological behavior of GUA‐DCPs following the dissociative exchange mechanism. Moreover, the inherent photodynamic antibacterial properties are extensively verified by antibacterial experiments. Even after undergoing three reprocessing cycles, the antibacterial rate of GUA‐DCPs remains above 99% after 24 h, highlighting their long‐lasting antibacterial effectiveness. GUA‐DCPs with dynamic nature, tuneable composition, and unique combination of properties make them promising candidates for various technological advancements. A new dynamic covalent supramolecular motif, guanidine urea structure, is proposed and exploited to prepare thermosetting materials with reprocessability, ultrahigh modulus, and intrinsic photodynamic antibacterial characteristics. Dynamic exchange reaction of guanamine urea bonds follows the dissociative exchange mechanism. The material's ultrahigh modulus and photodynamic antibacterial characteristics are attributed to noncovalent interaction aggregates caused by multilevel H‐bonding and π‐π stacking.

Plastic recycling is a critical step toward improving waste management and achieving economic recycling. Here, a thermoset crosslinked by guanythiourea structure (GTUH network) is reported, that addresses the recycling issue of thermosets by serial hybridization of thiourea and guanidine urea. The dual dissociative dynamic exchange reaction of guanamine urea and thiourea, combined with non‐covalent hydrogen bonding interactions, endows the network with rapid relaxation ability. GTUH networks, in particular, can be recycled through continuous extrusion processing due to multiple reversible mechanisms, as opposed to hot pressing alone. Even if reprocessed by hot pressing, only 5 min at 140 °C and 10 MPa are required. The oxidation enhancement mechanism of thiourea contributes to maintaining or even improving the mechanical properties of the recycled network. Moreover, the dynamic reactions of guanythiourea structure allow for closed‐loop chemical recycling of the network. Research into recyclable carbon fiber‐reinforced composites indicates promising potential applications for this material in the circular economy and resources. A novel dynamic polyurea network based on guanythiourea structure is developed, leveraging thiourea and guanidine urea in serial hybridization to achieve rapid relaxation. Various recycling methods are investigated, including compression, welding, extrusion, and chemical recycling. Furthermore, research into recyclable carbon fiber‐reinforced composites indicates promising potential applications for this material in the circular economy and resources.

Hexakis(2-alkoxy-1,5-phenyleneimine) macrocycles were synthesized using a simple one-pot procedure through precipitation-driven cyclization. The acetal-protected AB–type monomers, 2-alkoxy-5-aminobenzaldehyde diethyl acetals, underwent polycondensation in water or acid-containing tetrahydrofuran. The precipitation–driven cyclization, based on imine dynamic covalent chemistry and π–stacked columnar aggregation, played a decisive role in the one–pot synthesis. The progress of the reaction was analyzed using MALDI–TOF mass spectrometry. The macrocycles with alkoxy chains were soluble in specific organic solvents, such as chloroform, allowing their structures to be analyzed using NMR. The shape-anisotropic, nearly planar, and shape-persistent macrocycles aggregated into columnar assemblies in polymerization solvents, driven by aromatic π-stacking. The octyloxylated macrocycle OcO–Cm6 exhibited an enantiotropic columnar liquid crystal-like mesophase between 165 °C and 197 °C. In the SEM image of (S)-(–)-3,7-dimethyloctyloxylated macrocycle (–)BCO–Cm6, columnar substances with a diameter of 200–300 nm were observed. The polymerization solution for the 2-(2-methoxyethoxy)ethoxy)ethoxylated macrocycle (TEGO–Cm6) gelled, and showed thixotropic properties by forming a hydrogen bond network.

A new strategy for nanocrystal encapsulation, release and application based on pH-sensitive covalent dynamic hyperbranched polymers is described. The covalent dynamic hyperbranched polymers, with multi-arm hydrophobic chains and a hydrophilic hyperbranched poly(amidoamine) (HPAMAM) core connected with pH-sensitive imine bonds (HPAMAM–DA), could encapsulate CdTe quantum dots (QDs) and Au nanoparticles (NPs). Benefiting from its pH response property, CdTe QDs and Au NPs encapsulated by HPAMAM–DA could be released to aqueous phase after imine hydrolysis. The released CdTe/HPAMAM and Au/HPAMAM nanocomposites exhibited excellent biological imaging behavior and high catalytic activities on p-nitrophenol hydrogenation, respectively.