Multifunctional Poly(<i>N</i>‑sulfonylamidine)s Constructed by Cu-Catalyzed Three-Component Polycouplings of Diynes, Disulfonyl Azide, and Amino Esters

The development of efficient multicomponent polymerization (MCP) to prepare heteroatom-rich macromolecules, especially those with complicated structures and multifunctionality, is gathering increasing research interest from chemists. In this work, we report a facile one-pot three-component polymerization method to prepare multifunctional polymers. The Cu-catalyzed polycoupling reactions of aromatic diynes, disulfonyl azide, and optically active amino esters proceeded in a mild manner under room temperature, furnishing regular poly­(<i>N</i>-sulfonylamidine)­s with high molecular weights (<i>M</i>_w up to 35 900) and in satisfactory yields (up to 87%). The model compound was synthesized to verify the complete transformation from monomers to the desired polymeric products. All the polymers possess excellent solubility in common organic solvents, good film-forming ability, and high thermal stability. The backbones of the polymers are induced to helically rotate by the optically active chiral amino esters, resulting in the circular dichroism (CD) absorption in the solutions and cast films. The polymers are almost nonemissive in solutions, whereas their nanoaggregates or thin films fluoresce intensely upon photoexcitation, showing a unique phenomenon of aggregation-induced emission (AIE). The thin films of these polymers possess high refractive indices (RI = 1.7327–1.6419) in a wide wavelength region of 400–893 nm and low optical dispersions (<i>D</i> down to 0.0247). Well-resolved two-dimensional fluorescent photopatterns can be generated by UV irradiation of these thin films via a copper photomask in air. This work provides an efficient approach toward synthesizing multifunctional heteroatom-rich polymeric materials, overcoming the drawbacks of conventional polymerizations

Drying and Nondrying Layer-by-Layer Assembly for the Fabrication of Sodium Silicate/TiO₂ Nanoparticle Composite Films

Influences of drying and nondrying steps on structures of layer-by-layer (LbL) assembled sodium silicate/TiO₂ nanoparticles films (donated as silicate/TiO₂ films) have been systematically investigated. The nondrying LbL assembly produces highly porous silicate/TiO₂ films with large thickness. In contrast, the silicate/TiO₂ films fabricated with a drying step after each layer deposition are flat and thin without porous structures. In situ atomic force microscopy (AFM) measurements confirm that the sodium silicate and TiO₂ nanoparticles are deposited in their aggregated forms. A N₂ drying step can disintegrate the aggregated silicate and TiO₂ nanoparticles to produce thin silicate/TiO₂ films with compact structures. Without the drying steps, the aggregated silicate and TiO₂ nanoparticles are well retained, and their LbL assembly produces highly porous silicate/TiO₂ films of large thickness. The highly porous silicate/TiO₂ films are demonstrated to be useful as reusable film adsorbents for dye removal from wastewater because they can adsorb a large amount of cationic organic dyes and decompose them under UV irradiation. The present study is meaningful for exploring drying/nondrying steps for tailoring structure and functions of LbL assembled films

Hyperbranched Poly(aroxycarbonyltriazole)s: Metal-Free Click Polymerization, Light Refraction, Aggregation-Induced Emission, Explosive Detection, and Fluorescent Patterning

The metal-free click polymerization (MFCP) of azide and alkyne has become a powerful tool for the synthesis of functional polytriazoles. Among which, the MFCP of propiolate and azide has been used to prepare functional linear poly­(aroxycarbonyltriazole)­s (PACTs). Their hyperbranched analogues, however, have been rarely prepared. In this paper, hyperbranched PACTs with satisfactory molecular weights and high regioregularities were synthesized in high yields by the MFCP of tripropiolates (<b>1</b>) and tetraphenylethene (TPE)-containing diazide (<b>2</b>) under the optimized reaction conditions without protection from oxygen and moisture. The resultant polymers are soluble in common organic solvents and thermally stable, with 5% loss of their weights at temperatures higher than 330 °C. The polymers exhibit high refractive indices with low chromatic dispersion. Thanks to their contained TPE units, the polymers show the unique feature of aggregation-induced emission, and their aggregates can function as fluorescent sensors for the detection of explosives with the superamplification quenching effect. Furthermore, the polymers can be readily photo-cross-linked, yielding two-dimensional fluorescent patterns with high resolution

Multicomponent Click Polymerization: A Facile Strategy toward Fused Heterocyclic Polymers

We herein report a facile and efficient multicomponent click polymerization route to construct fused heterocyclic polymers with advanced functionalities. Mediated by CuI and trimethylamine at room temperature, diynes, disulfonyl azide, and salicylaldehyde, or <i>o</i>-hydroxylacetophenone undergo polymerizations efficiently and smoothly, affording high-molecular-weight poly­(imino­coumarin)­s (<i>M</i>_w up to 64 600) in satisfactory yields (up to 99%). This multicomponent click polymerization approach enjoys remarkable merits of both multicomponent reactions and click reactions, such as simple operation, high reaction efficiency and isolation yield, mild reaction conditions, and common substrates. The resulting polymers possess outstanding film-forming ability, high thermal stability, and good morphological stability. With tetraphenylethene luminogens embedded in the polymer chains, their solutions fluoresce weakly, whereas their aggregates emit intensely, demonstrative of a typical feature of aggregation-enhanced emission. Furthermore, the obtained polymers with bright film emission and high photosensitivity can be facilely fabricated into well-resolved 2D and 3D patterns by treatment of their films with UV light. Additionally, thanks to the highly polarized conjugated structures, the polymer films possess outstanding refractive indices (1.9284–1.7734) in the visible and near-IR regions (400–893 nm), which can be further adjusted by UV light

One-Pot Three-Component Tandem Polymerization Toward Functional Poly(arylene thiophenylene) with Aggregation-Enhanced Emission Characteristics

The development of efficient multicomponent tandem polymerization is attractive but challenging, owing to the limitations such as the required strict stoichiometric balance, the poor solubility and low molecular weight of the polymer products, etc. In this work, an efficient one-pot three-component polymerization of alkyne, carbonyl chloride and ethyl 2-mercaptoacetate was reported. The polymerization of aromatic diyne (<b>1</b>), diaroyl chloride (<b>2</b>), and ethyl 2-mercaptoacetate (<b>3</b>) catalyzed by Pd­(PPh₃)₂Cl₂/CuI proceeded smoothly under mild conditions at room temperature without strict stoichiometric balance of the monomers, affording poly­(arylene thiophenylene) (P<b>1</b>) with high molecular weights (<i>M</i>_w up to 156 000) in excellent yields (up to 97%). Single crystal structure of model compound <b>4</b> was obtained, aiding in verification of the complete transformation to the desired polymer product. The thiophene-containing conjugated polymer possesses good solubility in common organic solvents, good film-forming ability and high thermal stability. Meanwhile, the polymer shows typical aggregation-enhanced emission behavior: its solution is weakly emissive, but turns to be highly emissive when nanoaggregates or thin films are formed. Furthermore, thin film of P<b>1</b> shows high refractive indices (<i>n</i> = 1.9461–1.6668) in a wide wavelength region of 400–1000 nm, which can be further modulated by UV irradiation. Well-resolved fluorescent photopattern can be generated by exposure of the thin film of P<b>1</b> under UV irradiation through a copper photomask. The polymer also serves as an efficient fluorescent chemosensor for Ru³⁺ with high sensitivity and selectivity, and the quenching constants for the sensing are up to 8.8 × 10⁵ L mol^–1. This work provides a new polymerization concept and an efficient approach toward functional conjugated polymer materials, overcoming the limitations of multicomponent polymerization

A Photostable AIE Luminogen for Specific Mitochondrial Imaging and Tracking

Tracking the dynamics of mitochondrial morphology has attracted much research interest because of its involvement in early stage apoptosis and degenerative conditions. To follow this process, highly specific and photostable fluorescent probes are in demand. Commercially available mitochondria trackers, however, suffer from poor photostability. To overcome this limitation, we have designed and synthesized a fluorescent agent, tetraphenylethene-triphenylphosphonium (TPE-TPP), for mitochondrial imaging. Inherent from the mitochondrial-targeting ability of TPP groups and the aggregation-induced emission (AIE) characteristics of the TPE core, TPE-TPP possesses high specificity to mitochondria, superior photostability, and appreciable tolerance to environmental change, allowing imaging and tracking of the mitochondrial morphological changes in a long period of time

Ethynyl-Capped Hyperbranched Conjugated Polytriazole: Click Polymerization, Clickable Modification, and Aggregation-Enhanced Emission

Cu­(I)-catalyzed azide–alkyne click polymerization, developed based on the click reaction, has become a powerful tool for the construction of functional polytriazoles with linear and hyperbranched structures. This method has, however, rarely been used for the preparation of functional hyperbranched conjugated polytriazoles (<i>hb</i>-CPTA). In this paper, soluble ethynyl-capped <i>hb</i>-CPTA with weight-averaged molecular weight of 39 500 was synthesized in high yield (84.4%) by the Cu­(I)-catalyzed azide–alkyne click polymerization of tetraphenylethene containing diazide [1,2-bis­(4-azidophenyl)-1,2-diphenylethene] and tetrayne [1,1,2,2-tetrakis­(4-ethynylphenyl)­ethane] in equal concentration. By taking advantage of the ethynyl groups on its periphery, the polymer could be efficiently postfunctionalized by azide–alkyne and thiol–yne click reactions. The polymers are thermally stable and loss 5% of their weights at temperatures higher than 340.0 °C. <i>hb</i>-CPTA also possesses high char yield (74.8%) at 800 °C. The polymers feature the unique characteristics of aggregation-enhanced emission. Furthermore, the PL intensities of the <i>hb</i>-CPTA and thiol–yne postfunctionalized polytriazoles increase linearly with water fraction in THF/water mixtures. Thanks to their rigid structures, the polymers could be fabricated into unimolecular nanoparticles with sizes of ca. 100 nm. Thus, this paper provides a powerful method to synthesize soluble ethynyl-capped hyperbranched polymers, which could be a useful platform for preparation of versatile functional polymers via postreactions

A Photostable AIE Luminogen for Specific Mitochondrial Imaging and Tracking

Tracking the dynamics of mitochondrial morphology has attracted much research interest because of its involvement in early stage apoptosis and degenerative conditions. To follow this process, highly specific and photostable fluorescent probes are in demand. Commercially available mitochondria trackers, however, suffer from poor photostability. To overcome this limitation, we have designed and synthesized a fluorescent agent, tetraphenylethene-triphenylphosphonium (TPE-TPP), for mitochondrial imaging. Inherent from the mitochondrial-targeting ability of TPP groups and the aggregation-induced emission (AIE) characteristics of the TPE core, TPE-TPP possesses high specificity to mitochondria, superior photostability, and appreciable tolerance to environmental change, allowing imaging and tracking of the mitochondrial morphological changes in a long period of time

A Photostable AIE Luminogen for Specific Mitochondrial Imaging and Tracking

Tracking the dynamics of mitochondrial morphology has attracted much research interest because of its involvement in early stage apoptosis and degenerative conditions. To follow this process, highly specific and photostable fluorescent probes are in demand. Commercially available mitochondria trackers, however, suffer from poor photostability. To overcome this limitation, we have designed and synthesized a fluorescent agent, tetraphenylethene-triphenylphosphonium (TPE-TPP), for mitochondrial imaging. Inherent from the mitochondrial-targeting ability of TPP groups and the aggregation-induced emission (AIE) characteristics of the TPE core, TPE-TPP possesses high specificity to mitochondria, superior photostability, and appreciable tolerance to environmental change, allowing imaging and tracking of the mitochondrial morphological changes in a long period of time

Specific Fluorescence Probes for Lipid Droplets Based on Simple AIEgens

Lipid droplets (LDs), as dynamic complex organelles, are involved in various physiological processes, and their numbers and activity are related to many diseases, even cancer. Hence, locating and concentration monitoring of LDs are very important to scientific bioresearch and health care. In this work, we prepared two simple luminogens (FAS and DPAS) via very facile synthetic procedures and purification. They feature aggregation-induced emission and excited state intramolecular proton transfer characteristics. They exhibit large Stokes shifts and bright orange and yellow emissions in the aggregated state, and the emissions can be reversibly turned “off” and “on” for many cycles by controlling buffer pH values. Both FAS and DPAS are cytocompatible and can selectively accumulate in and light up the LDs in living cells with superior resolution and high contrast. They also outperform the commercial LD probes in terms of photostability. Combining the advantages of high LD-specificity, good biocompatibility, surperb photostability, and low preparation cost, FAS and DPAS may become powerful tools to the study on LDs-related intracellular activities, such as LDs-based pathology and pharmacology