The demand for highly efficient solid-state luminophores is continuously growing due to their potential applications in optoelectrical devices, chemosensors, and biological applications. The discovery of luminogens with aggregation-induced emission (AIE) by Tang et al. in 2001 provides a good reponse to this demand. Among the exploited AIE luminogens, AIE-active polymers possess many advantages such as simple synthesis, convenient structrue modifications, and good processability, which offer an extensive platform for scientists and engineers. Herein, the design principles and latest synthetic advancement of AIE-active polymers are summarized, including click polymerization and multicomponent polymerization. Non-conjugated heteroatom-rich polymers were in situ generated and demonstated non-conventional clusteroluminoscence. Advanced applications including fluorescent sensors, stimuli-responsive materials, biological applications, circularly polarized luminescence, and electroluminescence are then introduced in detail. AIE-active polymers display the signal-amplification effect for sensitive and selective response to chemo/bioanalytes or stimuli and enhanced photosensitization effect for cancer theranostics. Retrospecting the expansion of this field can further strengthen our belief that AIE-active polymers are promising for conceptual innovation and technological breakthroughs in the near future.

Recently, polymers with aggregation-induced emission (AIE) effects have attracted significant attention due to their broad applications in luminescence sensors, stimuli responsive materials, electroluminescence devices, etc. In this review, we summarize recent advances concerning AIE polymers. Four types of AIE polymers including end-functionalized polymers, side-chain polymers, main-chain polymers, and other polymers according to the location of AIEgens, are described. Their synthetic preparation, optical property, AIE effects, and applications are also illustrated in this review.

Tetraphenylethylene (TPE) derivatives are typical aggregation-induced emission (AIE) molecules, which have been widely investigated and applicated. The Rathore’s procedures and McMurry reaction are the two frequently used methods for synthesizing the TPE derivatives. The complex processes and low tolerance of active function groups make the TPE with limited structures and properties in some degree. Very recently, a novel strategy, named geminal cross coupling (GCC) reaction, is developed for designing and synthesizing various topological small molecules and polymers with rich optical properties beyond simple TPE compounds, and becomes a powerful synthesis method to AIE materials. This review overviews the current progresses of AIE molecules and polymers prepared by GCC as well as their applications. We believe that GCC reaction will have a bright future in the development of the next generation of tetraarylethylene (TAE)-kind AIE materials.

Organic dyes based hybrid organic-inorganic luminescent nanomaterials with high quantum efficiency, good physical or chemical stability, and favorable biocompatibility, have attracted growing attention recently because of their important applications in the areas of biomedical imaging, chemical sensors, and light-emitting diodes (LEDs). Nevertheless, conventional fluorescence molecules suffer from aggregation-caused quenching (ACQ) when they are doped into inorganic nanomaterials. Aggregation-induced emission (AIE) is an abnormal and intriguing fluorescent phenomenon that has aroused increasing interest for various applications especially in biomedical fields. Compared with conventional organic dyes, the AIE-active molecules will emit more intense fluorescence in their aggregates or solid states. It provides an elegant route to overcome the drawbacks of conventional organic molecules. Over the past few decades, the fabrication and surface modification of various organic-inorganic luminescent composites doped with AIE-active molecules have been reported. Therefore, it is highly desirable to summarize these advances. In this review, recent advances and progress in constructing various AIEgens-doped organic-inorganic hybrid nanocomposites and their subsequent surface modification were summarized. We hope this review could further promote the research of AIE-active functional materials.

Fluorescent vesicles have recently attracted increasing attention because of their potential applications in bioimaging, diagnostics, and theranostics, for example, in vivo study of the delivery and the distribution of active substances. However, fluorescent vesicles containing conventional organic dyes often suffer from the problem of aggregation-caused quenching (ACQ) of fluorescence. Fluorescent vesicles working with aggregation-induced emission (AIE) offer an extraordinary tool to tackle the ACQ issue, showing advantages such as high emission efficiency, superior photophysical stability, low background interference, and high sensitivity. AIE fluorescent vesicles represent a new type of fluorescent and functional nanomaterials. In this review, we summarize the recent advances in the development of AIE fluorescent vesicles. The review is organized according to the chemical structures and architectures of the amphiphilic molecules that constitute the AIE vesicles, i.e., small-molecule amphiphiles, amphiphilic polymers, and amphiphilic supramolecules and supramacromolecules. The studies on the applications of these AIE vesicles as stimuli-responsive vesicles, fluorescence-guided drug release carriers, cell imaging tools, and fluorescent materials based on fluorescence resonance energy transfer (FRET) are also discussed.

Tetraphenylethylene (TPE) and its derivatives, as the widely used aggregation-induced emission (AIE) fluorophores, have attracted rapidly growing interest in the fields of material science and biological technology due to their unique light-emitting mechanism—they are nearly non-emissive in dilute solution but emit brilliant fluorescence in the aggregate state because of the restriction of intramolecular motion. Coordination-driven self-assembly, which provides a highly effective method to put the individual chromophores together, is consistent with the AIE mechanism of TPE. During the past few years, some AIE-active metal-organic coordination complexes have been successfully constructed via coordination-driven self-assembly, and their AIE properties and applications have been investigated. In this review, we survey the recent progress on TPE-based metal-organic coordination complexes and their applications in fluorescence sensors, cell imaging, and light-emitting materials. We will introduce them from three different types of structures: metallacycles, metallacages, and metal-organic frameworks (MOFs).

Room temperature phosphorescence (RTP) has drawn increasing attention for its great potential in practical applications. Polymers with large molecular weights and long chains tend to form coil, which can endow them with a high degree of possible rigidity and result in the much restricted non-radiative transition. Also, the intertwined structure of polymers could isolate the oxygen and humidity effectively, thus reducing the consumption of triplet excitons. In consideration of these points, organic polymers would be another kind of ideal platform to realize RTP effect. This short review summarized the design strategy of the purely organic room temperature phosphorescence polymers, mainly focusing on the building forms of polymers and the corresponding inherent mechanisms, and also gives some outlooks on the further exploration of this field at the end of this paper.

Thermoresponsive fluorescent polymers (TFPs) with unique temperature-dependent luminescent properties are of great importance for the development of new functional devices in recent years. Herein, we facilely synthesized an efficient blue-emissive polymer, abbreviated as PCB-TPE, using tetraphenylethene (TPE) as the main building block. PCB-TPE is thermally stable with a novel property of aggregation induced emission (AIE). The thermoresponsive property and mechanism of PCB-TPE were investigated. Its emission shows temperature-dependent features and reveals fine details in the thermal transitions from −10 °C to 60 °C. The polymer offers a platform for the development of efficient luminescent materials for further biological and optoelectronic applications.

Near-infrared (NIR) nanoparticles (NPs) based on fluorescence resonance energy transfer (FRET) were prepared by co-encapsulation of a red aggregation-induced emission (AIE) molecule, 2-(4-bromophenyl)-3-(4-(4-(diphenylamino)styryl)phenyl)fumaronitrile (TB), and a commercial NIR fluorescence dye, silicon 2,3-naphthalocyanine bis(trihexylsilyloxide) (NIR775) with an amphiphilic polymer poly(styrene-co-maleic anhydride) (PSMA). The surface of the NPs, PSMA@TB/NIR775, was modified with poly(ethylene glycol) (PEG) to increase the in vivo biocompatibility of the NPs. The PSMA@TB/NIR775 NPs showed a strong NIR (780 nm) narrow emission and excellent two-photon absorption property. Moreover, the NPs exhibited good monodispersity, stability, and low cytotoxicity. Under the excitation of a 1040 nm femtosecond (fs) laser, the emission peaks at 680 nm of TB and 780 nm of NIR775 excited by FRET were obtained. We utilized PSMA@TB/NIR775 NPs as fluorescent contrast agents for two-photon excited NIR microscopic imaging, and good NIR imaging effect of mouse brain vasculature was obtained with the imaging depth of about 150 µm. The FRET strategy by co-encapsulating AIE molecule and NIR dye will be helpful in preparing more narrow emission NIR probes for deep-tissue biological imaging.

In recent years, nonconventional luminogens free of aromatic groups have attracted extensive attention due to their academic importance and promising wide applications. Whilst previous studies generally focused on fluorescence from aliphatic amine or carbonyl-containing systems, less attention has been paid to room temperature phosphorescence (RTP) and the systems with predominant oxygen functionalities. In this work, photophysical properties of the polyhydroxy polymers, including microcrystalline cellulose (MCC), 2-hydroxyethyl cellulose (HEC), hydroxypropyl cellulose (HPC), and cellulose acetate (CA), were studied and compared. While MCC, HEC, and HPC solids showed bright emission alongside distinct RTP, CA demonstrated relatively low intensity of solid emission without noticeable RTP. Their emissions were explained in terms of the clustering-triggered emission (CTE) mechanism and conformation rigidification. Additionally, on account of its intrinsic emission, concentrated HEC aqueous solution could be used as the probe for the detection of 2,4,6-trinitrophenol (TNP).

A diamine (WuFDA) containing vertical rigid non-planar conjugated fluorene moiety and low polarizability group (C―F) was designed and synthesized through three steps of reactions (halogenated reaction, Suzuki coupling reaction, and reduction reaction). Four kinds of high performance functional polyimides (WuFPI-6F, WuFPI-BP, WuFPI-BT, and WuFPI-PM) were thus prepared by the condensation polymerization of WuFDA with four commercial dianhydride 6FDA, BPDA, BTDA, and PMDA, respectively. The polyimides exhibited low dielectric constant, excellent thermal stability, outstanding solubility, good film-forming property, and mechanical properties. The dielectric constants of the polyimides were in the range of 2.28−2.88 (f = 10⁴ Hz). The 5% weight-loss temperatures (T_d5%) in nitrogen were in the range of 555−584 °C, and the glass transition temperatures (T_g) were in the range of 408−448 °C. The weight loss of WuFPI-BP maintaining at 450 and 500 °C for half an hour was only 0.33% and 1.26%, respectively. All the WuFPIs could be dissolved in almost all organic solvents, even chloroform. The tensile strength and tensile modulus of these films were in the ranges of 78.6−85.7 MPa and 3.1−3.2 GPa, respectively. In addition, the polyimides displayed light color with special fluorescent and resistive switching (ON-OFF) characteristics; the maximum fluorescence emission was observed at 422−424 nm in NMP solution and at 470−548 nm in film state. The memory devices with the configuration of indium tin oxide/WuFPIs/aluminum (ITO/WuFPIs/Al) exhibited distinct volatile memory characteristics of static random access memory (SRAM), with an ON/OFF current ratio of 10⁵−10⁶. These functional polyimides showed attractive potential applications in the field of high performance flexible polymer photoelectronic devices or polymer memory devices.

Hyperbranched polymer with highly branched three-dimensional topological structure, a large number of end groups, and multifaceted functionalities have gained much attention, while polymers with aggregation-induced emission (AIE) properties become a group of popular luminescent materials recently. The design and synthesis of AIE-active hyperbranched polymers, which combine the advantages of these two types of materials, are attractive but challenging. In this work, four hyperbranched poly(tetrahydropyrimidine)s were synthesized from the metal-free room temperature multicomponent tandem polymerization of diester group-activated internal alkyne, polyfunctional aromatic amines, and formaldehyde in methanol under the catalysis of acetic acid. Through different monomer combination and controlling the monomer loading order, hyperbranched polymers with various topological structures as well as sequences of different functional groups in the polymer backbone were obtained with high molecular weights (up to 3.0 × 10⁴ g/mol) in high yields (up to 98%). The hyperbranched poly(tetrahydropyrimidine) emitted faintly in solution, while its luminescence was notably enhanced in the aggregated state, suggesting its typical aggregation-induced emission property. It is anticipated that the multicomponent polymerization may provide a synthetic platform for the construction of hyperbranched polyheterocycles with diverse structures and functionalities.