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The emergence of covalent adaptable networks (CANs) based on dynamic covalent bonds (DCBs) presents a promising avenue for achieving resource recovery and utilization. In this study, we discovered a dynamic covalent bond called selenacetal, which is obtained through a double click reaction between selenol and activated alkynes. Density functional theory (DFT) calculations demonstrated that the ΔG for the formation of selenoacetals ranges from 12 to 18 kJ mol−1, suggesting its potential for dynamic reversibility. Dynamic exchange experiments involving small molecules and polymers provide substantial evidence supporting the dynamic exchange properties of selenoacetals. By utilizing this highly efficient click reaction, we successfully synthesized dynamic materials based on selenoacetal with remarkable reprocessing capabilities without any catalysts. These materials exhibit chemical recycling under alkaline conditions, wherein selenoacetal (SA) can decompose into active enone selenide (ES) and diselenides. Reintroducing selenol initiates a renewed reaction with the enone selenide, facilitating material recycling and yielding a newly developed dynamic material exhibiting both photo‐ and thermal responsiveness. The results underscore the potential of selenoacetal polymers in terms of recyclability and selective degradation, making them a valuable addition to conventional covalent adaptable networks. [ABSTRACT FROM AUTHOR]

Fabrication of versatile hydrogels in a facile and effective manner represents a pivotal challenge in the field of biomaterials. Herein, a novel strategy is presented for preparing on‐demand degradable hydrogels with multilevel responsiveness. By employing selenol‐dichlorotetrazine nucleophilic aromatic substitution (SNAr) to synthesize hydrogels under mild conditions in a buffer solution, the necessity of additives or posttreatments can be obviated. The nucleophilic and redox reactions between selenol and tetrazine culminate in the formation of three degradable chemical bonds—diselenide, aryl selenide, and dearomatized selenide—in a single, expeditious step. The resultant hydrogel manifests exceptional adaptability to intricate environments in conjunction with self‐healing and on‐demand degradation properties. Furthermore, the resulting material demonstrated light‐triggered antibacterial activity. Animal studies further underscore the potential of integrating metformin into Se‐Tz hydrogels under green light irradiation, as it effectively stimulates angiogenesis and collagen deposition, thereby fostering efficient wound healing. In comparison to previously documented hydrogels, Se‐Tz hydrogels exhibit controlled degradation and drug release, outstanding antibacterial activity, mechanical robustness, and bioactivity, all without the need for costly and intricate preparation procedures. These findings underscore Se‐Tz hydrogels as a safe and effective therapeutic option for diabetic wound dressings. [ABSTRACT FROM AUTHOR]

Stimulus-responsive materials containing selenide under oxidizing conditions have wide application prospects, especially in biomedicine. Due to the intricate preparation process, the scarcity of studies on the structure–activity relationship of regulatory factors in the oxidative stimulus response poses challenges to material design. Herein, based on selenol-ene chemistry, a diverse library of unsymmetric selenides is synthesized, enabling systematic investigation into the regulation of selenide oxidative elimination with variable substituent groups and positions. The α/β-positions of β-carbonyl unsymmetric selenides are efficiently modified with electron-donating or electron-withdrawing groups through a one-pot, two-step reaction involving ammonolysis of γ-selenobutyrolactone (SBL), followed by nucleophilic addition with unsaturated acrylate. In situ NMR tracking shows that the oxidative elimination of selenide had a distinct substituent effect. Both the electron and steric effects of the substituent influence the induction period of the selenide oxidative and elimination reactions. With the optimal substituent and position, the selenides would exhibit a timebomb-type response upon oxidation stimulus. Finally, a novel amphiphilic polymer comprising selenide-linked polyethylene glycol (PEG) and cholesterol moieties is synthesized as a representative ROS-sensitive material and exhibits a time-dependent reduction in micelle size. [ABSTRACT FROM AUTHOR]

Photoinduced 3D printing based on the reversible addition‐fragmentation chain transfer (RAFT) process has emerged as a robust method for creating diverse functional materials. However, achieving precise control over the mechanical properties of these printed objects remains a critical challenge for practical application. Here, we demonstrated a RAFT step‐growth polymerization of a bifunctional xanthate and bifunctional vinyl acetate. Additionally, we demonstrated photoinduced 3D printing through RAFT step‐growth polymerization with a tetrafunctional xanthate and a bifunctional vinyl acetate. By adjusting the molar ratio of the components in the printing resins, we finely tuned the polymerization mechanism from step‐growth to chain‐growth. This adjustment resulted in a remarkable range of tunable Young's moduli, ranging from 7.6 MPa to 997.1 MPa. Moreover, post‐functionalization and polymer welding of the printed objects with varying mechanical properties opens up a promising way to produce tailor‐made materials with specific and tunable properties. [ABSTRACT FROM AUTHOR]

Covalent adaptable networks (CANs) possess unique properties as a result of their internal dynamic bonds, such as self‐healing and reprocessing abilities. In this study, we report a thermally responsive C−Se dynamic covalent chemistry (DCC) that relies on the transalkylation exchange between selenonium salts and selenides, which undergo a fast transalkylation reaction in the absence of any catalyst. Additionally, we demonstrate the presence of a dissociative mechanism in the absence of selenide groups. After incorporation of this DCC into selenide‐containing polymer materials, it was observed that the cross‐linked networks display varying dynamic exchange rates when using different alkylation reagents, suggesting that the reprocessing capacity of selenide‐containing materials can be regulated. Also, by incorporating selenonium salts into polymer materials, we observed that the materials exhibited good healing ability at elevated temperatures as well as excellent solvent resistance at ambient temperature. This novel dynamic covalent chemistry thus provides a straightforward method for the healing and reprocessing of selenide‐containing materials. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: Polymer dispersity (Đ) or molecular weight distribution (MWD) is a basic but vital parameter for the properties of polymeric materials. Developing new methodologies for controlling polymer MWD is emerging as a research hotspot. However, the methods to tune polymer MWD in cationic polymerization are still not well explored. Herein, we present a simple method to control the dispersity of poly(isobutyl vinyl ether) (PIBVE) by mixing two different chain transfer agents in batch visible light induced cationic RAFT polymerization. A broad dispersity range (Đ ≈ 1.16—1.80) was successfully achieved while maintaining monomodal MWD. Moreover, chain extension of PIBVE through both cationic polymerization and radical polymerization has been studied, which also provides a method to tune polymer MWD in mechanism transformation polymerization. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: The application of reversible degenerative radical polymerization (RDRP) in the construction of polymer networks (PNs) provides a facile and convenient way to fabricate 3D objects with the ability to be posttransformed. However, the polymerization mechanism mainly relies on chain‐growth polymerization, which limits its wide application for various polymeric materials with different functionalities. Here, we present a method toward PNs by utilizing a photoinduced RAFT step‐growth polymerization, which is based on a RAFT single unit monomer insertion (SUMI) reaction between a xanthate and an alkyl vinyl group. Benefiting from this reaction, a pendant RAFT agent can be generated in each repeat unit of the backbone during the polymerization. These reactivatable dormant species can be further used for the postfunctionalization of PNs prepared by step‐growth polymerization of multifunctional monomers. Moreover, the prepared PNs are degradable owing to the introduction of ester groups, providing an avenue toward degradable and stimuli‐responsive materials. [ABSTRACT FROM AUTHOR]

Light‐regulated polymerization has emerged as a powerful tool to control the process of polymerization. However, tuning the polymer molecular weight distribution (MWD) by light is still not well developed. Here, we present a convenient approach for controlling the MWD in reversible addition‐fragmentation chain transfer (RAFT) polymerization by exploiting an ultraviolet light‐induced RAFT‐hetero‐Diels–Alder (RAFT‐HDA) reaction with a photoenol diene. The key point in this strategy is to terminate part of the propagating chains at a specific time by the RAFT‐HDA reaction. In addition, a photoenol diene with a hydroxyl group is also synthesized and successfully applied to realize this strategy, which can be further utilized for chain extension of ɛ‐caprolactone (ɛ‐CL) by ring opening polymerization to prepare diblock copolymers with different MWDs. [ABSTRACT FROM AUTHOR]

Selenium‐containing polymers have attracted considerable attention due to their unique redox responsiveness. Here, phenyl vinyl selenide (PVSe), as a functional selenium‐containing monomer, is polymerized with maleimide (MI) or its derivatives by reversible addition–fragmentation chain transfer polymerization. The resulting polymers are characterized by matrix‐assisted laser desorption/ionization time‐of‐flight mass spectroscopy and proton nuclear magnetic resonance spectra, which particularly prove the obtaining of alternating polymers through the polymerization of PVSe and MI or its derivatives. Properties of the resulting polymers are systematically investigated, such as glass transition temperature, thermal performance, and refractive indices. What's more, based on phenylseleno oxidation elimination, the alternating polymers are oxidized through 30% H2O2 to form precisely structured olefin copolymers with carboncarbon (CC) double bonds. The selective generation of double bonds in the alternating polymers is systematically studied. The efficiency of such oxidation is very high under mild conditions due to low electronegativity and bond energy of carbonselenium (CSe) bond, which provides a novel method to prepare precisely structured olefin copolymers with MI or its derivatives. [ABSTRACT FROM AUTHOR]

Selenium‐containing monomer (p‐phenylseleno) styrene (p‐PhSeSt) is polymerized by reversible addition‐fragmentation chain transfer polymerization. Polymer, (P(p‐PhSeSt)), with controlled molecular weight and narrow molecular weight is obtained. The selenide moiety in obtained P(p‐PhSeSt) can be selectively oxidized to selenoxide or selenone groups by H2O2 or NaClO, respectively. These oxidized groups can be further reduced to selenide by Na2S2O4. The structure changing of polymers during such redox cycle is characterized by nuclear magnetic resonance, X‐ray photoelectron spectroscopy, and size exclusion chromatography. Properties, such as thermal performance, glass transition temperature, water contact angles, and refractive indices, of the resulting polymers are systematically investigated before and after oxidation. In addition, SiO2 inverse opal photonic crystal (IOPC) is fabricated by sacrificial polymer colloidal template method. Owing to changes of the RIs of P(p‐PhSeSt) after selective oxidation, the predictable change of PC bandgap as a redox‐responsive PC sensor is successfully realized, which provides new perspectives for modulating photonic crystals. [ABSTRACT FROM AUTHOR]

Polymer molecular weight distribution (MWD) is a key parameter of polymers. Here we present a robust method for controlling polymer MWD in controlled cationic polymerizations. A latent mediator strategy was designed and combined with temporal programming to regenerate mediators at different times during polymerization. Both the breadths and shapes of MWD curves were tuned easily by adjusting an external light source. Bimodal, trimodal, and tetramodal distributions were obtained, and the breadths could be varied from 1.06 to 2.09. Polymers with different MWDs prepared by this method had good chain end fidelity, which was demonstrated with successful chain‐extension experiments. In addition, the introduction of temporal programming with a computer‐controlled single chip for the light source opened an avenue for the use of artificial intelligence in polymer synthesis. [ABSTRACT FROM AUTHOR]

Pendant selenium‐containing maleimide polymers with different selenium contents are synthesized via a radical copolymerization of styrene and N‐butylmaleimide phenyl selenide. The polymer structures are characterized by nuclear magnetic resonance, gel permeation chromatography, Fourier transform infrared spectroscopy, ultraviolet–visible spectroscopy, and scanning electron microscopy with an energy‐dispersive spectrometer, which results in the desired structures and selenium contents. The refractive indices of the polymers, which change as a function of different contents of selenium and oxidative stimuli by H2O2 or O3, are investigated. Finally, a photonic crystal (PC) is prepared based on the selenium‐containing polymer. The visible color changes of the PC are investigated as a function of different concentrations and contact times of O3. [ABSTRACT FROM AUTHOR]