最新刊期
卷 37 ， 期 1 ， 2017
- 摘要：Polyethylene is the largest-volume synthetic plastic, and its chemical inertness makes it difficult to degrade. Recently, Zheng Huang, Zhibin Guan and coworkers reported a tandem catalytic cross alkane metathesis method for highly efficient degradation of polyethylenes under mild conditions. With the use of widely available, low-value, short alkanes (such as petroleum ethers) as cross metathesis partners, different types of polyethylenes undergo complete conversion into useful liquid fuels and waxes. In addition, the degradation product distribution (liquid fuels versus waxes) can be controlled by the catalyst structure and reaction time.关键词：Plastic;Polyethylene;Cross alkane metathesis;Fuel;Wax
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发布时间：2021-03-12
Research Highlights
- 摘要：Supramolecular polymers are polymeric arrays of monomeric units that held together by highly directional and reversible noncovalent interactions,resulting in polymeric properties in solution and bulk. Due to the dynamic nature of noncovalent interactions,supramolecular polymers display fascinating properties such as reversibility,adaptiveness,self-healing,and stimuli-responsiveness,which are different from their covalent counterparts. These attributes have endowed supramolecular polymers with great potential applications in the field of functional materials,and also have motivated chemists to construct a variety of supramolecular polymers and supramolecular polymeric materials. In conventional supramolecular polymerization,bifunctional covalent monomers should be first synthesized and then supramolecularly polymerized. In contrast,we have proposed a new method for constructing supramolecular polymers by covalent polymerization of supramonomers. Bifunctional supramonomers are first fabricated through noncovalent interactions and then subjected to covalent polymerization. The driving forces for the fabrication of supramonomers are multiple hydrogen bonds,host-guest interactions,and others. This feature article is aimed to summarize the ways for covalent polymerization of supramonomers,including click polymerization and enzyme-triggered condensation of supramonomers based on the host-guest interactions of cucurbit[
8 ]uril and tripeptide Phe-Gly-Gly derivatives,photo-triggered cycloaddition of anthracene end-capped supramonomers driven by pillar[5 ]arene based host-guest interactions,and olefin metathesis polymerization of quadruple hydrogen bonded supramonomers. The advantage of the covalent polymerization of supramonomers is to transfer a not-easy tractable supramolecular polymerization to an easy tractable covalent polymerization. We envision that more noncovalent interactions with higher binding affinity could be used to drive the formation of supramonomers; and more controlled covalent reactions with higher efficiency and milder reaction conditions could be used in the covalent polymerization of supramonomers. By utilizing this method,the controllable fabrication of supramolecular polymers could be realized,which is vital to the study of structure-property relationship of supramolecular polymers,as well as to the design and the construction of functional supramolecular polymers.关键词：Supramonomer;Supramolecular polymer;Covalent polymerization;Self-assembly- 174
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发布时间：2021-03-12 - 摘要：Supramolecular polymer materials, which have emerged as the marriage of polymer science, supramolecular chemistry and materials science, have gained considerable interest in recent years as excellent materials not only due to their properties similar to traditional polymers which are built by covalent bonds, but also because of the reversibility and stimuli-responsiveness of noncovalent bonds. As a result, the reversibility and responsiveness to external stimuli may further provide a range of potential applications, including those as superabsorbers, as matrices in analytical chemistry or biology, and as storage and delivery systems for active substances in the biomedical field. Various kinds of noncovalent interactions can be introduced into polymer materials, such as hydrogen bonding, aromatic stacking interactions, metal coordination, and host-guest interactions. Among them, host-guest interactions have been widely used in the construction of functional supramolecular polymer materials, because they usually combine multiple noncovalent interactions, such as hydrogen bonding, aromatic stacking interactions, charge transfer, and hydrophobic interactions between two complementary compounds, making them not only show good binding affinity, but also form complexes with fixed host-guest geometry and directionality. Moreover, macrocycle-based supramolecular polymer materials can response to abundant external stimuli, such as pH change, photo irradition, anions, cations, temperature, and solvent. Furthermore, macrocycle-based supramolecular polymer materials can be prepared under different conditions, namely in solution, in gel, and in the solid state. Macrocyclic hosts, including crown ethers, cyclodextrins, calixarenes, cucurbiturils, and pillararenes, are the most commonly used building blocks in the fabrication of supramolecular polymer materials. Crown ethers, the first generation of artificial supramolecular hosts, have been utilized to construct various supramolecular polymer materials. Moreover, pillararenes, a kind of novel supramolecular hosts, have shown novel properties and functionalities. In this paper, we stated the utilization of crown ether and pillararene host-guest recognition motifs to control the self-assembly of traditional polymers in order to fabricate supramolecular polymer materials.关键词：Host-Guest recognition motifs;Supramolecular polymer materials;Self-assembly;Crown ethers;Pillararenes
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发布时间：2021-03-12 - 摘要：Porous materials have found extensive applications in, such as, adsorption, separation, catalysis, transport and bio-imaging. In the past two decades, metal-organic frameworks and covalent-organic frameworks have received increasing attention due to their regular pores and large surfaces. Typically, these periodic porous materials are solids that are not soluble or do not decompose upon being dissolved. Since 2013, our lab and several other groups have developed the strategy of self-assembly for constructing water-soluble periodic supramolecular organic frameworks (SOFs) from rationally designed molecular blocks. The most widely used binding motif for the generation of such regular supramolecular architectures involves cucurbit[8]uril (CB[8])-encapsulation-enhanced dimerization of two identical or different aromatic units in aqueous media. By attaching such hydrophobic aromatic units to a rigid triangular, tetrahedral, or octahedral core, tri-, tetra-, or hexa-armed building blocks have been prepared. By mixing these water-soluble precursors with CB[8] in a molar stoichiometry, two-dimensional (2D) honeycomb SOFs, three-dimensional (3D) diamondoid and cubic SOFs have been constructed. From porphyrin-and tetraphenylethene-cored planar tetra-armed precursors, 2D square and rhombic SOFs have also been generated. For the formation of the porphyrin-based 2D SOF and one honeycomb 2D SOF, CB[8]-encapsulation-enhanced donor-acceptor interaction between electron-rich dioxynaphthalene and electron-deficient viologen have been used as the driving force. For another honeycomb 2D SOF, dimerization of viologen radical cations has been used, without or with the encapsulation of CB[8]. The periodicity of both 2D and 3D SOFs has been supported by solution-phase synchrotron X-ray diffraction and scattering experiments. All the SOFs can also maintain the periodicity in their solid state and the pores of the 3D SOFs can be observed using high-resolution TEM. The 2D SOFs have all been revealed to be of monolayer by AFM. All multi-armed building blocks are positively charged and thus both 2D and 3D SOFs may be regarded as a new generation of regular supramolecular polyelectrolytes. One 2D SOF has been found to exhibit antimicrobial activity. The diamondoid 3D SOF exhibits highly efficient capacity of adsorbing anionic organic dye, drug, peptide, nucleic acid and dendrimer guests, while the cubic 3D SOF, the hexa-armed precursor of which contains a Ru(2,2'-bipyridine)32+ core, adsorbs hexaanionic Wells-Dawson-polyoxometallates (POMs). Under the irradiation of visible light (500 nm), the ruthenium complex can sensitize the catalysis of adsorbed POMs in the reduction of proton into hydrogen gas in both homogeneous and heterogeneous manners. The review highlights the advances and, in the last section, provides future directions for new structures and functions.关键词：Supramolecular organic framework;Supramolecular polymers;Porous materials;Self-assembly;Periodicity
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发布时间：2021-03-12 - 摘要：Supramolecular polymer has been the hotspot in the field of supramolecular chemistry,polymer chemistry and material chemistry which has received unprecedented support from a growing number of scientific researchers. Supramolecular polymers are defined as highly directional and ordered polymeric arrays of monomeric units which are brought together by reversible noncovalent interactions including hydrogen bonding,host-guest recognition,donor-acceptor interaction,metal-ligand coordination,and π-π stacking. Photo-responsive functional groups are incorporated into supramolecular polymer systems to obtain photo-responsive supramolecular polymers,which could efficiently combine the unique characteristics of supramolecular polymer and the advantages of photochemical reactions in order to construct novel photochromic materials. Supramolecular polymer chemistry now comprises broad researching areas including main-chain supramolecular polymers and side-chain supramolecular polymers,as well as hierarchical structures. This monograph reviews the recent progress on photo-responsive supramolecular polymers in our group. Specifically,photo-switching between monomer/oligomer and supramolecular polymers constructedvia cyclodextrin,cucurbituril and bis-p-sulfonatocalix[
4 ]arene host recognition were illustrated respectively,together with such various functions as photochromism,aggregation-induced emission,gelation,and so forth. Covalent/noncovalent bond transitions in linear and netlike supramolecular polymers were introduced in details,typically via the photo-induced reversible dimerization reaction of such photo-active groups as coumarin,anthracene,stilbene etc. Photo-responsive reversible morphology transitions of supramolecular polymers realized via photo-responsive reversible chiral morphology transition via cyclodextrin including azobenzene group and those containing chiral binaphthol group in the system,photochrosim and isomerization of the groups in the system. Other functional supramolecular polymers based on the supramolecular interactions in the side chains,like self-healing property realized by the host-guest interaction between the cyclodextrin and bromonaphthalene moieties on their side chains,and cyclodextrin host and hydrogen bonding induced room temperature phosphorescence emission,were also well introduced. Finally,comments and some prospects were given on the future research of the supramolecular polymers as well.关键词：Supramolecular polymer;Photo-responsive;Fluorescence;Room-temperature phosphorescence- 218
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发布时间：2021-03-12
Feature Articles
- 摘要：Supramolecular polymers are polymeric arrays of monomeric units that are held together by highly directional and reversible noncovalent interactions, resulting in polymeric properties in solution and bulk. It is an interdisciplinary direction of polymer science and supramolecular science. In contrast with conventional polymers on the basis of covalent bond, supramolecular polymers have drawn increasing attention because of many fascinating properties such as reversibility, adaptiveness, self-healing, and stimuli-responsiveness owing to the dynamic nature of noncovalent interactions. These attributes have endowed supramolecular polymers with great potential applications in the field of functional materials, and also have motivated chemists to construct a variety of supramolecular polymers and supramolecular polymeric materials. The fabrication of supramolecular polymers and the investigation of functional supramolecular polymers have been a topic of great interest for the scientific communities in China in recent years. This review article is aimed to summarize some research progresses on supramolecular polymers in China, including the design of building blocks and driving forces for the fabrication of supramolecular polymers with high molecular weight, construction of supramolecular polymers with various topologies, new methods for controllable supramolecular polymerization, and functional supramolecular polymers. The characteristics, advantages, and potential applications of supramolecular polymers, as well as the comparisons of the structure and properties between the covalent polymers and the supramolecular polymers are also discussed. Although polymer science on the basis of covalent bond has been and will still be the core science in the polymer community, supramolecular polymers based on noncovalent interactions are complementary to traditional polymer science and represent new growth point by marrying supramolecular science with polymer science. Last but not least, with the aim to push forward the studies on supramolecular polymers, more attention should be paid to developing and enriching supramolecular polymer chemistry and physics, the methods for their characterization and special supramolecular polymers with tailor-made molecular architectures and functions.关键词：Supramolecular polymer;Noncovalent interaction;Supramolecular chemistry;Molecular self-assembly
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发布时间：2021-03-12 - 摘要：As one of the most important soft matters, "supramolecular polymer gel" represents a new concept and more complex gel systems. The construction of these novel supramolecular systems can be based on the hierarchical assembly via different non-covalent interactions. In this case, molecular building blocks can assembly into supramolecular polymers, and then the hierarchical assembly of the corresponding supramolecular polymers can form gels. Actually, the meaning of "supramolecular polymer gels" has been greatly expanded. Thus, although the essential supramolecular polymer gels can be physical gels constructed by self-assembled synthetic polymers, this definition is now more frequently referred to as the gels with supramolecular polymers working as gelators. While these supramolecular polymers can be fabricated based on the self-assembly of low-molecular-weight building blocks, not only covalent polymers. In this context, the building blocks, which are used to form general supramolecular polymer gels, can be covalent polymers, oligomers or small organic molecules. Certainly, building block is only one aspect for understanding "supramolecular polymer gels", the manner of self-assembly is the master key for constructing this type of soft matters. The typical features of "supramolecular polymer gels" can be the complex hierarchical self-assembly of different molecular building blocks within these systems. Whatever covalent polymers or low-molecular-weight organic molecules working as building blocks, much more elaborate molecular packing modes are necessary for the formation of the supramolecular polymer gels. These supramolecular polymer gels have novel nanostructures and properties. For example, some supramolecular polymer gel systems have good dynamic and reversible characteristics with excellent mechanical properties. Although the study on the supramolecular polymer gels has only just begun, it is still attracting more and more interests recently due to their special properties and great application potentials. In this manuscript, we will review the recent research progress in this field. Especially, the construction of the supramolecular polymer gels based on different non-covalent interactions will discussed in details. Moreover, we will also focus on the modulation of their mechanical properties.关键词：Supramolecular polymer gels;Supramolecular polymer;Supramolecular gels;Hierarchical assembly
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发布时间：2021-03-12
Reviews
- 摘要：An AB2-type host-guest-conjugated amphiphilic molecule (Azo-CD2) composed of one azobenzene (Azo) and two β-cyclodextrin (β-CD) units was first synthesized through the click reaction of Azo-(N3)2 intermediate containing two azide groups and mono-6-deoxy-6-alkyne β-CD (β-CD-C≡CH) with one alkynyl group. The molecular structure of Azo-CD2 was confirmed by 1H and 13C nuclear magnetic resonances and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. The morphology transitions of Azo-CD2 self-assemblies were then investigated by transmission electron microscopy (TEM) and dynamic light scattering (DLS). Both TEM and DLS results indicated that Azo-CD2 self-assembled into spherical aggregates without external stimuli, and then transformed to bigger supermolecular hyperbranched polymer self-assemblies (SHPS) induced by ultrasound in aqueous solution. These SHPS could be further dissociated into small branched aggregates under UV light irradiation, whereas reverted to supermolecular hyperbranched self-assemblies again by visible light irradiation. By utilizing the above ultrasound and photo-dually tuned self-assembly morphology transition features, a three-stage programmed drug delivery behavior was observed through the cumulative release curves of doxorubicin (DOX)-loaded self-assemblies. Furthermore, the correlativity between self-assembly morphology transitions and programmed drug release was proved by1H-NMR in D2O and two dimensional nuclear overhauser effect spectroscopy. These results indicated that Azo-CD2 first self-assembled into spherical self-assemblies due to the hydrophilic-hydrophobic interaction, accompanied by a slow release of DOX. And then, the ultrasound stimulus broke the hydrophilic-hydrophobic balance and enhanced the host-guest interaction between β-CD and Azo, further leading to the formation of SHPS with a fast release of DOX. Furthermore, UV light irradiation induced the cis-trans isomerism of Azo and the dissociation of Azo/β-CD, resulting in the dissociation of SHPS into small branched aggregates with a much faster release. While visible light irradiation enhanced the host-guest interaction and made small branched aggregates revert to supermolecular hyperbranched self-assemblies.关键词：Host-guest-conjugated amphiphilic molecule;Supermolecular self-assembly;Supermolecular hyperbranched polymer;Ultrasound-responsiveness;Photo-responsiveness;Programmed drug delivery
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发布时间：2021-03-12 - 摘要：A dipyridyl donor D1 decorated with pillar[5]arene unit and a dipyridyl donorD2 containing neutral guest moiety were successfully synthesized. Through the X-ray single crystal analysis, it was found that the angle between the two pyridine unit in D1 was about 128° and the distance between two nitrogen atoms was about 1.48 nm, while the angle between the two pyridine units of D2 was about 118° and the distance between the two nitrogen atoms was about 0.98 nm, much shorter than that in D1. Thus, a metallacycle containing three pillar[5]arene units (H) and a metallacycle possessing three neutral guest units (G) were successfully constructed in one pot coordination-driven self-assembly from dipyridyl donors (D1 and D2) and 120° di-Pt(II) acceptor through size-control self-sorting strategy. Moreover, driven by the host-guest interaction between metallacycles H and G, a new family of supramolecular polymer, cross-linked by these two kinds of discrete well-defined metllacycles H and G, was gradually constructed with the increase of concentration. By concentration-dependent 1H-NMR measurement, it was found that the typical signals of metllacycle G were gradually disappeared with the increase of concentration, indicating the enhanced host-guest interaction between metallacycles H and G. Meanwhile, the analysis of 2-D diffusion ordered spectroscopy (DOSY) tests of H⊃G showed that the diffusion coefficient D gradually decreased with the increase of concentration, and D1 mmol/L/D16 mmol/L value was ca. 31.6, also demonstrating the formation of supramolecular polymer. Scanning electron microscope (SEM) was also used to investigate the morphology change during the concentration increasing process. More intuitionally, cross-linked networks were observed with the increase of concentration ofH⊃G. Interestingly, the resultant supramolecular polymer could transforme into supramolecular polymer gels when the concentration was increased to a relatively high value (9.9 wt%). Moreover, due to the existence of discrete well-defined metallacycles and the dynamic nature of host-guest hierarchical self-assembly, reversible gel-sol transitions were successfully realized through the disassembly and reassembly of such cross-linked supramolecular polymer networks stimulated by various external stimuli such as temperature, competitive guest, and halide, etc.关键词：Supramolecular polymer gel;Coordination-driven self-assembly;Host-guest interaction;Self-sorting
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发布时间：2021-03-12 - 摘要：Compared to traditional polymers, supramolecular polymers have quite limited structural diversity. In this context, to develop supramolecular polymers with novel backbone structures is highly desired, since this extends not only the diversity of supramolecular polymers, but also might bring in new functions and applications. In this contribution, a rigid rod-like supramolecular monomer, in which electron-deficient viologen units are incorporated at both ends of its skeleton, was designed and synthesized. Its co-assembly with an electron-rich flexible monomer leads to the formation of a rod-coil supramolecular copolymer, driven by cucurbit[8]uril (CB[8])-encapsulation-enhanced donor-acceptor interaction between naphthol segments of the flexible monomer and viologen units of the rigid monomer. The as-prepared supramolecular polymer was systematically characterized by1H-NMR analysis, UV-Vis spectroscopy, diffusion-ordered NMR spectroscopy (DOSY), dynamic light scattering (DLS) and transmission electron microscopy (TEM). While the 1H-NMR result indicated host-guest complexation through the encapsulation of a viologen unit and a naphthol segment in the cavity of one CB[8], the existence of donor-acceptor interaction between the two guest molecules was clearly evidenced by UV-Vis spectrum which exhibited a notable charge-transfer absorption in visible region. The formation of large size supramolecular entities in water was revealed by DOSY and DLS studies. And their linearly polymeric backbones were directly observed by TEM. Based on these experimental results, the polymeric structures of the assembled material were confirmed. Furthermore, DLS and TEM investigations also revealed that the supramolecular polymer adopted an extended linear conformation at low concentration, which further curled into aggregated morphology at high concentration. This might be attributed to the tendency of the supramolecular polymer to decrease its surface energy with increasing concentration. The supramolecular copolymer reported in this paper represents a new type of water-soluble supramolecular polymer. Its concentration-dependent morphology changes are quite interesting, which might shed light on the exploration of unique features and new applications for the supramolecular polymers.关键词：Supramolecular copolymer;CB[8];Donor-acceptor interaction;Rod-coil
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发布时间：2021-03-12 - 摘要：A mono-functionalized pallar[5]arene was designed and synthesized. It was then mixed with AAM, MBA, and AIBN in DMSO. The mixture was stirred at 70℃ for 12 h to give a functionalized polymer of pillar[5]arene. The polymer was then immersed in DMSO and deionized water, respectively, and the polymeric hydrogel was successfully prepared. For the synthesis of the polymer hydrogels with expected morphology and mechanical property, the best molar ratio was found to be 1:9:0.054:0.25 for functionalized pallar[5]arene monomer:AAM:MBA:AIBN was, and the polymerization reaction was at 70℃ for 12 h after the mixture deoxygenized. While the above optimized polymeric hydrogel was immersed in paraquat aqueous solution, a supramolecular polymeric hydrogel was achieved due to the host-guest complexing of paraquat in aqueous soltuion with pillar[5]arene moiety in the hydrogel. And the strong host-guest interaction of pillar[5]arene with paraquat was attributed to charge-transfer interactions between the electron-rich and suitable size of cavities of the pillar[5]arene derivatives and the encircled electron-poor guests. It was found that, during the formaiton of the supramolecular polymeric hydrogel, the color of the hydrogel became deep brown from pale yellow with increasing concentration of paraquat, which provided a good method for the collection and visual detection of paraquat in the aqueous solution by naked eyes. Increasing temperature promoted the absorption of paraquat by the polymeric hydrogel as well. In addition, the detection of paraquat by such polymeric hydrogel was studied by UV-Vis spectroscopy and UV-Vis absorption showed that the concentration of paraquat in water was decreasing because of its absorption by the polymeric hydrogel. This new type of pillararene-based adsorbent materials is considered as a potential adsorbent for the removal of harmful substances from wastewaters.关键词：Supramolecular polymer;Hydrogel;Pallar[5]arene detection;Visual;Herbicide
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发布时间：2021-03-12 - 摘要：Two supramolecular monomers 1 and 2 were first designed and synthesized in order to introduce both metal ligand interaction and host-guest interaction into a same supramolecular system. A cross-linked supramolecular polymer was then formed by hierarchical self-assembly of these two supramolecular monomers, which were further constructed to form a supramolecular polymer gel with multiple stimuli-responsiveness and good self-healing properties. Furthermore, this supramolecular system also showed a strong fluorescence emission in the gel state due to the tetraphenylethene chromophore with aggregation induced emission property in the supramolecular system. As host molecule, monomer 1 as a host molecule was a dibenzo-24-crown-8 (DB24C8) moiety, with two tetraphenylethene fluorescent chromophores in the middle and two terpyridine units at both ends. Monomer 2, as guest molecule, was a bisammonium salt with two dibenzylammonium (DBA) units at both ends. After addition of metal ligand Zn (OTf)2 into monomer 1 solution (V(CHCl3):V(CH3CN)=3:1)), monomer 1 formed a linear supramolecular polymer 3 based on the metal-ligand coordination interactions between terpyridine and Zn (OTf)2. By continuous addition of monomer 2 as cross-linker, the cross-linked supramolecular polymer 4 was obtained based on the host-guest interactions between DB24C8 and dibenzylammonium salt. The formations of the linear and the cross-linked supramolecular polymers were characterized by 1H-NMR, DOSY and viscosity measurement. Furthermore, when the concentration of this cross-linked supramolecular polymer was increased up to 30 mmol/L, a fluorescence supramolecular polymer gel was constructed. The results showed that this fluorescent supramolecular polymer gel had a multiple stimuli-responsiveness (such as temperature, pH, K+ ions and competitive ligand) property, arising from the intrinsic characters of the metal ligand and host-guest interactions. The gel was characterized by fluorescence measurement and photograph method The results also showed that this new fluorescent supramolecular polymer gel was shown to have good self-healing property as confirmed by rheological test.关键词：Supramolecular polymer;Supramolecular polymer gel;Hierarchical self-assembly;Multiple stimuli-responsiveness;Self-healing
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发布时间：2021-03-12 - 摘要：To realize the in situ modulation of self-assembled structure by photo coupling reactions, nanosized clusters were prepared through a covalent grafting of photoactive coumarin and methylcoumarin connecting with triol group onto both sides of a disk-like[MnMo6O19]3- in one-pot reaction, where tetrabutylammonium (TBA) or dioctadecyldimethylammonium (DODA) served as the counterions. The chemical composition and photo polymerization of the obtained hybrids were characterized by elemental analysis, 1H-NMR, FTIR, electrospray ionization-mass spectra (ESI-MS) and single-crystal X-ray diffraction analysis. Because of the synergistic interaction of organic and inorganic components, the hybrid monomers displayed spherical assembly when TBA was acting as the counterion, and flake assembly was observed when DODA served as the counterion of the inorganic cluster. The detailed characterization for the self-assembled structure in the case of DODA indicated the layered sub-structure in organic solution. That is, the organic surfactant component self-assembled into a fully interdigited bilayer with the cationic head locating toward outside of the bilayer while the coumarin grafted inorganic cluster polyanions located between two bilayers. The geometric structure of grafted cluster and spectral measurement revealed a close packing of the photoactive groups. Interestingly, the favorable packing structure made the in situ photoreaction become convenient. Due to the ring coupling occurred in adjacent coumarin groups and the space blocking of polyanionic clusters, the preferred ring addition conformation tended to the linear growth and finally formed polymers in the inner layer of the assembly. Though the present study could not give a strict molecular weight, the coupling degrees were estimated to be in 60%-68%, depending on the organic counterions used. Because of the photo reaction occurring in inner layer, the layered structure was still maintained yet the phase separation between polymerized and non-polymerized domains was observed by transmission electron microscope (TEM). Accompanied by the in situ polymerization, a fluorescence enhancement, ascribed to the coupled coumarin lying in limited space, was found. The present study demonstrated an effective method to construct polyoxometalate based supramolecular polymers in self-assembled systems.关键词：Polyoxometalate;Coumarin;Self-assembly;Photo-controlled dimerization;Structural transformation
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发布时间：2021-03-12 -
Photophysical Properties of Supramolecular Polymeric Nanoparticles with Aggregation-induced Emission
摘要：Tetraphenylethylene functionalized with 2-Ureido-4[1H]-pyrimidinone (TPE-bisUPy), was synthesized and applied to build supramolecular polymers in CHCl3. Nanoparticles of supramolecular polymer from TPE-bisUPy was prepared by using the miniemulsion method with cetyltrimethyl ammonium bromide (CTAB) as surfactant. These nanoparticles were characterized by SEM and DLS, confirming their uniform shape and size. The fluorescence of the nanoparticles significantly enhanced compared with that of TPE-bisUPy in the solution as well as that of the supramolecular polymers in organic solvent. The aggregation of TPE-bisUPy in the supramolecular polymeric nanoparticles leads to such fluorescence enhancement. The size of the nanoparticles was successfully controlled by adjusting the concentration of TPE-bisUPy. Supramolecular polymeric nanoparticles with three different sizes, 46, 66 and 91 nm as determined by DLS, were obtained. The photophysical properties of the supramolecular nanoparticles were tuned by their assembly with Eosin Y (EY). The electrostatic assembly of negatively charged EY on the nanoparticles covered by positively charged surfactant of CTAB facilitated the excitation energy transfer from TPE-bisUPy to EY. The energy transfer efficiency of these three assemblies were 62%, 55% and 39%, respectively. Washed with water, the energy transfer efficiency of these assemblies decreased to 46%, 36% and 33%, respectively. These results indicated that the energy transfer process was dramatically influenced by the electrostatic interaction between the cationic CTAB and the negatively charged EY. The significance of the electrostatic interaction was also confirmed by replacing EY with positively charged Rhodamine 101 as the energy acceptor. Furthermore, the energy transfer was apparent by variation in the emission color of nanoparticles doped with EY upon UV lamp irradiation. The emission color of the assemblies could change from bright blue to bright green and to yellow color by adding different amounts of EY. The energy transfer efficiency was higher when the size of supramolecular nanoparticles was smaller.关键词：Aggregation-induced emission;Supramolecular polymer;Energy transfer;Nanoparticle- 103
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发布时间：2021-03-12 - 摘要：Supramolecular polymers represent a novel class of macromolecules, in which self-assembly serves as a powerful tool and holds the monomeric units together via reversible non-covalent bonds. The ideal non-covalent recognition units should concomitantly fulfill high complexation directionality, strong binding affinity and stimuli-sensitive responsiveness. To meet the requirements, hydrogen bond, metal-ligand and macrocyclic host-guest interactions have been widely served as the non-covalent driving forces for controlled supramolecular polymerization processes. The expansion of novel driving forces and the corresponding recognition motifs are of paramount importance for the current supramolecular polymers researches. In this regard, integration of donor and acceptor chromophores in a mixed supramolecular polymeric array is intriguing, since it is an efficient way to construct nano-sized optoelectronic devices. However, due to the non-specific and non-directional properties of electron donor-acceptor interactions, a variety of erratic stacking modes (such as phase segregation, random or alternating mixing) could potentially exist in the resulting supramolecular polymeric assemblies. Hence, the precise organization of multi-component π-aromatic systems is highly desirable. Our research group has recently developed a "tweezering directed self-assembly" strategy for the construction of well-ordered supramolecular donor-acceptor polymers. As a research extension, herein a novel alkynylplatinum (Ⅱ) terpyridine molecular tweezer/pyrene recognition motif is investigated, which features with intermolecular NH-N hydrogen bond between the amide unit on the guest and the pyridine moiety on the molecular tweezer. Ascribing to the elaborate combination of donor-acceptor and hydrogen-bonding interactions, it demonstrates rather strong binding affinity (Ka=3.58×105 (mol/L)-1). Moreover, by modulating the intermolecular NH-N hydrogen bonds involved in the system, its binding affinity exhibits significantly large variations towards external stimuli. Such non-covalent recognition motifs are further employed as the connecting units for the fabrication of high-molecular-weight supramolecular polymers. Moreover, the resulting polymeric assemblies exhibit interesting dynamic temperature-responsive behaviors, which are promising for the development of adaptive π-functional materials.关键词：Supramolecular polymers;Molecular recognition;Donor-acceptor interactions;Self-assembly;Stimuli-responsiveness
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发布时间：2021-03-12 - 摘要：A heteroditopic host molecule (1) containing a benzo-21-crown-7 and a pillar[5]arene unit was synthesized through the nucleophilic substitution reaction between 4'-chloromethyl benzo-21-crown-7 with monohydroxyl pillar[5]arene using K2CO3 as the base. It is well documented that secondary ammonium salts are suitable guest moieties for 21-crown-7 macrocycle, and pillar[5]arene cavity can strongly bind with neutral guest 5-(1H-1, 2, 3-triazol-1-yl) pentanenitrile (TAPN). Therefore, guest2 containing two TAPN moieties and guest 3 containing two secondary ammonium salt binding sites are chosen as the connectors. Based on orthogonal host-guest interactions of secondary ammonium salt⊂benzo-21-crown-7 and neutral guest⊂pillar[5]arene, a three-component supramolecular polymer of1, 2 and 3 (1:0.5:0.5, molar ratio) was constructed, which was characterized by various techniques such as 1H-NMR, DOSY, viscosity and SEM. In the concentration-dependent 1H-NMR spectra, slow exchange on the NMR timescale was observed for the three-component mixture. At low concentrations, uncomplexed signals of dUC could be obviously found; and at high concentrations, uncomplexed signals were not observed, while the complexed species became very obvious (aC, bC, cC, eC and fC). These results indicated the efficient host-guest interactions in the system. From double-logarithmic curves of specific viscosity (versus monomer concentrations), the slope of the curve in the low concentration region is close to one, suggesting the formation of small oligomers. At high concentrations, the slope value exceeds to 1.53, revealing the formation of supramolecular polymers with large volumn. The critical polymerization concentration (CPC) is 49 mol/L. DOSY further demonstrates the concentration-dependent assembly of supramolecular aggregates. The measured weight average diffusion coefficient decreased dramatically from 3.24×10-10 m2/s to 7.64×10-11 m2/s, as the monomer concentration increased. In addition, long and thin fibers with a diameter of approximately 0.8 μm could easily be drawn from a highly concentrated solution of 1, 2 and 3, providing further direct evidence for the fabrication of high-molecular-weight supramolecular polymer.关键词：Suparmolecular polymer;Self-assembly;Crown ether;Pillararene
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发布时间：2021-03-12 - 摘要：We design a single strand DNA containing two self-complementary sequences and a half i-motif structure. The two self-complementary sequences can self-assemble to form DNA nanowires. Then, the hydrogel can be formed by crosslinking the half i-motif structures under acid condition. The single strand DNA is diluted to 3 mmol/L in 1×TAE buffer (pH=7.5) containing 12.5 mmol/L MgCl2. The system is heated to 95℃ for 5 min and slowly annealed to room temperature. The pH is adjusted to 5.3 to form the DNA hydrogel. The DNA oligomers and assemblies are characterised by PAGE. Then circular dichroism is used to characterize the structure of the duplex and the i-motif. Rheological characterization is used to evaluate the mechanical properties and thermal stability of the hydrogels at different concentration and pH. By changing concentration of the single strand DNA, one can adjust the mechanical strength and thermal stability of the hydrogels. Besides, the mechanical strength can be tuned by changing pH values. When pH value is 5.3, the storage modulus (G') of the hydrogel is 243.9 Pa. When the pH value is increased to 6.0, the G' is lowered to 225.7 Pa because the stability of the i-motif structure decreases as the pH value increases. However, when pH value is changed to 5, the G' is greatly reduced to 57.4 Pa, which is caused by the instability of the duplex structure under acidic condition. In this procedure, the single strand DNA is very easy to be synthesized and the ratio of DNA strands has not to be controlled. Thus, the experimental steps are greatly simplified. Also, the transition of the i-motif between hydrogel formation and its dissociation is reversible and fast (within several seconds), which makes the DNA hydrogel fast pH responsive. Due to these characteristics, this DNA hydrogel holds great potential in bio-sensing, drug delivery and 3D printing.关键词：DNA hydrogel;Self-complementation;I-motif structure;pH responsiveness
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发布时间：2021-03-12
Research Article
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