基于动态化学键构建自愈合高分子水凝胶

高分子水凝胶是一种具有三维网络结构的软材料,能够吸收并保持大量的水分。高分子水凝胶具有良好的生物相容性和力学性能,在生物医学和生物工程领域具有重要的应用价值。自愈合水凝胶是一种能够响应外界刺激并修复自身损伤的智能凝胶。相比传统水凝胶,自愈合水凝胶具有修复损伤的特性,近年来受到科学界的广泛关注。基于动态化学的自愈合水凝胶是一种能够通过动态的共价键或非共价键交联而重新形成三维网络结构从而修复损伤的新型自愈合水凝胶,该水凝胶能够快速多次地修复自身损伤,有良好的环境适应性,为开发多功能智能新材料奠定了基础。本文综述了近年来基于动态化学键构建自愈合水凝胶的研究进展,重点阐述了基于氢键相互作用、金属配位相互作用、主-客体相互作用、离子相互作用、亲疏水相互作用、亚胺键/酰腙键、硼酸酯键和二硫键的自愈合水凝胶的最新研究情况,同时提出了自愈合水凝胶的一些问题,并分析了未来的发展方向。     

Supramolecular Polymers: Rigid Dimers Formed through Strong Interdigitated H‐Bonds Yield Compact 1D Supramolecular Helical Polymers (Small 3/2011)

Hierarchical self‐assembly of small abiotic molecular modules interacting through noncovalent forces is increasingly being used to generate functional structures and materials for electronic, catalytic, and biomedical applications. The greatest control over the geometry in H‐bond supramolecular architectures, especially in H‐bonded supramolecular polymers, can be achieved by using conformationally rigid molecular modules undergoing self‐assembly through strong H‐bonds. Their binding strength depends on the multiplicity of the H‐bonds, the nature of donor/acceptor pairs and their secondary attractive/repulsive interactions. Here a functionalized molecular module is described, which is capable of self‐associating through self‐complementary H‐bonding patterns comprising four strong and two medium‐strength H‐bonds to form dimers. The self‐association of these phenylpyrimidine‐based dimers through directional H‐bonding between two lateral pyridin‐2(1H)‐one units of neighboring molecules allows the formation of highly compact 1D supramolecular polymers by self‐assembly on graphite. A concentration‐dependent study by scanning tunneling microscopy at the solid–liquid interface, corroborated by dispersion‐corrected density functional studies, reveals the controlled generation of either linear supramolecular 2D arrays, or long helical supramolecular polymers with a high shape persistence.     

Supramolecular Chemistry of Carbon-Based Dots Offers Widespread Opportunities

Carbon dots are an emerging class of nanomaterials that has recently attracted considerable attention for applications that span from biomedicine to energy. These photoluminescent carbon nanoparticles are defined by characteristic sizes of <10 nm, a carbon-based core and various functional groups at their surface. Although the surface groups are widely used to establish non-covalent bonds (through electrostatic interactions, coordinative bonds, and hydrogen bonds) with various other (bio)molecules and polymers, the carbonaceous core could also establish non-covalent bonds (π π stacking or hydrophobic interactions) with π-extended or apolar compounds. The surface functional groups, in addition, can be modified by various post-synthetic chemical procedures to fine-tune the supramolecular interactions. Our contribution categorizes and analyzes the interactions that are commonly used to engineer carbon dots-based materials and discusses how they have allowed preparation of functional assemblies and architectures used for sensing, (bio)imaging, therapeutic applications, catalysis, and devices. Using non-covalent interactions as a bottom-up approach to prepare carbon dots-based assemblies and composites can exploit the unique features of supramolecular chemistry, which include adaptability, tunability, and stimuli-responsiveness due to the dynamic nature of the non-covalent interactions. It is expected that focusing on the various supramolecular possibilities will influence the future development of this class of nanomaterials.     

Superamphiphiles as building blocks for supramolecular engineering: towards functional materials and surfaces

Superamphiphiles refer to amphiphiles that are constructed on the basis of noncovalent interactions or dynamic covalent bonds. Superamphiphiles are a new kind of building block for well-defined nanostructured soft materials. This article summarizes different ways to fabricate superamphiphiles, including low-molecular-weight and polymeric superamphiphiles. In addition, the noncovalent nature of superamphiphiles facilitates the incorporation of functional groups, thus opening a new avenue for supramolecular engineering of functional soft materials.     

Supramolecular Soft Material Enabled by Metal Coordination and Hydrogen Bonding: Stretchability,Self-Healing,Impact Resistance, 3D Printing,and Motion Monitoring

Metal coordination can significantly improve the macroscopic performance of many materials by enhancing their dynamic features. In this study, two supramolecular interactions, Fe³⁺–carboxylic acid coordination, and structural water-induced hydrogen bonding, into an artificial polymer were introduced. Various attractive features, including flexibility and stretchability, are achieved because of the bulk state and dynamic hydrogen bonds of poly(thioctic acid-water) (poly[ TA - H ]). These unique features are considerably enhanced after the incorporation of Fe³⁺ cations into poly[ TA - H ] because metal coordination increased the mobility of the poly[ TA - H ] chains. Thus, the poly(thioctic acid-water-metal) (poly[ TA - HM ]) copolymer exhibited better flexibility and stretchability. Moreover, notable underwater/low-temperature self-healing capacity is obtained via the synergistic effect of the metal and hydrogen bonding. Most of the impact energy is quickly absorbed by poly[ TA - H ] or poly[ TA - HM ] and effectively and rapidly dissipated via reversible debonding/bonding via the interactions between the metal and hydrogen. Macroscopic plastic deformation or structural failure is not observed during high-speed (50–70 m s⁻¹) impact experiments or high-altitude (90 m) falling tests. Furthermore, poly[ TA - HM ] displayed good thermal molding properties, which enabled its processing via 3D fused deposition modeling printing. Poly[ TA - HM ] also showed considerable effectiveness for monitoring complicated, dynamic, and irregular biological activities owing to its highly pressure-sensitive nature.     

Extremely Rapid Self-Healable and Recyclable Supramolecular Materials through Planetary Ball Milling and Host–Guest Interactions

The host–guest interaction as noncovalent bonds can make polymeric materials tough and flexible based on the reversibility property, which is a promising approach to extend the lifetime of polymeric materials. Supramolecular materials with cyclodextrin and adamantane are prepared by mixing host polymers and guest polymers by planetary ball milling. The toughness of the supramolecular materials prepared by ball milling is approximately 2 to 5 times higher than that of supramolecular materials prepared by casting, which is the conventional method. The materials maintain their mechanical properties during repeated ball milling treatments. They are also applicable as self-healable bulk materials and coatings, and they retain the transparency of the substrate. Moreover, fractured pieces of the materials can be re-adhered within 10 min. Dynamic mechanical analysis, thermal property measurements, small-angle X-ray scattering, and microscopy observations reveal these behaviors in detail. Scars formed on the coating disappear within a few seconds at 60 °C. At the same time, the coating shows scratch resistance due to its good mechanical properties. The ball milling method mixes the host polymer and guest polymer at the nano level to achieve the self-healing and recycling properties.     

A recyclable supramolecular membrane for size-selective separation of nanoparticles

Most practical materials are held together by covalent bonds, which are irreversible. Materials based on noncovalent interactions can undergo reversible self-assembly, which offers advantages in terms of fabrication, processing and recyclability, but the majority of noncovalent systems are too fragile to be competitive with covalent materials for practical applications, despite significant attempts to develop robust noncovalent arrays. Here, we report nanostructured supramolecular membranes prepared from fibrous assemblies in water. The membranes are robust due to strong hydrophobic interactions, allowing their application in the size-selective separation of both metal and semiconductor nanoparticles. A thin (12 μm) membrane is used for filtration (～5 nm cutoff), and a thicker (45 μm) membrane allows for size-selective chromatography in the sub-5 nm domain. Unlike conventional membranes, our supramolecular membranes can be disassembled using organic solvent, cleaned, reassembled and reused multiple times.     

Coordination‐Driven Hierarchical Assembly of Hybrid Nanostructures Based on 2D Materials

2D materials have received tremendous scientific and engineering interests due to their remarkable properties and broad‐ranging applications such as energy storage and conversion, catalysis, biomedicine, electronics, and so forth. To further enhance their performance and endow them with new functions, 2D materials are proposed to hybridize with other nanostructured building blocks, resulting in hybrid nanostructures with various morphologies and structures. The properties and functions of these hybrid nanostructures depend strongly on the interfacial interactions between 2D materials and other building blocks. Covalent and coordination bonds are two strong interactions that hold high potential in constructing these robust hybrid nanostructures based on 2D materials. However, most 2D materials are chemically inert, posing problems for the covalent assembly with other building blocks. There are usually coordination atoms in most of 2D materials and their derivatives, thus coordination interaction as a strong interfacial interaction has attracted much attention. In this review, recent progress on the coordination‐driven hierarchical assembly based on 2D materials is summarized, focusing on the synthesis approaches, various architectures, and structure–property relationship. Furthermore, insights into the present challenges and future research directions are also presented.     

Design, structure, and properties of functional metal–ligand inorganic modules

From the standpoint of supramolecular chemistry major advances have been made concerning the functional properties of metal–ligand-based coordination complexes/extended solids/polymers. This paper reviews recent results from our laboratories on two contemporary areas of research: (i) spin-crossover Fe^IIN₆ complexes which are representative examples of molecular bistability and (ii) synthesis of tailor-made transition-metal-based 1D coordination polymers and investigation of their magnetic exchange phenomena from the standpoint of molecule-based magnetic materials. Our primary focus is on the magnetic properties which seem to hold promise for future applications. It has been shown that covalent bond-driven discrete complexes/coordination polymers are further stabilized by association due to multiple weak, noncovalent interactions. In the design of Fe^IIN₆ complexes our laboratories have so far relied on synthesis of discrete molecules. However, they are connected by noncovalent interactions, imparting cooperativity.     

自修复聚合物在电化学储能领域的研究进展

自修复聚合物材料能够自行修复在加工和使用过程中产生的微观或者宏观损伤,从而解决材料内部微裂纹难以检测和修复的问题,保持其结构和功能的完整性。将自修复聚合物应用于电化学储能器件中,可有效提升器件的安全可靠性和使用寿命,成为近年来的研究热点之一。本文概括介绍了外援型和本征型自修复聚合物材料的修复机理,着重总结了不需要修复剂、且可实现多次可逆修复的本征型自修复聚合物应用于电化学储能领域的研究进展,以储能器件的电极、电解质以及界面为出发点,综述了自修复功能聚合物分别作为高比能电极黏结剂、界面修饰层、可自修复电解质的研究进展,阐述了自修复机理及其对储能器件电化学性能的影响规律,探讨了自修复聚合物材料在储能领域未来的发展方向。     

A Solvent-Exchange Strategy to Regulate Noncovalent Interactions for Strong and Antiswelling Hydrogels

Physical hydrogels from existing polymers consisting of noncovalent interacting networks are highly desired due to their well-controlled compositions and environmental friendliness; and therefore, applied as adhesives, artificial tissues, and soft machines. Nevertheless, these gels have suffered from weak mechanical strength and low water resistance. Current methodologies used to fabricate these hydrogels mainly involve the freezing–thawing process (cryogels), which are complicated in preparation and short in adjustment of polymer conformation. Here, taking the merits of noncovalent bonds in adjustability and reversibility, a solvent-exchange strategy is developed to construct a class of exogels. Based on the exchange from a good solvent subsequently to a poor one, the intra- and interpolymer interactions are initially suppressed and then recovered, resulting in dissolving and cross-linking to polymers, respectively. Key to this approach is the good solvent, which favors of a stretched polymer conformation to homogenize the network, forming cross-linked hydrogel networks with remarkable stiffness, toughness, antiswelling properties, and thus underwater adhesive performance. The exogels highlight a facile but highly effective strategy of turning the solvent and consequently the noncovalent interactions to achieve the rational design of enhanced hydrogels and hydrogel-based soft materials.     

Extended networks formed by coordination polymers in the solid state

Coordination polymers based upon the self-assembly of metal ions with bridging ligands often show fascinating extended network structures in the solid state. In principle, variation of the molecular components used in the construction of such networks (i.e. metal ion, bridging ligand, co-ligands and counter-anion) affords an almost limitless range of materials that, it is anticipated, will have interesting physical and electronic properties. Thus, linking different metal ions showing different stereochemical preferences with designed bridging-ligands of varying topology and connectivity means that many different network topologies can be accessed. The enormous number of variables associated with coordination network construction means that a ‘combinatorial chemical apporach’ is an appropriate methodology for screening product structures. As it can be difficult to control and predict the nature of the network polymer produced, current research continues to search for an understanding of how building-block design can be used to control extended network structure so that functional materials can be targeted specifically.     

Analyzing the mechanisms of selectivity in biomimetic self-assemblies via IR and NMR spectroscopy of prepolymerization solutions and molecular dynamics simulations

Molecularly imprinted polymers (MIPs) for 2,4-dichlorophenoxyacetic acid were synthesized via a noncovalent approach with 4-vinylpyridine as functional monomer and ethylene glycol dimethacrylate as cross-linker in a methanol/water mixture. Templated polymers synthesized in this self-assembly approach rely on complex formation between the target analyte and functional monomers in porogenic solution prior to radical polymerization. Consequently, the achievable selectivity is governed by the nature and stability of these complexes. The nature of noncovalent interactions responsible for complex formation during imprinting of the template 2,4-dichlorophenoxyacetic acid (2,4-D) with the functional monomer 4-vinylpyridine has been investigated. Fourier transform infrared and 1H NMR spectroscopies provide the fundamental analytical basis for rationalizing the mechanisms of recognition during the imprinting process probing the governing interactions for selective binding site formation at a molecular level. Molecular modeling studies in explicit solvent (chloroform and water) corroborate the importance of hydrogen bonding in aprotic solvents and of hydrophobic interactions in protic media in agreement with the experimental spectroscopic investigations of prepolymerization solutions. Furthermore, chromatographic studies of the synthesized MIPs provided insight on the importance of size, shape, and functionality during selective 2,4-D rebinding processes confirming the results obtained during the prepolymerization studies.     

自修复聚氨酯弹性体的制备及性能研究

目的对自修复聚氨酯弹性体的制备工艺及性能进行综述,为制备高修复效率的聚合物提供指导,并指出其未来的发展趋势。方法从聚氨酯弹性体的修复机理出发,收集并分析自修复聚氨酯弹性体的最新研究进展,总结典型自修复聚氨酯弹性体的制备工艺和性能指标;根据修复机理进行分类,对近年来本征型(Diels-Alder反应、Disulfide键、氢键等)和外援型(微胶囊化)自修复聚氨酯弹性体的制备和性能进行综述,并讨论自修复聚氨酯弹性体的修复效率。结论虽然基于不同动态键的自修复聚氨酯弹性体取得了一定的发展,但开发高修复效率的材料仍然是一个巨大的挑战。总结了提高自修复聚氨酯弹性体力学性能的途径,为实现修复性能与力学性能的平衡提供了指导。     

Functional soft materials from metallopolymers and metallosupramolecular polymers

Synthetic polymers containing metal centres are emerging as an interesting and broad class of easily processable materials with properties and functions that complement those of state-of-the-art organic macromolecular materials. A diverse range of different metal centres can be harnessed to tune macromolecular properties, from transition- and main-group metals to lanthanides. Moreover, the linkages that bind the metal centres can vary almost continuously from strong, essentially covalent bonds that lead to irreversible or 'static' binding of the metal to weak and labile, non-covalent coordination interactions that allow for reversible, 'dynamic' or 'metallosupramolecular', binding. Here we review recent advances and challenges in the field and illustrate developments towards applications as emissive and photovoltaic materials; as optical limiters; in nanoelectronics, information storage, nanopatterning and sensing; as macromolecular catalysts and artificial enzymes; and as stimuli-responsive materials. We focus on materials in which the metal centres provide function; although they can also play a structural role, systems where this is solely their purpose have not been discussed.     

Self-healing coatings in anti-corrosion applications

Nonmetallic (based on polymers or oxides) and metallic protective coatings are used to protect metal products against the harmful action of the corrosion environment. In recent years, self-healing coatings have been the subject of increasing interest. The ability of such coatings to self-repair local damage caused by external factors is a major factor contributing to their attractiveness. Polymer layers, silica-organic layers, conversion layers, metallic layers and ceramic layers, to mention but a few, are used as self-healing coatings. This paper presents the main kinds of self-healing coatings and explains their self-healing mechanisms.     

Rigid dimers formed through strong interdigitated H-bonds yield compact 1D supramolecular helical polymers

Hierarchical self-assembly of small abiotic molecular modules interacting through noncovalent forces is increasingly being used to generate functional structures and materials for electronic, catalytic, and biomedical applications. The greatest control over the geometry in H-bond supramolecular architectures, especially in H-bonded supramolecular polymers, can be achieved by using conformationally rigid molecular modules undergoing self-assembly through strong H-bonds. Their binding strength depends on the multiplicity of the H-bonds, the nature of donor/acceptor pairs and their secondary attractive/repulsive interactions. Here a functionalized molecular module is described, which is capable of self-associating through self-complementary H-bonding patterns comprising four strong and two medium-strength H-bonds to form dimers. The self-association of these phenylpyrimidine-based dimers through directional H-bonding between two lateral pyridin-2(1H)-one units of neighboring molecules allows the formation of highly compact 1D supramolecular polymers by self-assembly on graphite. A concentration-dependent study by scanning tunneling microscopy at the solid-liquid interface, corroborated by dispersion-corrected density functional studies, reveals the controlled generation of either linear supramolecular 2D arrays, or long helical supramolecular polymers with a high shape persistence.     

Chelation Crosslinking of Biodegradable Elastomers

Widely present in nature and in manufactured goods, elastomers are network polymers typically crosslinked by strong covalent bonds. Elastomers crosslinked by weak bonds usually exhibit more plastic deformation. Here, chelation as a mechanism to produce biodegradable elastomers is reported. Polycondensation of sebacic acid, 1,3-propanediol, and a Schiff-base (2-[[(2-hydroxyphenyl) methylene]amino]-1,3-propanediol) forms a block copolymer that binds several biologically relevant metal ions. Chelation offers a unique advantage unseen in conventional elastomer design because one ligand binds multiple metal ions, yielding bonds of different strengths. Therefore, one polymeric ligand coordinated with different metal ions produces elastomers with vastly different characteristics. Mixing different metal ions in one polymer offers another degree of control on material properties. The density of the ligands in the block copolymer further regulates the mechanical properties. Moreover, a murine model reveals that Fe³⁺ crosslinked foam displays higher compatibility with subcutaneous tissues than the widely used biomaterial—polycaprolactone. The implantation sites restore to their normal architecture with little fibrosis upon degradation of the implants. The versatility of chelation-based design has already shown promise in hydrogels and highly stretchy nondegradable polymers. The biodegradable elastomers reported here would enable new materials and new possibilities in biomedicine and beyond.     

Sugar interaction with metals in aqueous solution: indirect determination from infrared and direct determination from nuclear magnetic resonance spectroscopy

In this article, mid-infrared Fourier transform (Mid-FT-IR) and carbon thirteen nuclear magnetic resonance (13C NMR) spectroscopy have been used to determine possible interactions between sucrose and various alkali or alkaline earth metals in aqueous solution. In the presence of these metals, significant shifts in the absorption bands of sucrose were noted by mid-FT-IR coupled with principal component analysis (PCA). These shifts were explained on the basis of weakening of the H-bond network between sucrose and water and possible interactions between sucrose and the metal ion. Factorial maps were established and the spectral patterns obtained show that these interactions vary according to the nature of the metal ion. 13C NMR analysis showed that the carbon atoms of sucrose undergo shielding or deshielding in the presence of metal ions in aqueous solutions. Two factors were invoked to account for the variation of chemical shifts: the rupture of hydrogen bonds due to hydration of the metal ion and the possible coordination of the metal ion to the oxygen atoms of sucrose.     

金属-有机络合聚合物(MOCPs)的研究进展

从配体的角度对中心离子与多齿配体间形成的稳定多孔金属-有机络合聚合物(MOCPs)的发展现状进行了综述.指出该材料自成为研究热点以来,各研究小组在对不同的构件分子进行组合构建新的MOCPs方面富有成效的工作,极大地丰富了络合聚合物的结构数据,但这种材料最引人注目的特性--孔及表面性质的可调控性及其对其各种应用特性,如分子识别、择形催化、择形吸附等所能带来的影响方面的研究还很不够.