Cellulose nanofibers-based composite film with broadening MXene layer spacing and rapid moisture separation for humidity sensing and humidity actuators

Based on the basic idea of expanding the interlayer spacing of MXene, utilizing the effect of gallic acid-modified cellulose nanofibers for rapid moisture separation, the flexible sensing and driving composite film with a perfect balance among humidity signal response and mechanical properties was prepared. Inspired by the stacking of autumn fallen leaves, the cellulose nanofibers-based composite films were formed by self-assembly under vacuum filtration of blending gallic acid-modified cellulose nanofibers with MXene. The enhanced mechanical properties (tensile strength 131.1 MPa, puncture load 0.88 N, tearing strength 165.55 N/mm, and elongation at break 16.14 %), humidity sensing (the stable induced voltage 63.7 mV and response/recovery time 3.2/5.1 s), and humidity driving (154.7° bending angle) properties were observed. The synergistic effect of hydrogen bonds, the "pinning effect" arising from the side chains, and the hierarchical layered microstructure contributed to the enhanced performance. This work exemplifies the application of green natural product for preparing intelligent sensing, wearable devices, and biomimetic robots.

Preparation and Application of Amino-Terminated Hyperbranched Magnetic Composites in High-Turbidity Water Treatment

In order to separate the colloidal in high-turbidity water, a kind of magnetic composite (Fe3O4/HBPN) was prepared via the functional assembly of Fe3O4 and an amino-terminal hyperbranched polymer (HBPN). The physical and chemical characteristics of Fe3O4@HBPN were investigated by different means. The Fourier Transform infrared spectroscopy (FTIR) spectra showed that the characteristic absorption peaks positioned at 1110 cm-1, 1468 cm-1, 1570 cm-1 and 1641 cm-1 were ascribed to C-N, H-N-C, N-H and C=O bonds, respectively. The shape and size of Fe3O4/HBPN showed a different and uneven distribution; the particles clumped together and were coated with an oil-like film. Energy-dispersive spectroscopy (EDS) displayed that the main elements of Fe3O4/HBPN were C, N, O, and Fe. The superparamagnetic properties and good magnetic response were revealed by vibrating sample magnetometer (VSM) analysis. The characteristic diffraction peaks of Fe3O4/HBPN were observed at 2θ = 30.01 (220), 35.70 (311), 43.01 (400), 56.82 (511), and 62.32 (440), which indicated that the intrinsic phase of magnetite remained. The zeta potential measurement indicated that the surface charge of Fe3O4/HBPN was positive in the pH range 4-10. The mass loss of Fe3O4/HBPN in thermogravimetric analysis (TGA) proved thermal decomposition. The -C-NH2 or -C-NH perssad of HBPN were linked and loaded with Fe3O4 particles by the N-O bonds. When the Fe3O4/HBPN dosage was 2.5 mg/L, pH = 4-5, the kaolin concentration of 1.0 g/L and the magnetic field of 3800 G were the preferred reaction conditions. In addition, a removal efficiency of at least 86% was reached for the actual water treatment. Fe3O4/HBPN was recycled after the first application and reused five times. The recycling efficiency and removal efficiency both showed no significant difference five times (p > 0.05), and the values were between 84.8% and 86.9%.

Hyperbranched polysiloxane-based probe with enhanced lipophilicity for visualizing ONOO- fluctuations in endoplasmic reticulum

The endoplasmic reticulum, a cellular signaling regulator, participates in the synthesis and secretion of many proteins, glycogen, lipids and cholesterol substances. Peroxynitrite (ONOO^-) is a highly oxidative and nucleophilic agent. Abnormal fluctuations of ONOO^- induce oxidative stress in the endoplasmic reticulum, further disrupting the normal function of protein folding and transport and glycosylation modification, ultimately leading to neurodegenerative diseases, cancer and Alzheimer's disease. Up to now, most probes have tended to achieve targeting functions by introducing specific targeting groups. However, this approach increased the difficulty of the construction process. Therefore, a simple and efficient construction strategy for fluorescent probes with excellent specificity targeting the endoplasmic reticulum is lacking. To overcome this difficulty and put forward an efficient design strategy for the endoplasmic reticulum targeted probes, in this paper, we constructed alternating rigid and flexible polysiloxane-based hyperbranched polymeric probes (Si-Er-ONOO) by bonding perylenetetracarboxylic anhydride and silicon-based dendrimers for the first time. Efficient and specific targeting of the endoplasmic reticulum was successfully achieved by the excellent lipid solubility of Si-Er-ONOO. Furthermore, we observed different effects of metformin and rotenone on the changes of ONOO^- volatility in the cellular and zebrafish internal environment by Si-Er-ONOO. We believe that Si-Er-ONOO will expand the application of organosilicon hyperbranched polymeric materials in bioimaging and provide an excellent indicator of reactive oxygen species fluctuations in biological systems.

Drug Self-Delivery Systems: Molecule Design, Construction Strategy, and Biological Application

Drug self-delivery systems (DSDSs) offer new ways to create novel drug delivery systems (DDSs). In typical DSDSs, therapeutic reagents are not considered passive cargos but active delivery agents of actionable targets. As an advanced drug delivery strategy, DSDSs with positive cooperativity of both free drugs and nanocarriers exhibit the clear merits of unprecedented drug-loading capacity, minimized systemic toxicity, and flexible preparation of nanoscale deliverables for passive targeted therapy. This review highlights the recent advances and future trends in DSDSs on the basis of two differently constructed structures: covalent and noncovalent bond-based DSDSs. Specifically, various chemical and architectural designs, fabrication strategies, and responsive and functional features are comprehensively discussed for these two types of DSDSs. In addition, additional comments on the current development status of DSDSs and the potential applications of their molecular designs are presented in the corresponding discussion. Finally, the promising potential of DSDSs in biological applications is revealed and the relationship between preliminary molecular design of DSDSs and therapeutic effects of subsequent DSDSs biological applications is clarified.

An AB2 -Type Hyperbranched Supramolecular Polymer Based on Calix[4]pyrrole Anion Recognition: Construction, Stimuli-Responsiveness, and Morphology Tuning

An AB₂ -type monomer comprised of a calix[4]pyrrole skeleton and alternating bis-carboxylate units is reported and used for the construction of a novel supramolecular hyperbranched polymer based on anion recognition ability of calix[4]pyrrole. ¹ H-, DOSY-NMR spectroscopy, viscosity measurements, and dynamic light scattering techniques are used for the characterization of the supramolecular hyperbranched polymer exhibiting thermo-, pH-, and chemical responsiveness, as well as concentration dependent morphology tune as inferred from electron microscopy analyses. The present study enriches the field of supramolecular polymers with a new construction motif, building block, and provides a simple approach for the fabrication of smart polymer material with multi-responsiveness and -morphologies. This article is protected by copyright. All rights reserved.

Fluorescence Resonance Energy Transfer Measurements in Polymer Science: A Review

Fluorescence resonance energy transfer (FRET) is a non-invasive characterization method for studying molecular structures and dynamics, providing high spatial resolution at nanometer scale. Over the past decades, FRET-based measurements are developed and widely implemented in synthetic polymer systems for understanding and detecting a variety of nanoscale phenomena, enabling significant advances in polymer science. In this review, the basic principles of fluorescence and FRET are briefly discussed. Several representative research areas are highlighted, where FRET spectroscopy and imaging can be employed to reveal polymer morphology and kinetics. These examples include understanding polymer micelle formation and stability, detecting guest molecule release from polymer host, characterizing supramolecular assembly, imaging composite interfaces, and determining polymer chain conformations and their diffusion kinetics. Finally, a perspective on the opportunities of FRET-based measurements is provided for further allowing their greater contributions in this exciting area.

Supramolecular topological hydrogels: from material design to applications

Supramolecular topological hydrogels are constructed by introducing different dynamic topological structures into polymeric networks and thus exhibit a wide variety of stimuli-responsive properties and versatile applications.

Supramolecular hyperbranched polymer gels based on pillar[5]arene and their applications in removal of micropollutants from water

Two kinds of pillar[5]arene-based supramolecular hyperbranched polymer gels were constructed and applied to efficiently remove micropollutants from water.

Hierarchical self-assembly induced supramolecular polymer helical nanowires with white circularly polarized luminescence

A novel CPL-active supramolecular helical nanowires (SHNW) was successfully constructed, via the hierarchical self-assembly of supramolecular coordination polymers. The CPL colors of the resultant SHNWs are drastically regulated from blue...

Understanding of supramolecular emulsion interfacial polymerization in silico

The composition and structure of a membrane determine its functionality and practical application. We study the supramolecular polymeric membrane prepared by supramolecular emulsion interfacial polymerization (SEIP) on the oil-in-water droplet via the computer simulation method. The factors that may influence its structure and properties are investigated, such as the degree of polymerization and molecular weight distribution (MWD) of products in the polymeric membranes. We find that the SEIP can lead to a higher total degree of polymerization as compared to the supramolecular interfacial polymerization (SIP). However, the average chain length of products in the SEIP is lower than that of the SIP due to its obvious interface curvature. The stoichiometric ratio of reactants in two phases will affect the MWD of the products, which further affects the performance of the membranes in practical applications, such as drug release rate and permeability. Besides, the MWD of the product by SEIP obviously deviates from the Flory distribution as a consequence of the curvature of reaction interface. In addition, we obtain the MWD for the emulsions whose size distribution conforms to the Gaussian distribution so that the MWD may be predicted according to the corresponding emulsion size distribution. This study helps us to better understand the controlling factors that may affect the structure and properties of supramolecular polymeric membranes by SEIP.

Platinum-Containing Supramolecular Drug Self-Delivery Nanomicelles for Efficient Synergistic Combination Chemotherapy

Supramolecular drug self-delivery systems (SDSDSs) involving active drugs as building blocks linked by supramolecular interactions have been well defined as an advanced chemotherapy strategy. However, the lack of detecting release of drugs from SDSDSs at specific tumor sites inevitably leads to unsatisfactory therapeutic effects, owing to the lack of information regarding the administration of these drugs. In this work, predesigned platinum-containing supramolecular drug self-delivery nanomicelles (SDSDNMs) were employed to synchronously realize drug monitoring by computed tomography imaging, immediately reflecting the evolution of drug release and real-time treatment at the tumor site. The appropriate administration dosage (1.2 mg mL^-1,100 μL) and the injection interval (once every 3 days) needed to guide the antitumor activity of SDSDNMs were then defined, thereby attaining the aim of efficient synergistic combination chemotherapy. In vivo tumor inhibition and histological analyses showed that SDSDNMs exhibited a strong tumor inhibition effect and good safety with respect to normal organs. Such a supramolecular drug self-delivery strategy with monitored functions may offer new potential opportunities for application in the field of synergistic combination chemotherapy.

A permanent covalent bond-crosslinked thermosetting polymer with room-temperature autonomous self-healing performance

A room-temperature autonomous self-healing thermosetting polymer was prepared by crosslinking hydroxylated hyperbranched polymer with permanent covalent bonds for the first time.

Stimuli-Responsive Internally Ion-Paired Supramolecular Polymer Based on a Bis-pillar[5]arene Dicarboxylic Acid Monomer

A novel bis-pillar[5]arene dicarboxylic acid self-assembles in the presence of 1,12-diaminododecane to yield overall neutral, internally ion-paired supramolecular polymers. Their aggregation, binding mode, and morphology can be tuned by external stimuli such as solvent polarity, concentration, and base treatment.

β-Cyclodextrin modified Pt(II) metallacycle-based supramolecular hyperbranched polymer assemblies for DOX delivery to liver cancer cells

Despite the widespread clinical application of chemotherapeutic anticancer drugs, their adverse side effects and inefficient performances remain ongoing issues. A drug delivery system (DDS) designed for a specific cancer may therefore overcome the drawbacks of single chemotherapeutic drugs and provide precise and synergistical cancer treatment by introducing exclusive stimulus responsiveness and combined chemotherapy properties. Herein, we report the design and synthesis of a supramolecular drug delivery assembly 1 constructed by orthogonal self-assembly technique in aqueous media specifically for application in liver cancer therapy. Complex 1 incorporates the β-cyclodextrin host molecule-functionalized organoplatinum(II) metallacycle 2 with two specific stimulus-responsive motifs to the signaling molecule nitric oxide (NO), in addition to the three-armed polyethylene glycol (PEG) functionalized ferrocene 3 with redox responsiveness. With this molecular design, the particularly low critical aggregation concentration (CAC) of assembly 1 allowed encapsulation of the commercial anticancer drug doxorubicin (DOX). Controlled drug release was also achieved by morphological transfer via a sensitive response to the endogenous redox and NO stimuli, which are specifically related to the microenvironment of liver tumor cells. Upon combination of these properties with the anticancer ability from the platinum acceptor, in vitro studies demonstrated that DOX-loaded 1 is able to codeliver anticancer drugs and exhibit therapeutic effectiveness to liver tumor sites via a synergistic effect, thereby revealing a potential DDS platform for precise liver cancer therapeutics.

Acceptor-induced cooperative supramolecular co-assembly with emissive charge-transfer for advanced supramolecular encryption

A novel acceptor-induced cooperative supramolecular co-assembly based on a dendritic electron donor and 1,2,4,5-tetracyanobenzene acceptor has been successfully developed. The resulting co-assembly is capable of displaying emissive charge transfer properties and intriguing vapo-fluorochromic behaviors, which can be used for supramolecular encryption applications with reversible authentication.

Functional supramolecular gels based on pillar[n]arene macrocycles

Supramolecular gels constructed from low-molecular-weight gelators via noncovalent interactions have received increasing attention. The rapid development of stimuli-responsive supramolecular gels with attractive properties is highly desirable to meet the ever-growing demand of materials science and chemistry. The inherent reversible and dynamic nature of noncovalent interactions in supramolecular gels endows the materials with sensing, processing, and actuating functions in response to specific environmental changes and offers them great potential in flexible biomaterials and intelligent devices. In particular, pillar[n]arenes with symmetrical pillar-shaped architectures have been recognized as an emerging class of synthetic macrocycles after crown ethers, cyclodextrins, calixarenes, and cucurbiturils, and proven to be excellent candidates for the fabrication of functional supramolecular gels due to their many advantages including facile synthesis, diverse functionalization, and appealing host-guest properties. This review provides a comprehensive overview of recent progress in supramolecular gels involving pillar[n]arenes and their derivatives as synthetic macrocyclic arenes, from the viewpoints of the synthetic approach, controllable assembly, stimuli-responsiveness, and functions. Perspectives of this burgeoning field of research are also given at the end.

Hyperbranching-Enhanced-Emission Effect Discovered in Hyperbranched Poly(4-(cyanomethyl)phenyl methacrylate)

To disclose the effect of architecture over fluorescence behaviors of polymers, linear and hyperbranched poly(4-(cyanomethyl)phenyl methacrylate)s (PCPMAs) were synthesized by using atom transfer radical polymerization (ATRP). Compared to linear PCPMAs with weakly AIE (AIE: aggregation-induced-emission) characteristics and small-molecule analogues of 4-(cyanomethyl)phenyl isobutyrate (CPB) with ACQ (ACQ: aggregation-caused-quenching) behaviors, hyperbranched PCPMA showed dramatically stronger fluorescence at both solution and solid states and more significant AIE characteristics, which were further enhanced by increasing the branching degree, indicating a significant hyperbranching-enhanced-emission effect (HEE). The HEE effect was attributed to the strong promotion of hyperbranched architecture over the formation of a nitrile group cluster with through-space conjugation (TSC). The HEE effect provided a promising methodology to construct efficient nontraditional fluorescent polymers without large-conjugated, rigid, and planar emitter groups.

Nanocrystal Encapsulation, Release and Application Based on pH-Sensitive Covalent Dynamic Hyperbranched Polymers

A new strategy for nanocrystal encapsulation, release and application based on pH-sensitive covalent dynamic hyperbranched polymers is described. The covalent dynamic hyperbranched polymers, with multi-arm hydrophobic chains and a hydrophilic hyperbranched poly(amidoamine) (HPAMAM) core connected with pH-sensitive imine bonds (HPAMAM–DA), could encapsulate CdTe quantum dots (QDs) and Au nanoparticles (NPs). Benefiting from its pH response property, CdTe QDs and Au NPs encapsulated by HPAMAM–DA could be released to aqueous phase after imine hydrolysis. The released CdTe/HPAMAM and Au/HPAMAM nanocomposites exhibited excellent biological imaging behavior and high catalytic activities on p-nitrophenol hydrogenation, respectively.

Supramolecular nanoscale drug-delivery system with ordered structure

Supramolecular chemistry provides a means to integrate multi-type molecules leading to a dynamic organization. The study of functional nanoscale drug-delivery systems based on supramolecular interactions is a recent trend. Much work has focused on the design of supramolecular building blocks and the engineering of supramolecular integration, with the goal of optimized delivery behavior and enhanced therapeutic effect. This review introduces recent advances in supramolecular designs of nanoscale drug delivery. Supramolecular affinity can act as a main driving force either in the self-assembly of carriers or in the loading of drugs. It is also possible to employ strong recognitions to achieve self-delivery of drugs. Due to dynamic controllable drug-release properties, the supramolecular nanoscale drug-delivery system provides a promising platform for precision medicine.

Dynamic Adaptive Two-Dimensional Supramolecular Assemblies for On-Demand Filtration

The construction of synthetic two-dimensional (2D) materials designates a pathway to the versatile chemical functionality by spatial control. However, current 2D materials with intelligence of stimuli-responsibility and adaptiveness have been unfledged. The approach reported here uses a supramolecular strategy to achieve the dynamic non-covalent self-assembly of a rationally designed small molecule monomer, producing large-area, ultra-thin, porous 2D supramolecular assemblies, which are solution-processable in aqueous solution. Importantly, the 2D supramolecular assemblies exhibit distinct adaptive capability to automatically regulate their network density and pore diameters in response to environmental temperature change, which could be developed into an "on-demand" filtration application for nanoparticles. Meanwhile, the 2D supramolecular assemblies can also perform reversible degradation/reformation by photo-irradiation. Our results not only show the simplicity, reliability, and effectiveness of supramolecular strategies in the construction of 2D materials with practical sizes, but also push the dynamic alterability and adaptation features from supramolecular assemblies toward 2D materials.

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2D supramolecular assemblies combine large area, nano-thickness and water solubility

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The 2D assemblies can perform reversible expansion/contraction to tune pore sizes

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The 2D material can be used for on-demand nanoparticles filtration

Formation of a Supramolecular Polymeric Adhesive via Water-Participant Hydrogen Bond Formation

A supramolecular polymeric adhesive was prepared from non-viscous, non-polymeric materials by water-participant hydrogen bonds. Pt-pyridine coordination and water-crown ether hydrogen bonding combine to effect the supramolecular polymerization. The supramolecular polymeric adhesive displays strong, reversible adhesion to hydrophilic surfaces, a property that forecasts the application of hydrogen bonding in advanced supramolecular materials.

A degradable low molecular weight monomer system with lower critical solution temperature behaviour in water

A degradable thermo-responsive system was prepared and investigated. The degradation behaviour induced by the cleavage process of the thermo-sensitive crown ethers effectively altered the thermo-responsiveness.

Pillararene-based supramolecular polymers

Pillararenes, as a new type of macrocyclic hosts, possess columnar structures and electron-rich cavities. Pillararenes not only recognize suitable cations, but also bind many neutral molecules. Due to the easy modification of pillararenes, various functional groups can be conveniently attached to the rim of pillararenes to provide suitable interaction sites, and the modified pillararenes even bind anionic guests. Thus, pillararenes and their derivatives have presented intriguing and unique host-guest recognition nature in the past few years, which make them ideal building blocks for the preparation of supramolecular polymers. Pillararene-based supramolecular polymers (PSPs) not only possess many merits of traditional covalent polymers but also have many specific properties, such as self-reparability, degradability, and self-adaptation. This feature paper gives an overview of the preparation of PSPs and covers recent research advance and future trends of pillararene-based host-guest pairs, assembly methods, topological architectures, stimuli-responsiveness, and functional features. We expect that the review will be helpful to researchers working in the fields of supramolecular chemistry and polymer science.

Preparation of cross-linked supramolecular polymers based on benzo-21-crown-7/secondary ammonium salt host-guest interactions

We found that TC7 not only self-assembles into one-dimensional supramolecular aggregates in chloroform, but also forms cross-linked supramolecular polymers via host-guest complexation between benzo-21-crown-7 and secondary ammonium salts. Compared with one-dimensional linear supramolecular polymers, soft and long viscous fibers were pulled out from a concentrated solution of cross-linked supramolecular polymers as a result of higher viscosity and lower diffusion coefficients.

Sweet Switch: Sugar-Responsive Bioactive Surfaces Based on Dynamic Covalent Bonding

Smart bioactive surfaces that can modulate interactions with biological systems are of great interest. In this work, a surface with switchable bioactivity in response to sugars has been developed. It is based on dynamic covalent bonding between phenylboronic acid (PBA) and secondary hydroxyls on the "wide" rim of β-cyclodextrin (β-CD). The system reported consists of gold surface modified with PBA-containing polymer brushes and a series of functional β-CD derivatives conjugated to diverse bioactive ligands (CD-X). CD-X molecules are attached to the surface to give specified bioactivity such as capture of a specific protein or killing of attached bacteria. Subsequent treatment with cis-diol containing biomolecules having high affinity for PBA (e.g. fructose) leads to the release of CD-X together with the captured proteins, killed bacteria, and so forth from the surface. The surface bioactivity is thereby "turned off". Effectively, this constitutes an on-off bioactivity switch in a mild and noninvasive way, which has the potential in the design of dynamic bioactive surfaces for biomedical applications.