Monitoring cyclodextrin-polyviologen pseudopolyrotaxanes with the Bradford assay

Self-assembled multivalent pseudopolyrotaxanes, composed of lactoside-bearing cyclodextrin (CD) rings threaded on linear polyviologen polymers, have been introduced recently as flexible and dynamic neoglycoconjugates. In the course of this research, it was found that polyviologens are responsive to the Bradford assay, which is traditionally highly selective for proteins. The response of the pseudopolyrotaxanes to the Bradford assay was dependant on, and thus indicative of, the degree of threading of the CD rings onto the polyelectrolyte. The assay was then used to report on the threading and dethreading of native and lactoside-bearing alpha-CD rings onto and off of polyviologen chains, a phenomenon which demonstrates the utility of biochemical assays to address problems unique to supramolecular chemistry.     

葫芦脲与主链聚紫精的超分子自组装制备准聚轮烷及其性质研究

通过葫芦[6]脲(CB[6])与五亚甲基聚紫精(PPeV)在水溶液中于室温下进行超分子组装,得到一种新型的准聚轮烷(PPeVCB),通过¹HNMR、元素分析、IR和X射线粉末衍射(XRD)对其结构进行了表征,证实CB[6]位于PPeV的脂肪链上,并通过非共价键与PPeV结合,且CB[6]与PPeV重复单元的结合摩尔比为1∶1;通过热重分析(TGA)、紫外-可见吸收(UV-Vis)和化学还原等方法对其性质进行了研究,证实了准聚轮烷3比相应的聚合物热稳定性更高、UV-Vis吸收和氧化能力更强.     

Multivalent interactions between lectins and supramolecular complexes: Galectin-1 and self-assembled pseudopolyrotaxanes

Supramolecular chemistry has been employed to develop flexible and adaptable multivalent neoglycoconjugates for binding galectin-1 (Gal-1). Gal-1, a dimeric lectin with two galactoside-binding sites, regulates cancer progression and immune responses. Self-assembled pseudopolyrotaxanes consisting of lactoside-displaying cyclodextrin (LCD) "beads" threaded onto polyviologen "strings" display mobile ligands as a result of cyclodextrin rotation about, and limited translation along, the polymer chain. The pseudopolyrotaxanes rapidly and efficiently precipitate Gal-1 and provide valency-corrected enhancements of up to 30-fold compared to native lactose and 20-fold over free LCD in a T-cell agglutination assay. A supramolecular statistical effect was observed, wherein the efficacy of Gal-1 inhibition correlates with the number of ligands connected to each other solely through mechanical and noncovalent interactions. Such flexible and adaptable self-assembled pseudopolyrotaxanes show promise for the study of multivalent interactions and targeting of therapeutically relevant lectins.     

Formation of a supramolecular gel between alpha-cyclodextrin and free and adsorbed PEO on the surface of colloidal silica: effect of temperature, solvent, and particle size

Aqueous solutions of alpha-cyclodextrin (alpha-CD) complex spontaneously with poly(ethylene oxide) (PEO), forming a supramolecular structure known as pseudopolyrotaxane. We have studied the formation of the complex obtained from the threading of alpha-CD onto PEO, both free in solution and adsorbed on colloidal silica. The kinetics of the reaction were studied by gravimetric methods and determined as a function of temperature and solvent composition for the PEO free in solution. PEO was then adsorbed on the surface of colloidal silica particles, and the monomers were displaced by systematically varying the degree of complexation, the concentration of particles, and the molecular weight of the polymer. The effect of the size of the silica particles on the yield of the reaction was also studied. With the adsorbed PEO, the complexation was found to be partial and to take place from the tails of the polymer. The formation of a gel network containing silica at high degrees of complexation was observed. Small-angle X-ray and neutron scattering experiments were performed to study the configuration of the polymeric chains and confirmed the partial desorption of the polymer from the surface of the silica upon complexation.     

Synthesis of Supramolecular Nanocapsules Based on Threading of Multiple Cyclodextrins over Polymers on Gold Nanoparticles

The CD ' s stuck : Poly(ethylene glycol) chains anchored onto gold nanoparticles (AuNPs) are threaded by multiple α‐cyclodextrin (α‐CD) rings to form a supramolecular outer layer composed of pseudopolyrotaxane columns perpendicular to the nanoparticle surface. Capping the polymer ends confines α‐CD on the nanoparticle surface, cross‐linking the α‐CD rings and then removing the AuNP cores produces supramolecular nanocapsules.

     

Reversible 2D pseudopolyrotaxanes based on cyclodextrins and cucurbit[6]uril

In this paper, a pseudorotaxane (2) was synthesized by reaction of cucurbit [6]uril with 6-[(6-aminohexyl)amino]-6-deoxy-beta-cyclodextrin chloride. Subsequently, pseudorotaxanes 2 were further assembled to form a 2D pseudopolyrotaxane (3) through an alpha,omega-PPG2000 diamino polymer threading the cavities of cyclodextrins in 2, and the resulting pseudopolyrotaxane was comprehensively characterized by FT-IR, NMR, TG-DTA, elemental analysis, and transmission electron microscopy. Significantly, the 2D pseudopolyrotaxane can turn into a main-chain pseudopolyrotaxane in the presence of base, and then the addition of alpha-cyclodextrins may result in a reversible switch between two different 2D pseudopolyrotaxanes.     

Temperature-dependent modulation by biaryl-based monomers of the chain length and morphology of biphenyl-based supramolecular polymers

Supramolecular copolymerizations offer attractive options to introduce structural and functional diversity in supramolecular polymer materials. Yet, general principles and structure–property relationships for rational comonomer design remain lacking. Here, we report on the supramolecular (co)aggregation of a phenylpyridine and bipyridine derivative of a recently reported biphenyl tetracarboxamide-based monomer. We show that both arylpyridines are poor monomers for supramolecular homopolymerizations. However, the two arylpyridines efficiently influence supramolecular polymers of a biphenyl-based polymer. The phenylpyridine derivatives primarily sequestrate biphenyl monomers, while the bipyridine intercalates into the polymers at high temperatures. Thereby, these two poorly homopolymerizing monomers allow for a fine control over the length of the biphenyl-based supramolecular polymers. As such, our results highlight the potential to control the structure and morphology of supramolecular polymers by tailoring the electronic properties of additives.

Supramolecular copolymerizations offer attractive options to introduce structural and functional diversity in supramolecular polymer materials.     

二茂铁基聚合物超分子体系构建和性能的研究进展

二茂铁基聚合物具有独特的氧化还原、电、磁等性能，其构建成超分子体系后在传感器、催化、分子电子学、生物和医学等领域有着广泛的应用前景。本文综述二茂铁基线型聚合物和二茂铁基树枝状聚合物的超分子体系构建和性能方面的研究进展，并对今后的发展方面作一展望。     

Characterization of supramolecular polymers

Supramolecular polymers are made of monomers that are held together by noncovalent interactions. This is the reason for the wide range of novel properties, such as reversibility and responses to stimuli, exhibited by supramolecular polymers. A range of supramolecular polymerization methods have been developed leading to a number of novel supramolecular materials. However, standard techniques for the characterization of supramolecular polymers have yet to be established. The dynamic nature of supramolecular polymers makes them difficult to be fully characterized using conventional polymer techniques. This tutorial review summarizes various methods for characterizing supramolecular polymers, including theoretical estimation, size exclusion chromatography, viscometry, light scattering, vapor pressure osmometry, mass spectrometry, NMR spectroscopy, scanning probe microscopy, electron microscopy, and atomic force microscopy-based single molecule force spectroscopy. Each of these methods has its own particular advantages and disadvantages. Most of the methods are used to characterize the supramolecular polymer chain itself. However, some of the methods can be used to study the self-assembled state formed by supramolecular polymers. The characterization of a supramolecular polymer cannot be realized with a single method; a convincing conclusion relies on the combination of several different techniques.     

Organogelation by polymer organogelators with a L-lysine derivative: formation of a three-dimensional network consisting of supramolecular and conventional polymers

Polymer compounds consisting of a L-lysine derivative and conventional polymers, such as poly(ethylene glycol), polycarbonate, polyesters, and poly(alkylene), have been synthesized and their organogelation properties examined in various solvents. These polymer compounds function as good organogelators that form organogels in many organic solvents and oils. The organogelation ability is almost independent of the polymer backbone. Observation by field-emission scanning electron microscopy (FE-SEM) demonstrates that the polymer organogelators form a supramolecular polymer with a diameter of several tens of nanometers and create a three-dimensional network in organogels. FT-IR spectroscopic analysis shows that the supramolecular polymer is mainly formed by the self-assembly of L-lysine segments through hydrogen-bonding and van der Waals interactions. Furthermore, the organogels formed by the polymer organogelators have a lower gel-sol temperature and higher gel strength than those of a low-molecular-weight model organogelator.     

Self-Assembled Cationic Polypeptide Supramolecular Nanogels for Intracellular DNA Delivery

Supramolecular nanogels are an emerging class of polymer nanocarriers for intracellular delivery, due to their straightforward preparation, biocompatibility, and capability to spontaneously encapsulate biologically active components such as DNA. A completely biodegradable three-component cationic supramolecular nanogel was designed exploiting the multivalent host-guest interaction of cyclodextrin and adamantane attached to a polypeptide backbone. While cyclodextrin was conjugated to linear poly-L-lysine, adamantane was grafted to linear as well as star shaped poly-L-lysine. Size control of nanogels was obtained with the increase in the length of the host and guest polymer. Moreover, smaller nanogels were obtained using the star shaped polymers because of the compact nature of star polymers compared to linear polymers. Nanogels were loaded with anionic model cargoes, pyranine and carboxyfluorescein, and their enzyme responsive release was studied using protease trypsin. Confocal microscopy revealed successful transfection of mammalian HeLa cells and intracellular release of pyranine and plasmid DNA, as quantified using a luciferase assay, showing that supramolecular polypeptide nanogels have significant potential in gene therapy applications.     

A Multiple‐Responsive Self‐Healing Supramolecular Polymer Gel Network Based on Multiple Orthogonal Interactions

Supramolecular polymer networks have attracted considerable attention not only due to their topological importance but also because they can show some fantastic properties such as stimuli‐responsiveness and self‐healing. Although various supramolecular networks are constructed by supramolecular chemists based on different non‐covalent interactions, supramolecular polymer networks based on multiple orthogonal interactions are still rare. Here, a supramolecular polymer network is presented on the basis of the host–guest interactions between dibenzo‐24‐crown‐8 (DB24C8) and dibenzylammonium salts (DBAS), the metal–ligand coordination interactions between terpyridine and Zn(OTf)₂, and between 1,2,3‐triazole and PdCl₂(PhCN)₂. The topology of the networks can be easily tuned from monomer to main‐chain supramolecular polymer and then to the supramolecular networks. This process is well studied by various characterization methods such as ¹H NMR, UV–vis, DOSY, viscosity, and rheological measurements. More importantly, a supramolecular gel is obtained at high concentrations of the supramolecular networks, which demonstrates both stimuli‐responsiveness and self‐healing properties.

     

Synthesis of an Azobenzene-containing Main-chain Crystalline Polymer and Photodeformation Behaviors of Its Supramolecular Hydrogen-bonded Fibers

The synthesis of a new azobenzene(azo)-containing main-chain crystalline polymer with reactive secondary amino groups in its backbone and photodeformation behaviors of its supramolecular hydrogen-bonded fibers are described. This main-chain azo polymer(namely Azo-MP6) was prepared via first the synthesis of a diacrylate-type azo monomer and its subsequent Michael addition copolymerization with trans-1,4-cyclohexanediamine under a mild reaction condition. Azo-MP6 was found to have a linear main-chain chemical structure instead of a branched one, as verified by comparing its ~1H-NMR spectrum with that of the azo polymer prepared via the polymer analogous reaction of AzoMP6 with acetic anhydride. The thermal stability, phase transition behavior, and photoresponsivity of Azo-MP6 were characterized with TGA,DSC, POM, XRD, and UV-Vis spectroscopy. The experimental results revealed that it had good thermal stability, low glass transition temperature,broad crystalline phase temperature range, and highly reversible photoresponsivity. Physically crosslinked supramolecular hydrogen-bonded fibers with good mechanical properties and a high alignment order of azo mesogens were readily fabricated from Azo-MP6 by using the simple melt spinning method, and they could show "reversible" photoinduced bending under the same UV light irradiation and good anti-fatigue properties.     

Supramolecular research by single molecule force spectroscopy

Single molecule force spectroscopy (SMFS) is a new kind of technique based on atomic force microscope, which allows detecting force as low as pico-newtons directly. Herein based on our recent work, we want to demonstrate the investigation of supramolecular structures and interactions in polymer systems by SMFS, such as desorption force between polymer and substrate, identifiability of polymer micelle and its interaction with surfactant, splitting force of ion-induced helical structure in polysaccharide. It shows well that SMFS is a powerful tool in the study of supramolecular science.     

Protein-polymer nanoreactors for medical applications

Major challenges that confront nanoscience in medicine today include the development of efficacious therapies with minimum side effects, diagnostic methods featuring significantly higher sensitivities and selectivities, and personalized diagnostics and therapeutics for theragnostic approaches. With these goals in mind, combining biological molecules and synthetic carriers/templates, such as polymer supramolecular assemblies, represents a very promising strategy. In this critical review, we present protein-polymer systems as reaction spaces at the nano-scale in which the enzymatic reactions take place inside polymer supramolecular assembly, at its interface with the environment or in a combination of both. The location of the protein(s) with respect to the polymer assembly generates a diversity of systems ranging from nanoreactors to active enzymatic polymer surfaces. We describe these both in terms of general modelling and addressing the specific conditions and requirements related to the medical domain. We will particularly present protein-polymer nanoreactors that provide protected spaces for enzymatic reactions. We also show how polymer supramolecular structures, such as micelles, capsules, dendrimers and vesicles, can accommodate sensitive biomolecules to mimic natural systems and functions, and to serve as avenues for new medical approaches. Even though not yet on the market, we will emphasize possible applications of protein-polymer systems that generate reaction nanospaces-as novel ways to advanced medicine (264 references).     

Effectiveness of cell adhesive additives in different supramolecular polymers

Supramolecular motifs in elastomeric biomaterials facilitate the modular incorporation of additives with corresponding motifs. The influence of the elastomeric supramolecular base polymer on the presentation of additives has been sparsely examined, limiting the knowledge of transferability of effective functionalization between polymers. Here it was investigated if the polymer backbone and the additive influence biomaterial modification in two different types of hydrogen bonding supramolecular systems, that is, based on ureido-pyrimidinone or bis-urea units. Two different cell-adhesive additives, that is, catechol or cyclic RGD, were incorporated into different elastomeric polymers, that is, polycaprolactone, priplast or polycarbonate. The additive effectiveness was evaluated with three different cell types. AFM measurements showed modest alterations on nano-scale assembly in ureido-pyrimidinone materials modified with additives. On the contrary, additive addition was highly intrusive in bis-urea materials. Detailed cell adhesive studies revealed additive effectiveness varied between base polymers and the supramolecular platform, with bis-urea materials more potently affecting cell behavior. This research highlights that additive transposition might not always be as evident. Therefore, additive effectiveness requires re-evaluation in supramolecular biomaterials when altering the polymer backbone to suit the biomaterial application.     

Spatiotemporal dynamics of supramolecular polymers by in situ quantitative catalyst-free hydroamination

Implementing chemical reactivity into synthetic supramolecular polymers based on π-conjugated molecules has been of great interest to create functional materials with spatiotemporal dynamic properties. However, the development of an in situ chemical reaction within supramolecular polymers is still in its infancy, because one needs to design optimal π-conjugated monomers having excellent reactivity under mild conditions possibly without byproducts or a catalyst. Herein we report the synthesis of a supramolecular polymer based on ethynyl core-substituted naphthalenediimide (S-NDI2) molecules that react with various amines quantitatively in a nonpolar solvent, without a catalyst, at 298 K. Most interestingly, the in situ reaction of the S-NDI2 supramolecular polymer with a linear aliphatic diamine proceeded much faster than the homogeneous reaction of a monomeric naphthalenediimide with the same diamine, affording diamine-linked S-NDI2 oligomers and polymers. The acceleration of in situ hydroamination was presumably due to rapid intra-supramolecular cross-linking between ethynyl and amino groups fixed in close proximity within the supramolecular polymer. Such intra-supramolecular cross-linking did not occur efficiently with an incompatible diamine. The systematic kinetic studies of in situ catalyst-free hydroamination within supramolecular polymers provide us with a useful, facile and versatile tool kit for designing dynamic supramolecular polymeric materials based on electron-deficient π-conjugated monomers.

A supramolecular polymer based on ethynyl core-substituted naphthalenediimides reacted with various amines quantitatively without a catalyst, exhibiting unconventional reaction kinetics and products.     

Insights into the Correlation of Cross-linking Modes with Mechanical Properties for Dynamic Polymeric Networks

Simultaneously introducing covalent and supramolecular cross-links into one system to construct dually cross-linked networks, has been proved an effective approach to prepare high-performance materials. However, so far, features and advantages of dually cross-linked networks compared with those possessing individual covalent or supramolecular cross-linking points are rarely investigated. Herein, on the basis of comparison between supramolecular polymer network (SPN), covalent polymer network (CPN) and dually cross-linked polymer network (DPN), we reveal that the dual cross-linking strategy can endow the DPN with integrated advantages of CPN and SPN. Benefiting from the energy dissipative ability along with the dissociation of host–guest complexes, the DPN shows excellent toughness and ductility similar to the SPN. Meanwhile, the elasticity of covalent cross-links in the DPN could rise the structural stability to a level comparable to the CPN, exhibiting quick deformation recovery capacity. Moreover, the DPN has the strongest breaking stress and puncture resistance among the three, proving the unique property advantages of dual cross-linking method. These findings gained from our study further deepen the understanding of dynamic polymeric networks and facilitate the preparation of high-performance elastomeric materials.     

Gels Based on Anion Recognition Between Triurea Receptor and Phosphate Anion

Anion recognition between the triurea receptor and phosphate anion is demonstrated as the cross‐linkage to build supramolecular polymer gels for the first time. A novel multi‐block copolymer ( 3) is designed to have functional triurea groups as cross‐linking units along the polymer main chain. By virtue of anion coordination between the triurea receptor and phosphate anion with a binding mode of 2:1, supramolecular polymer gels are then prepared based on anion recognition using 3 as the building block.

     

Molecular Recognition of Immobilized Supramolecular Complex of Ironporphyrin and β-CD Polymer as an Analogue for Peroxidase

The immobilized supramolecular inclusion complex of FeTPPS4 and -CD polymer was applied as a mimesis of peroxidase, and its molecular recognition for twenty substrates was studied. As the space structure;CD interior cavities, high selectivity was obtained by immobilized mimetic enzyme. p-Chlorophenic acid was identified as an optimal substrate in the system tested.