Metal-Free Multicomponent Tandem Polymerizations of Alkynes, Amines, and Formaldehyde toward Structure- and Sequence-Controlled Luminescent Polyheterocycles

Highlighting multicomponent reactions as an efficient and facile alternative route in the chemical synthesis of organic-based molecules: a tremendous growth in the past 5 years

Since Strecker's discovery of multicomponent reactions (MCRs) in 1850, the strategy of applying an MCR approach has been in use for over a century. Due to their ability to quickly develop molecular diversity and structural complexity of interest, MCRs are considered an efficient approach in organic synthesis. Although MCRs such as the Ugi, Passerini, Biginelli, and Hantzsch reactions are widely studied, this review emphasizes the significance of selective MCRs to elegantly produce organic compounds of potential use in medicinal chemistry and industrial and material science applications, as well as the use of the MCR approach to sustainable methods. During synthesis, MCRs provide advantages such as atom economy, recyclable catalysts, moderate conditions, preventing waste, and avoiding solvent use. MCRs also reduce the number of sequential multiple reactions to one step.

Ferrocene-Based Antioxidant Self-Healing Hydrogel via the Biginelli Reaction for Wound Healing

The development of antioxidant wound dressings to remove excessive free radicals around wounds is essential for wound healing. In this study, we developed an efficient strategy to prepare antioxidant self-healing hydrogels as wound dressings by combining multicomponent reactions (MCRs) and postpolymerization modification. A polymer containing ferrocene and phenylboronic acid groups was developed via the Biginelli reaction, followed by efficient modification. This polymer is antioxidant due to its ferrocene moieties and can rapidly cross-link poly(vinyl alcohol) to realize an antioxidant self-healing hydrogel through dynamic borate ester linkages. This hydrogel has low cytotoxicity and is biocompatible. In in vivo experiments, this hydrogel is superior to existing clinical dressings in promoting wound healing. This study demonstrates the value of the Biginelli reaction in exploring biomaterials, potentially offering insights into the design of other multifunctional polymers and related materials using different MCRs.

Efficient Conversion of Inert Nitriles to Multifunctional Poly(5-amino-1,2,3-triazole)s via Regioselective Click Polymerization with Azide Monomers under Ambient Conditions

Nitrile compounds are abundant, stable, cheap, and readily available natural and chemical industrial sources. However, the efficient conversion of nitrile monomers to functional polymers is mostly limited due to their inert reactivity, and developing efficient polymerizations based on nitrile monomers under very mild conditions is still a big challenge. In this work, a facile and powerful base-catalyzed acetonitrile-azide click polymerization was successfully established under ambient conditions. This polymerization also enjoys the merits of short reaction time (15 min), 100% atom economy, transition-metal-free catalyst system, and regioselectivity. A series of poly(5-amino-1,2,3-triazole)s (PATAs) with high weight-average molecular weights (Mw, up to 204,000) were produced in excellent yields (up to 99%). The PATAs containing tetraphenylethene (TPE) moieties exhibit unique aggregation-induced emission (AIE) characteristics, which could be used to sensitively detect Fe(III) ions with a low limit of detection (1.205 × 10-7 M) and to specifically image lysosomes of living cells. Notably, PATAs could be facilely post-modified due to their containing primary amino groups in the polymer chains even through a one-pot tandem reaction. Thus, this work not only establishes a new powerful click polymerization to convert stable nitriles but also generates a series of PATAs with versatile properties for diverse applications.

Advances in natural polysaccharides for gold recovery from e-waste: Recent developments in preparation with structural features

The increasing demand for gold because of its high market price and its wide use in the electronic industry has attracted interest in gold recovery from electronic waste (e-waste). Gold is being dumped as solid e-waste which contains gold concentrations ten times higher than gold ores. Adsorption is a widely used approach for extracting gold from e-waste due to its simplicity, low cost, high efficiency, and reusability of adsorbent material. Natural polysaccharides received increased attention due to their natural abundance, multi-functionality, biodegradability, and nontoxicity. In this review, a brief history, and advancements in this technology were evaluated with recent developments in the preparation and mechanism advancements of natural polysaccharides for efficient gold recovery. Moreover, we have discussed some bifunctional modified polysaccharides with detailed gold adsorption mechanisms. The modified adsorbent materials developed from polysaccharides coupled with inorganic/organic functional groups would demonstrate an efficient technology for the development of new bio-based materials for efficient gold recovery from e-waste. Also, future views are recommended for highlighting the direction to achieve fast and effective gold recovery from e-waste in a friendly and sustainable manner.

One-pot multicomponent polymerization towards heterocyclic polymers: a mini review

Multicomponent polymerization (MCP) is an innovative field related to polymer-based chemistry that offers numerous advantages derived from multicomponent reactions (MCRs). One of the key advantages of MCP is its ability to achieve high efficiency. Additionally, MCP offers other advantages, including operational simplicity, mild reaction conditions, and atom economy. MCP is a versatile technique that is used for synthesizing a wide range of analogs from several classes of heterocyclic compounds. The ring structures of heterocyclic polymers give them different mechanical, photophysical, and electrical properties to other types of polymers. Because of their unique properties, heterocyclic polymers have been widely utilized in various significant applications. MCRs are a type of chemical reaction that can be used to synthesize a wide variety of compounds in a single pot, which allows researchers to quickly assemble libraries of compounds. The development of MCPs from MCRs has made it easier to access a library of polymers with tunable structures. However, MCPs related to alkynes or acetylene triple bonds have more potential. In this review study, we provide an overview of the synthesis of heteroatom-functional polymers and alkyne-based development or other reactions such as Cu-catalyzed, catalyst-free, MCCP, MCTPs, green monomers, A3 coupling reactions, Passerini reactions, and sequence- and controlled-multicomponent polymerization. The up-to-date progress provides a convenient and efficient kind of approach related to heteroatoms and MCP synthesis, and perspectives in terms of future directions are also discussed in the study.

Recent progress on polymerization-induced emission

The aggregate luminescence behaviors of polymeric luminescent materials have been attracting great attention. However, the importance of the polymerization process on luminescence, namely, polymerization-induced emission (PIE), has rarely been overviewed. In this review, recent advances in polymerization with PIE effects are summarized, including PIE with aromatic rings based on one-/two-/multi-component polymerizations, and PIE without aromatic rings according to disparate mechanisms of polymerizations. Typical examples are selected to elaborate the basic design principles, as well as the properties and potential applications of the luminous polymers. Moreover, the challenges and perspectives in this area are also discussed.

Superhydrophobic Coatings Composed of Multifunctional Polymers Synthesized Using Successive Modification of Dihydropyrimidin-2(1H)-thione

Polymer synthesis via multicomponent reactions (MCRs) has opened avenues in polymer chemistry and led to the development of various types of functional polymers. Herein, we developed a strategy to prepare multifunctional polymers via the successive modification of dihydropyrimidin-2(1H)-thione (DHPMT), which can be generated by the tricomponent Biginelli reaction. Four hydrophobic polymers were efficiently prepared by using DHPMT derivatives. These polymers can be dip-coated onto the oxidized copper mesh to obtain superhydrophobic meshes because of the strong attractive forces between the DHPMT derivatives and Cu(II). The optimized mesh has self-cleaning properties and outstanding stability in various liquid environments; it has also been successfully applied for oil/water separation with high separation efficiency and good durability. These results demonstrate that successive modification of DHPMT is a promising method for fabricating multifunctional polymers, which may have applications in polymer chemistry and materials science.

Poly(vinyl alcohol) Modified via the Hantzsch Reaction for Biosafe Antioxidant Self-Healing Hydrogel

Efficient routes for the preparation of functional self-healing hydrogels from functional polymers are needed. In this study, we developed a strategy to effectively produce a vanillin-modified poly(vinyl alcohol) (PVA-vanillin) through the Hantzsch reaction. This polymer was cross-linked with a phenylboronic acid-containing polymer (PB) that was also prepared using the Hantzsch reaction to fabricate a hydrogel through borate ester linkages under mild conditions (25 °C, pH ∼ 7.4). This hydrogel had excellent antioxidant abilities due to the 1,4-dihydropyridine (DHP) rings and the vanillin moieties in the hydrogel structures; it was also self-healable and injectable owing to the dynamic borate ester linkages. Furthermore, the antioxidant self-healing hydrogel had low cytotoxicity and exhibited favorable safety in animal experiments, indicating its potential as a safe implantable cell or drug carrier. This study developed a method for preparing functional polymers and related self-healing hydrogels in a facile manner; it demonstrated the value of the Hantzsch reaction in exploiting antioxidant self-healing hydrogels for biomedical applications, which may provide insight into the design of other functional self-healing hydrogels through different multicomponent reactions.

Recent Advances and Challenges in Barbier Polymerization

The Barbier reaction, a classical name reaction for carbon-carbon bond formation, has played important roles in organic chemistry for over 120 years. The introduction of the Barbier reaction into polymer chemistry for the development of a novel Barbier polymerization, expands the methodology, monomer, chemical structure and property libraries of polymerization, aggregation-induced emission (AIE) and non-traditional intrinsic luminescence (NTIL). This mini review focuses on Barbier polymerization, including the brief introduction of the history and importance of polymerization methods design and the achievements of Barbier polymerization from molecular design strategies, functionalities and properties. An outlook of Barbier polymerization is also proposed. This mini review on Barbier polymerization therefore may cause inspirations to scientists in different fields.

A Review on The Medicinal And Industrial Applications of N-Containing Heterocycles

Nitrogen-containing heterocycles constitute an important division of organic chemistry. The structural and functional diversity in nitrogen-containing heterocyclic compounds emanates from the presence and nature of the heteroatom that optimizes the compound for a specific application. Nitrogen heterocycles have been found to mimic various endogenous metabolites and natural products, highlighting their pivotal role in current drug design. Their applications are manifold and are predominantly used as pharmaceuticals, corrosion inhibitors, polymers, agrochemicals, dyes, developers, etc. Additionally, their catalytic behavior has rendered these compounds notable precursors in synthesizing various important organic compounds. The rate at which nitrogen heterocycles are synthesized explains this organic chemistry domain's vitality and usefulness. The present review article focuses on nitrogen-containing heterocycles as a versatile scaffold for current applications of organic chemistry.

Stepping Further from Coupling Tools: Development of Functional Polymers via the Biginelli Reaction

Multicomponent reactions (MCRs) have been used to prepare polymers with appealing functions. The Biginelli reaction, one of the oldest and most famous MCRs, has sparked new scientific discoveries in polymer chemistry since 2013. Recent years have seen the Biginelli reaction stepping further from simple coupling tools; for example, the functions of the Biginelli product 3,4-dihydropyrimidin-2(1H)-(thi)ones (DHPM(T)) have been gradually exploited to develop new functional polymers. In this mini-review, we mainly summarize the recent progress of using the Biginelli reaction to identify polymers for biomedical applications. These polymers have been documented as antioxidants, anticancer agents, and bio-imaging probes. Moreover, we also provide a brief introduction to some emerging applications of the Biginelli reaction in materials and polymer science. Finally, we present our perspectives for the further development of the Biginelli reaction in polymer chemistry.

A Strategy Based on Aggregation-Induced Ratiometric Emission to Differentiate Molecular Weight of Supramolecular Polymers

Molecular weight has an important bearing on the properties of supramolecular polymers. However, the intuitive differentiation of the molecular weight of supramolecular polymers remains challenging. Given this situation, establishing a reliable relationship between fluorescence properties and molecular weight may be a promising strategy. Herein, we prepared a supramolecular monomer M1 with aggregation-induced ratiometric emission characteristics. With the increasing M1 concentration (0.100-100 mM), the average degree of polymerization (DP_DOSY ) rose from 1.00 to 293. Meanwhile, the color changed from dark blue to cyan, finally to yellow-green in the same concentration range. Hence, the intuitive relationship between DP_DOSY and fluorescence colors was constructed, allowing the visual differentiation of molecular weight. Moreover, the fluorescence color could be regulated by introducing a competitive molecule to induce the depolymerization of supramolecular polymers.

Iterative Synthesis of Stereo- and Sequence-Defined Polymers via Acid-Orthogonal Deprotection Chemistry

Absolute control over polymer stereo- and sequence structure is highly challenging in polymer chemistry. Here, an acid-orthogonal deprotection strategy is proposed for the iterative synthesis of a family of unimolecular polymers starting with enantiopure serines, featuring precise sequence, stereoconfiguration and side-chain functionalities that cannot be achieved using traditional polymerization techniques. Acid-orthogonal deprotections proceed independently of one another by the selection of protecting groups that feature the respective acid-lability. Under p-toluenesulfonic acid, acidolysis of tert-butyloxycarbonyl can proceed exclusively, while low-dosage trifluoroacetic acid and low temperature only trigger the selective and quantitative cleavage of trityl. The pioneering use of this acid-orthogonal deprotection chemistry increases the compatibility with otherwise sensitive groups and opens up pathways to facilely introduce structural and functional diversity into stereo- and sequence-defined polymers, thus imparting their unique properties beyond natural biopolymers.

Synthesis of poly-tetrahydropyrimidine antibacterial polymers and research of their basic properties

Modern medicine has increasingly higher requirements for antibacterial materials. To overcome this challenge, we use alkynyl monomers, amino monomers, formaldehyde, and acetic acid as raw materials to synthesize a series of poly-tetrahydropyrimidine (P-THP) polymers through multicomponent polymerizations (MCPs). P-THP polymers can effectively inhibit the growth of Gram-positive bacteria (Staphylococcus aureus, S. aureus) and Gram-negative bacteria (Escherichia. coli, E. coli), and can prevent bacteria from developing drug resistance within at least 16 generations. Besides, we prepared P-THP antibacterial coatings and explored their antibacterial properties. In vitro antibacterial experiments showed that P-THP coatings can prevent the formation of bacterial biofilms, and the coatings have a lasting killing effect on E. coli and S. aureus. The mouse wound infection experiments proved that P-THP polymers can significantly accelerate skin tissue regeneration and wound healing. Moreover, the P-THP textile obtained by electrospinning also has antibacterial properties and has great application prospects in the field of N95 masks. Generally speaking, P-THP polymers have considerable application potential in the field of treating bacterial infections and promoting wound healing.

Introducing the aza-Michael addition reaction between acrylate and dihydropyrimidin-2(1H)-thione into polymer chemistry

The aza-Michael addition reaction between dihydropyrimidin-2(1H)-thione and acrylate has been used to fabricate new polymers through different synthesis routes.

Room-temperature Barbier single-atom polymerization induced emission as a versatile approach for the utilization of monofunctional carboxylic acid resources

Barbier polymerization is realized at room-temperature with single-atom polymerization and polymerization-induced emission characteristics, which exhibits capability on sensitive explosive detection and artificial light-harvesting system fabrication.

Three-Component Dynamic Covalent Chemistry: From Janus Small Molecules to Functional Polymers

A new multicomponent reaction involving 2-hydroxybenzaldehyde, amine, and 2-mercaptobenzaldehyde (HAM reaction) has been developed and applied to multicomponent polymerization and controlled radical polymerization for the construction of random and block copolymers. This chemistry features mild reaction conditions, high yield, simple isolation, and water as the only byproduct. With the advantages of the distinct nucleophilicity of thiol and hydroxyl groups, the chemistry could be used for stepwise labeling and modifications on primary amines. The Janus chemical joint formed from this reaction exhibits degradability in buffers and generates the corresponding starting reagents, allowing amine release. Interestingly, the chemical joint exhibits thermally activated reversibility with water as the catalyst. This multicomponent dynamic covalent feature has been applied to the metamorphosis of random and block copolymers, generating polymers with diverse architectures. This chemistry is expected to be broadly applicable to synthetic polymer chemistry and materials science.

De Novo Design of Entropy-Driven Polymers Resistant to Bacterial Attachment via Multicomponent Reactions

Nonbactericidal polymers that prevent bacterial attachment are important for public health, environmental protection, and avoiding the generation of superbugs. Here, inspired by the physical bactericidal process of carbon nanotubes and graphene derivatives, we develop nonbactericidal polymers resistant to bacterial attachment by using multicomponent reactions (MCRs) to introduce molecular "needles" (rigid aliphatic chains) and molecular "razors" (multicomponent structures) into polymer side chains. Computer simulation reveals the occurrence of spontaneous entropy-driven interactions between the bacterial bilayers and the "needles" and "razors" in polymer structures and provides guidance for the optimization of this type of polymers for enhanced resistibility to bacterial attachment. The blending of the optimized polymer with commercially available polyurethane produces a film with remarkably superior stability of the resistance to bacterial adhesion after wear compared with that of commercial mobile phone shells made by the Sharklet technology. This proof-of-concept study explores entropy-driven polymers resistant to bacterial attachment via a combination of MCRs, computer simulation, and polymer chemistry, paving the way for the de novo design of nonbactericidal polymers to prevent bacterial contamination.

In Situ Generation of Heterocyclic Polymers by Triple-Bond Based Polymerizations

Stemming from unique ring structures, heterocyclic polymers exhibit distinguished electrical, mechanical, and photophysical properties and have been widely used in a variety of important applications. Along with the technological significance are the challenges in their synthesis. Traditional synthetic strategies toward heterocyclic polymers often require the direct attachment of heterocycles to polymer backbones, which are generally limited by the lack of suitable and low-cost heterocyclic monomers, tedious reaction process, difficulties in incorporation of multiple substitutents, etc. Alternatively, in situ construction of heterocyclic polymers via triple-bond based polymerization offers promising prospects. This review summarized the recent progress on polymerizations of triple-bond based monomers including alkynes, nitriles, and isonitriles that can in situ generate heterocyclic polymers. The properties and advanced applications of the derived heterocyclic polymers will also be discussed. Finally, the future perspectives and challenges in this field will be addressed.

Multicomponent Spiropolymerization of Diisocyanides, Diethyl Acetylenedicarboxylate, and Halogenated Quinones

Multicomponent spiropolymerization (MCSP) provides an efficient synthetic tool for the construction of spiropolymers based on nonspiro monomers. In this study, a method of MCSP using diisocyanides 1, diethyl acetylenedicarboxylate 2, and halogenated quinones 3 is developed for the in situ construction of bis-spiropolymers with high molecular weights (M_w up to 29 200) and good yields (up to 87.7%) under mild reaction conditions. The structure of the obtained bis-spiropolymers is confirmed by gel permeation chromatography, Fourier transform infrared spectroscopy, and nuclear magnetic resonance analysis. Halogenated bis-spiropolymers show good thermal stability, good solubility, and film-forming ability. The photosensitizer rhodamine B is used as a doping agent to induce the photodegradation of the polymer P1a3c into small-molecule segments, which results in the slow release of halogenated spiro-groups under irradiation with simulated sunlight. This finding reveals that P1a3c has the potential to be applied in pesticides. Therefore, this MCSP is a novel method for preparing halogen-containing bis-spiropolymers, which accelerates the development of multifunctional polymer materials.

Pillararene-based AIEgens: research progress and appealing applications

The pillararene-based AIEgens and AIE materials, constructed using different assembly forms, show attractive applications in various areas.

Facile Multicomponent Polymerization and Postpolymerization Modification via an Effective Meldrum's Acid-Based Three-Component Reaction

Providing access to highly diverse polymer structures by multicomponent reactions is highly desirable; efficient Meldrum's acid-based multicomponent reactions, however, have been rarely highlighted in polymer chemistry. Here, the three-component reaction of Meldrum's acid, indole, and aldehyde is introduced into polymer synthesis. Direct multicomponent polymerization of Meldrum's acid, dialdehyde, and diindole can perform under mild conditions, resulting in complex Meldrum's acid-containing polymers with well-defined structures, and high molecular weights. Additionally, nearly quantitative postpolymerization modification can also perform via this Meldrum's acid-based multicomponent reaction. These results indicate that Meldrum's acid-based multicomponent reaction will be a potential tool to prepare novel polymers.

Metal-Free Catalysts for the Polymerization of Alkynyl-Based Monomers

Novel polymerizations based on alkyne monomers are becoming a powerful tool to construct polymers with unique structures and advanced functions in the areas of polymer and material sciences, and scientists have been attracted to develop a variety of novel polymerizations in recent decades. Therein, catalytic systems play an indispensable role in the influence of polymerization efficiencies and the performances of the resultant polymers. Concerning the shortcomings of metallic catalysts, much of the recent research focus has been on metal-free polymerization systems. In this paper, metal-free catalysts are classified and the corresponding polymerizations are reviewed, including organobase-catalyzed polymerizations, Lewis-acid-catalyzed polymerizations, as well as catalyst-free polymerizations. Moreover, the challenges and perspectives in this area are also briefly discussed.

Catalyst-Free Four-Component Polymerization of Propiolic Acids, Benzylamines, Organoboronic Acids, and Formaldehyde toward Functional Poly(propargylamine)s

Multicomponent polymerizations (MCPs) are a group of fascinating polymer synthesis approaches that are developed rapidly in the recent decade. As a popular alkyne-based MCP, the A³ -polycouplings of alkynes, aldehydes, and amines are developed for the synthesis of poly(propargylamine)s under the catalysis of metal catalysts. In this work, through the design of carboxylic acid group-activated alkyne monomers, a catalyst-free, four-component polymerization of propiolic acids, benzylamines, organoboronic acids, and formaldehyde is reported under mild condition at 45 °C in dichloroethane. This four-component polymerization is applicable to different monomer structures, which can afford seven poly(propargylamine)s with up to 94% yields and molecular weights of up to 13 900 g mol^-1 . Moreover, the poly(propargylamine)s demonstrate good solubility and processibility, high thermal stability and light refractivity, unique photophysical property, and so on. The simple monomers, mild condition, low cost, high efficiency, and procedure simplicity of this catalyst-free four-component polymerization demonstrates an elegant example of functional polymer synthesis.

Poly-tetrahydropyrimidine Antibacterial Hydrogel with Injectability and Self-Healing Ability for Curing the Purulent Subcutaneous Infection

Infections caused by pathogenic microorganisms have always been the Achilles heel in the clinic. In this work, to overcome this conundrum, we proposed an injectable multifunctional hydrogel material with outstanding antibacterial properties and self-healing properties and no adverse effects on health. The cross-linked hydrogel with three-dimensional (3D) networks was quickly formed via the dynamic Schiff base between amino-modified poly-tetrahydropyrimidine (PTHP-NH₂) and multiple vanillin polymer P(DMA-VA) in 30 s. This hydrogel composite presents effective defense against both Gram-positive and Gram-negative bacteria, especially for the pyogenic Staphylococcus aureus. Moreover, the hydrogel showed almost no hemolysis and cytotoxicity. In vivo investigations indicated that hydrogels effectively killed S. aureus and protected against deterioration of inflammation. Besides, bioimaging of mice demonstrated that the hydrogel could be completely metabolized within 16 h. In a nutshell, given its outstanding antibacterial property and biocompatibility, the novel hydrogel could be an ideal candidate for the subcutaneous infection application.

Unusual light-driven amplification through unexpected regioselective photogeneration of five-membered azaheterocyclic AIEgen

Developing versatile synthetic methodologies with merits of simplicity, efficiency, and environment friendliness for five-membered heterocycles is of incredible importance to pharmaceutical and material science, as well as a huge challenge to synthetic chemistry. Herein, an unexpected regioselective photoreaction to construct a fused five-membered azaheterocycle with an aggregation-induced emission (AIE) characteristic is developed under mild conditions. The formation of the five-membered ring is both thermodynamically and kinetically favored, as justified by theoretical calculation and experimental evidence. Markedly, a light-driven amplification strategy is proposed and applied in selective mitochondria-targeted cancer cell recognition and fluorescent photopattern fabrication with improved resolution. The work not only delivers the first report on efficiently generating a fused five-membered azaheterocyclic AIE luminogen under mild conditions via photoreaction, but also offers deep insight into the essence of the photosynthesis of fused five-membered azaheterocyclic compounds.

Catalyst-Free Multicomponent Cyclopolymerizations of Diisocyanides, Activated Alkynes, and 1,4-Dibromo-2,3-Butanedione: a Facile Strategy toward Functional Polyiminofurans Containing Bromomethyl Groups

Polymers containing iminofuran (PIFs) are rarely reported due to the lack of simple and effective synthesis methods. In this work, a novel multicomponent cyclopolymerization (MCCP) of diisocyanides, activated alkynes, and 1,4-dibromo-2,3-butanedione using catalyst-free one-pot reactions under mild conditions to prepare PIFs containing bromomethyl groups is reported. PIFs with good solubility and thermal stability are obtained with high M_w s (up to 19 600) and good yields (up to 89.5%) under optimized polymerization conditions. The structure of the PIFs is characterized by nuclear magnetic resonance, Fourier transform infrared spectroscopy, and gel permeation chromatography. The photophysical properties indicate that polymers P1a2b3 and P1c2b3 have cluster-triggered emission characteristics. Thin films made from PIFs quickly degrade under UV irradiation. Moreover, the obtained polymers are decorated with bromomethyl and carboxylate groups in the side chain, which can be postfunctionalized to prepare multifunctional materials, such as star branched polymers and biomedical carrier materials. Thus, this work not only enriches the field of polymerization based on isocyanates and activated alkynes but also provides a facile strategy toward functional iminofuran polymers.

Retracted Article: Metal-free [2+2+1] cycloaddition polymerization of alkynes, nitriles, and oxygen atoms to functional polyoxazoles

The metal-free [2+2+1] cycloaddition polymerization of alkynes, nitriles, and O-atoms for the regioselective assembly of highly substituted oxazole compounds has been achieved by the use of iodosobenzene (PhIO) with trifluoromethanesulfonic acid (TfOH). The present reaction could be applied to a facile synthesis of polyoxazoles. In this work, the cycloaddition polymerization of 4-cyano-4'-ethynylbiphenyl and PhIO was developed and modified polyoxazole was prepared. All experimental conditions such as polymerization solvent, temperature, catalyst and time were systematically studied. The structure of the obtained polyoxazole was characterized by GPC and NMR, and its thermal properties were studied by TGA. In addition, the good thermal stability of polyoxazoles with unreacted terminal alkynes and cyano groups makes them potentially useful for modifying resins.

Barbier Self-Condensing Ketyl Polymerization-Induced Emission: A Polarity Reversal Approach to Reversed Polymerizability

Carbon-carbon bond formation through polarity reversal ketyl radical anion coupling of carbonyls has inspired new reaction modes to this cornerstone carbonyl group and played significant roles in organic chemistry. The introduction of this resplendent polarity reversal ketyl strategy into polymer chemistry will inspire new polymerization mode with unpredicted discoveries. Here we show the successful introduction of polarity reversal ketyl approach to polymer chemistry to realize self-condensing ketyl polymerization with polymerization-induced emission. In this polarity reversal approach, it exhibits intriguing reversed polymerizability, where traditional excellent leaving groups are not suitable for polymerization but challenging polymerizations involving the cleavage of challenging C-F and C-CF3 bonds are realized under mild Barbier conditions. This polarity reversal approach enables the polymer chemistry with polarity reversal ketyl mode, opens up a new avenue toward the polymerization of challenging C-X bonds under mild conditions, and sparks design inspiration of new reaction, polymerization, and functional polymer.