A Stretchable Pillararene-Containing Supramolecular Polymeric Material with Self-Healing Property.

Constructing polymeric materials with stretchable and self-healing properties arise increasing interest in the field of tissue engineering, wearable electronics and soft actuators. Herein, a new type of supramolecular cross-linker was constructed through host-guest interaction between pillar[5]arene functionalized acrylate and pyridinium functionalized acrylate, which could form supramolecular polymeric material via photo-polymerization of n-butyl acrylate (BA). Such material exhibited excellent tensile properties, with maximum tensile strength of 3.4 MPa and strain of 3000%, respectively. Moreover, this material can effectively dissipate energy with the energy absorption efficiency of 93%, which could be applied in the field of energy absorbing materials. In addition, the material showed self-healing property after cut and responded to competitive guest.

Gradient Redox-Responsive and Two-Stage Rocket-Mimetic Drug Delivery System for Improved Tumor Accumulation and Safe Chemotherapy.

Recent drug delivery nanosystems for cancer treatment still suffer from the poor tumor accumulation and low therapeutic efficacy due to the complex in vivo biological barriers. To resolve these problems, in this work, a novel gradient redox-responsive and two-stage rocket-mimetic drug nanocarrier is designed and constructed for improved tumor accumulation and safe chemotherapy. The nanocarrier is constructed on the basis of the disulfide-doped organosilica-micellar hybrid nanoparticles and the following dual-functional modification with disulfide-bonded polyethylene glycol (PEG) and amido-bonded polyethylenimine (PEI). First, prolonged circulation duration in the bloodstream is guaranteed due to the shielding of the outer PEG chains. Once the nanocarrier accumulates at the tumoral extracellular microenvironment with low glutathione (GSH) concentrations, the first-stage redox-responsive behavior with the separation of PEG and the exposure of PEI is triggered, leading to the improved tumor accumulation and cellular internalization. Furthermore, with their endocytosis by tumor cells, a high concentration of GSH induces the second-stage redox-responsiveness with the degradation of silsesquioxane framework and the release of the encapsulated drugs. As a result, the rocket-mimetic drug carrier displays longer circulation duration in the bloodstream, higher tumor accumulation capability, and improved antitumor efficacy (which is 2.5 times higher than that with inseparable PEG). It is envisioned that the rocket-mimetic strategy can provide new solutions for improving tumor accumulation and safety of nanocarriers in further cancer chemotherapy.

Synthesis of a Pillar[5]arene-Based Polyrotaxane for Enhancing the Drug Loading Capacity of PCL-Based Supramolecular Amphiphile as an Excellent Drug Delivery Platform.

A pillar[5]arene-based nonionic polyrotaxane (PR) with star-poly(ε-caprolactone) ( S-PCL) as the axle, pillar[5]arene (DEP5) as the wheel and adamantane as the end-capped group is designed and synthesized. The resulting PR is subsequently assembled with ß-cyclodextrin end-capped pH-stimulated poly(acrylic acid) (CD-PAA) via a host-guest interaction to form the supramolecular pseudoblock polymer PR-PAA. This supramolecular pseudoblock polymer could self-assemble in aqueous solution to produce PR-PAA-based supramolecular vesicular nanoparticles (PR-SVNPs), which present significantly enhanced drug loading capacity (DLC, 45.6%) of DOX, much higher than those of superamphiphiles (PCL-PAA, 17.1%). Such a high DLC of PR-SVNPs can be most probably attributed to the greatly decreased crystallinity of PCL in PR. Moreover, the loaded drugs could be selectively released in an acidic microenvironment-responsive manner. Compared to free DOX, the DOX-loaded PR-SVNPs (DOX@PR-SVNPs) shows much enhanced cellular uptake and cytotoxicity against the SMMC-7721. More importantly, thanks to the enhanced permeability and retention (EPR) effect, DOX@PR-SVNPs exhibits appealing features such as extremely low toxicity, highly efficient intratumoral accumulation and substantial antitumor efficacy in vivo.

A Dual-Thermoresponsive Gemini-Type Supra-amphiphilic Macromolecular [3]Pseudorotaxane Based on Pillar[10]arene/Paraquat Cooperative Complexation.

Herein, first we report the preparation of a thermoresponsive [3]pseudorotaxane from cooperative complexation between a water-soluble pillar[10]arene and a paraquat derivative in water. Then we successfully construct the first pillararene-based gemini-type supra-amphiphilic [3]pseudorotaxane from the water-soluble pillar[10]arene and a paraquat-containing poly(N-isopropylacrylamide) based on this new molecular recognition motif in water. This macromolecular [3]pseudorotaxane shows unique dual-thermoresponsiveness. Furthermore, it can self-assemble into polymeric vesicles at 37 °C in water. These vesicles can be further used in the controlled release of small molecules induced by cooling to 25 °C or heating to 60 °C.

Supramolecular polymers with tunable topologies via hierarchical coordination-driven self-assembly and hydrogen bonding interfaces.

A powerful strategy to obtain complex supramolecular materials is the bottom-up construction of noncovalently bound materials by hierarchical self-assembly. This assembly process involves stepwise, uniform increases to the architectural complexity of a substrate, starting from discrete precursors and growing in dimensionality through controlled reactivity to a final product. Herein, two orthogonal processes are exploited: coordination-driven self-assembly and hydrogen bonding. The former relies on the predictable formation of metal-ligand bonds wherein the directionalities of the rigid precursors used determines the structural outcome. The latter uses 2-ureido-4-pyrimidinone interfaces that are structurally robust by virtue of the quadruple hydrogen bonding that can occur between subunits. By combining these two processes into a single system, it is possible to generate hierarchical materials that preserve the attractive tunability associated with discrete supramolecular coordination complexes. For instance, the synthesis of a one-dimensional chain comprising linked metalla-rhomboids is readily adapted to a 2D cross-linked hexagonal network by simply selecting a different metal acceptor precursor as an assembly component. The specific interactions between subunits, in this case platinum(II)-pyridyl bonds and the quadruple H-bonding of ureidopyrimidinone, are unchanged, establishing a unique strategy to obtain supramolecular polymers with marked topological differences with minimal synthetic redesign. In addition, the structural rigidity imposed by the inclusion of the platinum metallacycles serves to minimize the formation of cyclic oligomers, increasing the efficacy of formation and improving the properties of the resultant materials. Furthermore, this study taps the potential of organoplatinum(II) metallacycles in materials science.

Dual-responsive polypseudorotaxanes based on block-selected inclusion between polyethylene-block-poly(ethylene glycol) diblock copolymers and 1,4-diethoxypillar[5]arene.

Based on the selective recognition of the polyethylene (PE) block of polyethylene-block-poly(ethylene glycol) (PE-b-PEG) by 1,4-diethoxypillar[5]arene (DEP5A), two novel thermo and competitive guest (1,4-dibromobutane or hexanedinitrile) responsive polypseudorotaxanes (PPRs) have been successfully constructed. The formation of PPRs both in solution and in the solid state was demonstrated by (1)H NMR, 2D NOESY, and WAXD analyses. TGA data illustrate that PPRs exhibit higher thermal stability than their precursor diblock copolymers. Moreover, intriguing porous disk-like aggregates are produced by electrospraying of PPRs in CHCl3 and the self-assembled structures of PPRs are totally changed by the addition of 1,4-dibromobutane or hexanedinitrile, demonstrating their competitive guest stimuli-responsiveness.

An amphiphilic pillar[5]arene: synthesis, controllable self-assembly in water, and application in calcein release and TNT adsorption.

An amphiphilic pillar[5]arene was made. It could self-assemble to form vesicles and multiwalled microtubes in water. Dynamic light scattering, transmission electron microscopy, scanning electron microscopy, atomic force microscopy, and UV-vis and FTIR spectroscopy were employed to characterize its self-assembly process and the resultant assemblies. The vesicles could encapsulate calcein within their interiors under neutral conditions and release it in response to a decrease in pH. The microtubes, which have primary amine groups on their surfaces, could adsorb TNT through donor-acceptor interactions.

Pillar[6]arene-based photoresponsive host-guest complexation.

The trans form of an azobenzene-containing guest can complex with a pillar[6]arene, while it cannot complex with pillar[5]arenes due to the different cavity sizes of the pillar[6]arene and the pillar[5]arenes. The spontaneous aggregation of its host-guest complex with the pillar[6]arene can be reversibly photocontrolled by irradiation with UV and visible light, leading to a switch between irregular aggregates and vesicle-like aggregates. This new pillar[6]arene-based photoresponsive host-guest recognition motif can work in organic solvents and is a good supplement to the existing widely used cyclodextrin/azobenzene recognition motif.

Self-healing supramolecular gels formed by crown ether based host-guest interactions.

Automatic repair: a polymer with pendent dibenzo[24]crown-8 units (purple in picture) was cross-linked by two bisammonium salts (green) to form two supramolecular gels based on host-guest interactions. These two gels are stimuli-responsive materials that respond to changes of the pH value and are also self-healing materials, as can be seen by eye and as evidenced by rheological data.

Polyacrylic acid-b-polystyrene-passivated CsPbBr3 perovskite quantum dots with high photoluminescence quantum yield for light-emitting diodes.

We report a novel strategy for the preparation of CsPbBr3 perovskite quantum dots by polyacrylic acid-b-polystyrene ligands, which exhibited high stability and photoluminescence quantum yields. The fabricated white light-emitting diodes exhibited luminescence performance with the colour rendering index of 65.5, and a correlated colour temperature of 5464 K.

Biodegradable organosilica magnetic micelles for magnetically targeted MRI and GSH-triggered tumor chemotherapy.

Recently, block copolymer micelles have attracted widespread attention due to their controlled biodegradability and excellent loading capability. Unfortunately, the poor in vivo stability and low delivery efficiency of drug-loaded micelles greatly hampered their biomedical applications. Herein, we develop a new kind of biodegradable magnetite/doxorubicin (Fe3O4/DOX) co-loaded PEGylated organosilica micelles (designated as FDPOMs) with both high circulating stability and smart GSH-triggered biodegradability for magnetically targeted magnetic resonance imaging (MRI) and tumor chemotherapy. The FDPOMs are prepared by the self-assembly of biodegradable polycaprolactone-block-poly(glutamic acid) (PCL-b-PGA), a chemotherapeutic DOX drug and Fe3O4 nanoparticles in an oil/water system, subsequent organosilica cross-linking with 3-mercaptopropyltrimethoxysilane (MPTMS) molecules and surface PEGylation. The resultant FDPOMs exhibit excellent dispersity and stability in biological media, remarkable T2-weighted MR imaging capability, unique GSH-responsive release behavior and selective toxicity to tumor cells. The in vivo experiments show that the FDPOMs not only have improved MR tumor imaging capability, but also exhibit high anti-tumor efficacy due to the strong magnetic targeting ability under an external magnetic field. Consequently, the FDPOMs are promising candidates for magnetically targeted MR imaging and imaging-guided tumor chemotherapy.

Heteroatomic SenS8-n Molecules Confined in Nitrogen-Doped Mesoporous Carbons as Reversible Cathode Materials for High-Performance Lithium Batteries.

A reversible cathode material in an ether-based electrolyte for high-energy lithium batteries was successfully fabricated by homogeneously confining heteroatomic SenS8-n molecules into nitrogen-doped mesoporous carbons (NMCs) via a facile melt-impregnation route. The resultant SenS8-n/NMC composites exhibit highly reversible electrochemical behavior, where selenium sulfides are recovered through the reversible conversion of polysulfoselenide intermediates during discharge-charge cycles. The recovery of selenium sulfide molecules endows the SenS8-n/NMC cathodes with the rational integration of S and Se cathodes. Density functional theory calculations further reveal that heteroatomic selenium sulfide molecules with higher polarizability could bind more strongly with NMCs than homoatomic sulfur molecules, which provides more efficient suppression of the shuttling phenomenon. Therefore, with further assistance of mesopore confinement of the nitrogen-doped carbons, the Se2S6/NMC composite with an optimal Se/S mole ratio of 2/6 presents excellent cycle stability with a high initial Coulombic efficiency of 96.5% and a high reversible capacity of 883 mAh g(-1) after 100 cycles and 780 mAh g(-1) after 200 cycles at 250 mA g(-1). These encouraging results suggest that the heteroatomization of chalcogen (such as S, Se, or Te) molecules in mesostructured carbon hosts is a promising strategy in enhancing the electrochemical performances of chalcogen/carbon-based cathodes for Li batteries.

Melamine-assisted one-pot synthesis of hierarchical nitrogen-doped carbon@MoS2 nanowalled core-shell microspheres and their enhanced Li-storage performances.

A facile and scalable one-pot approach has been developed to synthesize carbon@MoS2 core-shell microspheres by a hydrothermal method, which involves the fast formation of melamine-resorcinol-formaldehyde polymeric microspheres in situ, followed by direct growth of the MoS2 nanowalls on them. The results give unequivocal proof that melamine could be the key to forming the core-shell microspherical morphology, and the contents of MoS2 shells can be easily tuned by initial ratios of the precursors. After a simple heat treatment, the obtained carbon@MoS2 microspheres simultaneously integrate the nitrogen-doped carbon cores and the hierarchical shells which consist of few-layered MoS2 nanowalls with an expanded interlayer spacing. Their unique architectures are favourable for high electronic/ionic conductivity and accommodate volume strain during the electrochemical reaction of the MoS2 anodes in lithium-ion batteries. Thus, a very high reversibility capacity of 771 mA h g(-1) at 100 mA g(-1) after 100 cycles, and a rate capacity of 598 mA h g(-1) at 2000 mA g(-1) could be achieved for the carbon@MoS2 core-shell microspheres with the optimal composition. Furthermore, a thin carbon coating on the carbon@MoS2 microspheres could further increase the reversible capacity to 856 mA h g(-1) after 100 cycles at 100 mA g(-1). These encouraging results suggest that such a facile and efficient protocol can provide a new pathway to produce hierarchical core-shell microspheres which integrate the structural, morphological and compositional design rationales for advanced lithium-ion batteries.

Multifunctional gold nanostar-based nanocomposite: Synthesis and application for noninvasive MR-SERS imaging-guided photothermal ablation.

We report here the design and facile synthesis of multifunctional gold nanostars based nanocomposites (MGSNs) through direct organosilica coating onto anisotropic gold nanostars followed by the conjugation of Gd chelates. The as-synthesized MGSNs possess strong NIR absorbance, SERS signal and enhanced T1-MR imaging capability with excellent dispersivity and uniform size, as well as great photothermal stability and Raman stability under photothermal conditions. Importantly, MGSNs present excellent performance in vivo after their intravenous injection for both MR and SERS imaging and the high efficiency for killing tumor cells through photothermal ablation with NIR irradiation. A combination of the high spatial resolution of MR and the exciting sub-cell-level sensitivity and resolution of SERS can provide comprehensive information about the tumor to achieve the optimized therapeutic outcome. Therefore, MGSNs are of great potential as a multifunctional nanoplatform for MR-SERS bimodal imaging-guided, focused photothermal tumor therapy.

pH-Responsive Supramolecular Control of Polymer Thermoresponsive Behavior by Pillararene-Based Host-Guest Interactions.

We demonstrate precise control of the lower critical solution temperature (LCST) behavior of a thermoresponsive polymer in water by pillararene-based host-guest interactions. The LCST value of the polymer increases upon the stepwise addition of either of the two pillararene hosts. On account of the pH-responsiveness of the pillararene-based host-guest interactions, the recovery of the LCST is achieved by treatment with acid, reflecting the pH-responsive supramolecular control of the LCST.

A multiresponsive, shape-persistent, and elastic supramolecular polymer network gel constructed by orthogonal self-assembly.

A cross-linked supramolecular polymer network gel is designed and prepared, which shows reversible gel-sol transitions induced by changes in pH, temperature, cation concentration, and metal co-ordination. The gel pore size is controlled by the amount of cross-linker added to the system, and the material can be molded into shape-persistent, free-standing objects with elastic behavior. These features are all due to the dynamically reversible host-guest complexation and good mechanical properties of the cross-linked polymer network. No single organogel has previously been reported to possess all of these features, making this supramolecular gel an unprecedentedly intelligent soft material.

Supramolecular polymer nanofibers via electrospinning of a heteroditopic monomer.

Driven by the benzo-21-crown-7/secondary ammonium salt recognition motif, a linear supramolecular polymer was formed from self-organization of a low-molecular-weight self-complementary monomer in chloroform. From this supramolecular polymer, nanofibers were obtained successfully via electrospinning.

New Strategy Targeting Well-Defined Polymethylene-block-Polystyrene Copolymers: The Combination of Living Polymerization of Ylides and Atom Transfer Radical Polymerization.

Well-defined polymethylene-block-polystyrene (PM-b-PS) diblock copolymers were synthesized via a combination of living polymerization of ylides and atom transfer radical polymerization (ATRP) of styrene. A series of hydroxyl-terminated polymethylenes (PM-OHs) with different molecular weight and narrow molecular weight distribution were prepared using living polymerization of ylides following efficient oxidation in a quantitive functionality. Then, the macroinitiators (PM-MIs ($\overline M _{\rm n}$ = 1 900-15 000; PDI = 1.12-1.23)) transformed from PM-OHs in ≈ 100% conversion initiated ATRPs of styrene to construct PM-b-PS copolymers. The GPC traces indicated the successful extension of PS segment ($\overline M _{\rm n}$ of PM-b-PS = 5 000-41 800; PDI = 1.08-1.23). Such copolymers were characterized by (1) H NMR and DSC.