The development of effective strategies for fabrication of fluorescent organic nanoparticles (FONs) with an aggregation‐induced emission (AIE) feature has an important impact on the biomedical applications of these AIE‐active FONs. In the current work, an ultrafast strategy for fabricating AIE‐active FONs is developed through a “one‐pot” microwave‐assisted, catalysts‐free, and solvent‐free Kabachnik–Fields (KF) reaction for the first time. It is demonstrated that such organophosphorous‐containing AIE‐active block polymers can be synthesized within 2 min under air atmosphere through the microwave‐assisted KF reaction. These polymers show amphiphilic properties and can self‐assemble into mPEG‐CHO‐Phe‐NH2‐DEP FONs, which display high water dispersibility and desirable optical properties. Biological evaluation results suggest that the mPEG‐CHO‐Phe‐NH2‐DEP FONs exhibit low toxicity and are potential for biological imaging applications. More importantly, many other multifunctional AIE‐active FONs can also be fabricated through the strategy described in this work owing to the universality of KF reaction. Besides, combined with the excellent properties of mPEG‐CHO‐Phe‐NH2‐DEP FONs, it is believed that such microwave‐assisted KF reaction shall be an effective route for designing various AIE‐active nanomaterials for different biomedical applications.
Driven by the high demand for sensitive and specific tools for optical imaging, fluorescent nanoprobes with various working mechanisms and advanced functionalities are flourishing at an incredible speed. This work reports the design and fabrication of aggregation‐induced emission (AIE)‐active fluorescent organic nanoparticles (FNPs) via forming dynamic phenyl borate between diol containing hydrophobic AIE dye (APD‐PhCHO) and phenylboronic acid pendant hydrophilic polymers (PEGMA‐VPBA) within 30 min. The final AIE‐active APD‐PhCHO‐PEGMA‐VPBA FNPs display high water dispersibility and strong fluorescence emission because of their amphiphilic properties and AIE feature. Biological evaluation suggests that APD‐PhCHO‐PEGMA‐VPBA FNPs possess negative effect on HeLa cells and desirable optical properties for biological imaging. More importantly, phenyl borate is a dynamic bond with pH and glucose responsiveness. Furthermore, different functions can be designed and introduced into these AIE‐active systems through adoption of different monomers for good applicability of free radical polymerization. Therefore, this work provides a novel platform for preparation of multifunctional AIE‐active nanosystems with responsiveness for various biomedical applications.
Since the development of supramolecular chemical biology, self‐organised nano‐architectures have been widely explored in a variety of biomedical applications. Functionalized synthetic molecules with the ability of non‐covalent assembly in an aqueous environment are typically able to interact with biological systems and are therefore especially interesting for their use in theranostics. Nanostructures based on π‐conjugated oligomers are particularly promising as theranostic platforms as they bear outstanding photophysical properties as well as drug loading capabilities. This Feature Article provides an overview on the recent advances in the self‐assembly of intrinsically fluorescent nanoparticles from π‐conjugated small molecules such as fluorene or perylene based chromophores for biomedical applications.
A series of fluorene‐based conjugated polymers containing the aggregation‐induced emissive (AIE)‐active tetraphenylethene and dicarboxylate pseudocrown as a receptor exhibits a unique dual‐mode sensing ability for selective detection of lead ion in water. Fluorescence turn‐off and turn‐on detections are realized in 80%–90% and 20% water in tetrahydrofuran (THF), respectively, for lead ion with a concentration as low as 10−8 m .
The synthesis, tunable thermoresponsive properties, and self‐assembly of dual redox and thermoresponsive double hydrophilic block copolymers having pendant disulfide linkages (DHBCss) are reported. Well‐defined DHBCss composed of a hydrophilic poly(ethylene oxide) block and a dual thermo‐ and reduction‐responsive random copolymer block containing pendant disulfide linkages are synthesized by atom transfer radical polymerization. Their lower critical solution temperature (LCST) transitions are adjusted through modulating pendant hydrophobic–hydrophilic balance with disulfide–thiol–sulfide chemistry. Further, these DHBCss derivatives are converted to disulfide‐crosslinked nanogels at temperatures above LCST through temperature‐driven self‐assembly and in situ disulfide crosslinking. They exhibit enhanced colloidal stability and further reduction‐responsive degradability, thus demonstrating versatility of dual thermo‐ and reduction‐responsive smart materials.
Bilayer photomechanical films are fabricated by depositing one layer of molecular azobenzene chromophores onto flexible low‐density polyethylene substrates. The photoinduced bending and unbending behavior of five azobenzene derivatives including azobenzene, 4‐hydroxy‐azobenzene, 4‐((4‐hydroxyphenyl)diazenyl)bezoitrile, 4‐((4‐methoxyph‐enyl)diazenyl)phenol, and 4‐(phenyldiazenyl)phenol is systematically studied by considering the incident light intensity and the thickness of the coated chromophore layers. Precise control of photoinduced curling of the bilayer film is successfully achieved upon irradiation with two beams of UV light, and the curled films can be recovered by thermal relaxation in the dark. The easily fabricated bilayer films show fast photomechanical response, strong photoinduced stress, and stability similar to crosslinked polymeric films.
Core cross‐linked star (CCS) polymers become increasingly important in polymer science and are evaluated in many value‐added applications. However, limitations exist to varied degrees for different synthetic methods. It is clear that improvement in synthetic efficiency is fundamental in driving this field moving even further. Here, the most recent advances are highlighted in synthetic strategies, including cross‐linking with cross‐linkers of low solubility, polymerization‐induced self‐assembly in aqueous‐based heterogeneous media, and cross‐linking via dynamic covalent bonds. The understanding of CCS polymers is also further refined to advocate their role as an intermediate between linear polymers and polymeric nanoparticles, and their use as interfacial stabilizers is rationalized within this context.
Artificial special wetting surfaces have drawn much interest due to their important applications in many fields. Nevertheless, tremendous challenges still remain for the fabrication of wetting surfaces with durable and self‐healing properties. Here, recent progress of durable, self‐healing wetting surfaces is highlighted by discussing the fabrications of several typical wetting surfaces including superhydrophobic surfaces, superamphiphobic surfaces, underwater superoleophobic surfaces, and high hydrophilic antifouling surfaces based on expertise and related research experience. To conclude, some perspectives on the future research and development of these special wetting surfaces are presented.
Novel redox‐responsive polymeric nanogels that allow highly efficient enzyme encapsulation and reversible modulation of enzyme activity are developed. The nanogel synthesis and encapsulation of enzyme are performed simultaneously via in situ crosslinking of pyridyldisulfide‐functionalized water‐soluble reactive copolymers, which are synthesized via reversible addition–fragmentation chain transfer copolymerization. Obtained nanogels with loaded cellulase demonstrate very good colloidal stability in aqueous solutions. The enzymatic activity of cellulase is greatly reduced when encapsulated in the nanogels and rapidly recovered in 10 × 10−3 m dithiothreitol solution. Fluorescence resonance energy transfer (FRET)‐based experiments indicate that the recovered enzymatic activity is mainly ascribed to the release of the enzyme due to the degradation of the disulfide crosslinking network after addition of dithiothreitol (DTT), instead of the enhanced substrate transport rate. The developed enzyme immobilization method opens new possibilities for reversible activation/deactivation of enzymes and opens up new directions for targeted protein therapy and biotechnology applications.
In this research, the synthesis of boron‐ketoiminate‐containing polymers is reported with large molecular weights ( = 20 000) and their optical properties are examined by UV–vis absorption and photoluminescence spectrometries. It is shown that the polymers exhibit strong emission both in the solution and solid states (ΦPL,THF = 0.46–0.80, ΦPL,film = 0.13–0.38). These optical properties can be explained by a donor–acceptor interaction between the boron ketoiminate and the electron‐donating comonomer such as fluorene or bithiophene. Furthermore, in the solid states, their emission colors can be successfully tuned from blue to orange by the substituents on the nitrogen atom with the difference of the steric hindrance (λPL,THF = 464–546 nm, λPL,film = 486–604 nm).
Polymer‐based crosslinked networks with intrinsic self‐repairing ability have emerged due to their built‐in ability to repair physical damages. Here, novel dual sulfide–disulfide crosslinked networks (s‐ssPxNs) are reported exhibiting rapid and room temperature self‐healability within seconds to minutes, with no extra healing agents and no change under any environmental conditions. The method to synthesize these self‐healable networks utilizes a combination of well‐known crosslinking chemistry: photoinduced thiol‐ene click‐type radical addition, generating lightly sulfide‐crosslinked polysulfide‐based networks with excess thiols, and their oxidation, creating dynamic disulfide crosslinkages to yield the dual s‐ssPxNs. The resulting s‐ssPxN networks show rapid self‐healing within 30 s to 30 min at room temperature, as well as self‐healing elasticity with reversible viscoelastic properties. These results, combined with tunable self‐healing kinetics, demonstrate the versatility of the method as a new means to synthesize smart multifunctional polymeric materials.
Polymer beads have attracted considerable interest for use in catalysis, drug delivery, and photonics due to their particular shape and surface morphology. Electrospinning, typically used for producing nanofibers, can also be used to fabricate polymer beads if the solution has a sufficiently low concentration. In this work, a novel approach for producing more uniform, intact beads is presented by electrospinning self‐assembled block copolymer (BCP) solutions. This approach allows a relatively high polymer concentration to be used, yet with a low degree of entanglement between polymer chains due to microphase separation of the BCP in a selective solvent system. Herein, to demonstrate the technology, a well‐studied polystyrene‐poly(ethylene butylene)–polystyrene triblock copolymer is dissolved in a co‐solvent system. The effect of solvent composition on the characteristics of the fibers and beads is intensively studied, and the mechanism of this fiber‐to‐bead is found to be dependent on microphase separation of the BCP.
Lanthanide‐doped upconversion nanoparticles (UCNPs) have been an emerging and exciting research field in recent years due to their unique luminescent properties of converting near‐infrared light to shorter wavelength radiation. UCNPs offer excellent prospects in luminescent labeling, displays, bioimaging, bioassays, drug delivery, sensors, and anticounterfeiting applications. Along with the abundant studies and rapid progress in this area, UCNPs are promising to be a new class of luminescent probe owing to their special advantages over the conventional organic dyes and quantum dots. Among them, polymers play an important role to improve properties or endow new function of UCNPs such as for matrix materials, water solubility, linking active targeting molecules, biocompatibility, and stimuli‐responsive behavior. This article briefly reviews the compositions, optical mechanisms, architectures of upconversion nanocrystals and highlights the works on various functional UCNPs/polymer nanohybrids as well as many new interesting fruits in applications.
Discovering fluorescence of existing compounds, which are generally regarded as non‐fluorescent, is of important academic and technical significance. This article reports the fluorescence of common compounds containing pyrrolidone ring(s) and their oxidized hydrolyzates. Poly(N‐vinylpyrrolidone) (PVP), polymerized from a very weak fluorescent monomer N‐vinyl‐2‐pyrrolidone (NVP), exhibits strong intrinsic fluorescence. Moreover, the fluorescence of its “hydrolyzate” is dramatically enhanced by about 1000 times. The “hydrolyzate” of N‐methyl‐pyrrolidone (NMP) also exhibits significantly enhanced fluorescence. By studying the chemical structures and fluorescence of the hydrolyzates, the enhanced fluorescence is attributed to the formation of secondary amine oxide. The much stronger fluorescence of the polymers compared to the corresponding small molecular compounds is ascribed to the “aggregation‐induced emission” (AIE) effect of the luminophores. PVP and its oxidized hydrolyzate also show some phenomena different to the common AIE effect. The fluorescence of PVP and its oxidized hydrolyzate shows stimuli response to metal ions and pH values. This study introduces novel fluorescent materials for various potential applications.
The preparation of multifunctional polymers and block copolymers by a straightforward one‐pot reaction process that combines enzymatic transacylation with light‐controlled polymerization is described. Functional methacrylate monomers are synthesized by enzymatic transacylation and used in situ for light‐controlled polymerization, leading to multifunctional methacrylate‐based polymers with well‐defined microstructure.
A new phenacyl‐type photoinitiator based on ethyl carbazole as a long wavelength photoinitiator is developed for free radical polymerization. Phenacyl ethyl carbazolium hexafluoroantimonate (PECH) photoinitiator is synthesized in a two‐step, one‐pot manner by quaternizing ethyl carbazole with phenacyl bromide and subsequent ion exchange reaction with potassium hexafluoroantimonate. Under irradiation, PECH tends to undergo homolytic bond cleavage bringing about initiating free radicals. However, as evidenced by cyclic voltammetry and real‐time photobleaching studies, formation of initiating cationic species is highly unlikely as the photochemically formed charged carbazole units tend to couple.
In this study, a new type of functional, self‐assembled nanostructure formed from porphyrins and polyamidoamine dendrimers based on hydrogen bonding in an aqueous solution is presented. As the aggregates formed are promising candidates for solar‐energy conversion, their photocatalytic activity is tested using the model reaction of methyl viologen reduction. The self‐assembled structures show significantly increased activity as compared to unassociated porphyrins. Details of interaction forces driving the supramolecular structure formation and regulating catalytic efficiency are fundamentally discussed.
Fluorescent polymeric nanoparticles (FPNs) with aggregation‐induced emission (AIE) property have received increasing attention and possess promising biomedical application potential in the recent years. Many efforts have been devoted to the fabrication methodologies of FPNs and significant advance has been achieved. In this contribution, a novel strategy for the fabrication of AIE‐active amphiphilic copolymers is reported for the first time based on the Ce(IV) redox polymerization. As an example, ene group containing AIE‐active dye (named as Phe‐alc) is directly grafted onto a water soluble polymer polyethylene glycol (PEG) in H2O/THF system under low temperature. Thus‐obtained amphiphilic fluorescent polymers will self‐assemble into FPNs with ultra‐low critical micelle concentration, ultra‐brightness, and great water dispersibility. Biological evaluation results suggest that the PEG‐poly(Phe‐alc) possess excellent biocompatibility and can be used for tracing their behavior in cells using confocal laser scanning microscope. These features make PEG‐poly(Phe‐alc) FPNs promising candidates for many biomedical applications, such as cell imaging, drug delivery vehicles, and targeted tracing. More importantly, many other functional groups can also be incorporated into these AIE‐active FPNs through the redox polymerization. Therefore, the redox polymerization should be a facile and effective strategy for fabrication of AIE‐active FPNs.
Covalent triazine‐based frameworks (CTFs) with a graphene‐like layered morphology have been controllably synthesized by the trifluoromethanesulfonic acid‐catalyzed nitrile trimerization reactions at room temperature via selecting different monomers. Platinum nanoparticles are well dispersed in CTF‐T1, which is ascribed to the synergistic effects of the coordination of triazine moieties and the nanoscale confinement effect of CTFs. CTF‐T1 exhibits excellent photocatalytic activity and stability for H2 evolution in the presence of platinum under visible light irradiation (λ ≥ 420 nm). The activity and stability of CTF‐T1 are comparable to those of g‐C3N4. Importantly, as a result of the tailorable electronic and spatial structures of CTFs that can be achieved through the judicial selection of monomers, CTFs not only show great potential as organic semiconductor for photocatalysis but also may provide a molecular‐level understanding of the inherent heterogeneous photocatalysis.
Polymers with pendant phenoxyl radicals are synthesized and the electrochemical properties are investigated in detail. The monomers are polymerized using ring‐opening metathesis polymerization (ROMP) or free‐radical polymerization methods. The monomers and polymers, respectively, are oxidized to the radical either before or after the polymerization. These phenoxyl radicals containing polymers reveal a reversible redox behavior at a potential of −0.6 V (vs Ag/AgCl). Such materials can be used as anode‐active material in organic radical batteries (ORBs).
