Advanced supramolecular polymers constructed by orthogonal self-assembly

Large aggregates, constructed by linking together monomer building blocks via non-covalent interactions with polymer properties, are regarded as supramolecular polymers. Many kinds of non-covalent interactions, such as metal-ligand coordination, hydrogen bonding, π-π stacking, ionic interaction, and host-guest interaction etc., can be involved in the binding interactions of monomer building blocks, as well as in the modification of the side chain for the construction of variable supramolecular polymers. In this tutorial review, we summarized the reported supramolecular polymers fully- or partially-created from the combination of multiple non-covalent binding interactions, mainly of two kinds, in the orthogonal way.     

Near-Infrared-Emissive Self-assembled Polymers <Emphasis Type="Italic">via</Emphasis> the Implementation of Molecular Tweezer/Guest Complexation on a Supramolecular Coordination Complex Platform

Coordination-driven self-assembly strategy has demonstrated the efficiency and versatility to construct well-ordered supramolecular coordination complexes (SCCs) such as discrete metallacycles and metallacages.In recent years,it has aroused tremendous interest to build more complexed self-assembled structures via the implementation of additional non-covalent recognition motifs on the SCCs platform.In this work,we have successfully attained this objective,with the elaborate manipulation of non-interfering pyridine-Pt2+and molecular tweezer/guest complexation in a hierarchical self-assembly manner.The resulting SCCs-based linear supramolecular polymers exhibit intriguing NIR-emissive behaviors,primarily attributed to the presence of intermolecular Pt(Ⅱ)-Pt(Ⅱ) metal-metal interactions in the non-covalent tweezering structure.Hence,supramolecular engineering of multiple non-covalent interactions offers a feasible avenue toward functional materials with tailored properties.     

超分子聚合机理

与共价键聚合物由单体(M1)通过共价键连接不同,超分子聚合物是由单体(M2)通过非共价键连接而成的长链大分子。聚合包括分子聚合和超分子聚合。超分子聚合描述M2通过非共价键自组装形成超分子聚合物的过程,涉及氢键、π-π堆砌型和立体匹配等驱动力以及分子识别、协同性等特征,与M1通过共价键形成聚合物的过程(分子聚合)不同。为了理解超分子聚合物链结构形成机理,本文分析和讨论超分子聚合的三个主要机理:(1)线性链生长;(2)螺旋链生长;(3)拓扑链生长。     

从超分子聚合物到超分子有机框架:组装溶液相超分子结构的周期性

单体分子在溶液相自发形成周期性的网络结构,是超分子化学和分子自组装研究领域的重大挑战.多头基分子在溶液相通过分子间非共价键作用可以形成超分子聚合物.提高多头基(三头基和四头基)分子骨架的刚性,可以提高结合位点的结构预组织,进而增强分子间相互作用的协同性和多价性特征,提高自组装结构的有序性或周期性.本文综述了多头基分子自组装形成超分子聚合物的一些重要进展,介绍了二维超分子有机框架(一类新的溶液相周期性自组装网络结构研究的最新进展.     

Self‐Healing Polymers via Supramolecular Forces

As polymers and polymeric materials are “the” smart invention and technological driving force of the 20th century, the quest for self‐healing or self‐repairing polymers is strong. The concept of supramolecular self‐healing materials relies on the use of noncovalent, transient bonds to generate networks, which are able to heal the damaged site, putting aspects of reversibility and dynamics of a network as crucial factors for the understanding and design of such self‐healing materials. This Review describes recent examples and concepts of supramolecular polymers based on hydrogen bonding, π–π interactions, ionomers, and coordinative bonds, thus convincingly discussing the advantages and versatility of these supramolecular forces for the design and realization of self‐healing polymers.     

Supramolecular Porphyrin Copolymer Assembled through Host–Guest Interactions and Metal–Ligand Coordination

Bisporphyrin cleft molecule 1 Zn possessing a guest moiety assembled to form supramolecular polymers through host–guest interactions. Bispyridine cross‐linkers created interchain connections among the supramolecular polymers to form networked polymers in solution. Solution viscometry confirmed that the cross‐linked supramolecular polymers were highly entangled. Frequency‐dependent linear viscoelastic spectroscopy revealed that the supramolecular polymers generated well‐entangled solutions with associating and networking polymers, whereas the solid‐like aggregates moved individually without breaking and reforming structures below the transition temperature of 9.6 °C. Morphological transition of the supramolecular polymers was evidenced by AFM images; the non‐cross‐linked polymer resulted in wide‐spread thin networks, while the cross‐linked networks produced thicker worm‐like nanostructures. The supramolecular networks gelled in 1,1,2,2‐tetrachloroethane, and an elastic free‐standing film was fabricated with a Young’s modulus of 1 GPa.     

Supramolecular polymeric hydrogels

The supramolecular crosslinking of polymer chains in water by specific, directional and dynamic non-covalent interactions has led to the development of novel supramolecular polymeric hydrogels. These aqueous polymeric networks constitute an interesting class of soft materials exhibiting attractive properties such as stimuli-responsiveness and self-healing arising from their dynamic behaviour and that are crucial for a wide variety of emerging applications. We present here a critical review summarising the formation of dynamic polymeric networks through specific non-covalent interactions, with a particular emphasis on those systems based on host-guest complex formation, as well as the characterisation of their physical characteristics. Aqueous supramolecular chemistry has unlocked a versatile toolbox for the design and fine-tuning of the material properties of these hydrogels (264 references).     

Supramolecular Polymerization Driven by the Dimerization of Single-stranded Helix to Double-stranded Helix

We reported a type of strong and highly directional non-covalent interactions based on the dimerization of single-stranded helix to double-stranded helix that can achieve supramolecular polymerization,giving rise to the formation of linear supramolecular polymers.     

Perfluorocarbon-hydrocarbons self-assembly: halogen bonding mediated intermolecular recognition

Halogen bonding is discussed as an interaction that is capable of overcoming the reluctance shown by fluorinated compounds towards interactions with hydrocarbons. This non-covalent interaction is sufficiently strong to enact formation of supramolecular architectures where perfluorocarbons, hydrocarbons, and inorganic salts are self-assembled. Examples are discussed which exemplify the consistency and versatility of this interaction in affording numerous and structurally different hybrid materials. The importance of fluorine in determining the overall packing of the formed architectures is also highlighted.     

Modulating the properties of quadruple hydrogen bonded supramolecular polymers by photo-cross-linking between the coumarin moieties

Novel linear supramolecular polymers were successfully constructed by self-assemblies of coumarin-bridged bifunctional UPy derivative.Benefitting from the photodimerization ability of the coumarin moieties,the linear supramolecular polymers could form the large three-dimensional polymer networks upon UV light irradiation via photo-cross-linking,which provides a viable and alternative procedure to modulate the properties of supramolecular polymers.     

Supramolecular perspectives in colloid science

Supramolecular chemistry puts emphasis on molecular assemblies held together by non-covalent bonds. As such, it is very close in spirit to colloid science which also focuses on objects which are small, but beyond the molecular scale, and for which other forces than covalent bonds are crucial. We discuss in this review the preparation and properties of new colloidal systems which borrow on the one hand from classical topics in colloid science, such as micellization, and on the other hand from concepts in supramolecular chemistry, such as reversible supramolecular polymers.     

Asymmetrical supramolecular interactions as basis for complex responsive macromolecular architectures

Intrigued by natural responsive systems based on a combination of macromolecules and non-covalent interactions, polymer scientists have mimicked such systems by the formation of supramolecular polymers based on ionic interaction, hydrogen bonding and metal coordination. In recent years, the focus has shifted from rather simple non-directional and self-complementary interactions to the use of asymmetrical directional supramolecular interactions that allow the formation of complex responsive macromolecular architectures such as block copolymers, star-shaped polymers and graft copolymers. This feature article covers these recent developments on the use of asymmetrical supramolecular interactions in polymer science. Special attention is given to the formation of complex macromolecular architectures using directional supramolecular interactions. In addition, the responsiveness of the resulting macromolecular systems is discussed based on the assembly and/or disassembly that can be triggered by changes in external conditions.     

二-2,2′:6′,2″-三联吡啶-4′-(4-苯甲酰)-乙二胺的合成

二、三联吡啶作为螯合配体可以和过渡金属离子生成高度稳定的配合物,并具有有趣的物理性质。因此在过去的几十年里,二、三联吡啶金属配合物受到广泛而深入的研究。文章在前人的研究基础上获得了含官能化双(三联吡啶)单元结构的二-2,2′:6′,2″-三联吡啶-4′-(4-苯甲酰)-乙二胺配体,可以作为非共价聚合物的很有效的构建模块,合成有趣的金属超分子聚合物。     

Supramolecular polymerization of oligopyrenotides--control by single, natural nucleotides

Amphiphilic heptapyrenotides (Py(7)) assemble into supramolecular polymers. Here we present a comprehensive spectroscopic study of aggregates and co-aggregates of the non-chiral Py(7) and its mono- or di-substituted nucleotide analogs (Py(7)-N and N-Py(7)-N'). The data show that the formation of supramolecular polymers from oligopyrenotides is highly sensitive to the nature of the attached, chiral auxiliary. A single natural nucleotide may be sufficient for the fine tuning of the aggregates' properties by changing the mechanism of aggregation from an isodesmic to a nucleation-elongation process, which results in a high degree of amplification of chirality in the formed supramolecular polymers. Watson-Crick complementarity does not play a significant role, since co-aggregates of oligomers modified with complementary nucleotides show no signs of supramolecular polymerization. Depending on the nucleotide, the helical sense of the polymers is shifted to an M-helix or a P-helix. The findings demonstrate the value of oligopyrenotides as oligomeric building blocks for the generation of optically active supramolecular polymers.     

Physical organic chemistry of supramolecular polymers

Unlike the case of traditional covalent polymers, the entanglements that determine properties of supramolecular polymers are defined by very specific, intermolecular interactions. Recent work using modular molecular platforms to probe the mechanisms underlying mechanical response of supramolecular polymers is reviewed. The contributions of supramolecular kinetics, thermodynamics, and conformational flexibility to supramolecular polymer properties in solutions of discrete polymers, in networks, and at interfaces, are described. Molecule-to-material relationships are established through methods reminiscent of classic physical organic chemistry.     

A polysaccharide/tetraphenylethylene-mediated blue-light emissive and injectable supramolecular hydrogel

A luminescent and injectable supramolecular hydrogel was successfully constructed through the non-covalent cross-linking of polymers mediated by tetraphenylethylene-bridged cyclodextrin oligomers, presenting the strong blue fluorescence, the reversible gelation behavior responsive to various external stimuli and the good mechanical property of shear thinning.     

Two-Dimensional Supramolecular Polymerization of a Bis-Urea Macrocycle into a Brick-Like Hydrogen-Bonded Network

We report on a dendronized bis-urea macrocycle 1 self-assembling via a cooperative mechanism into two-dimensional (2D) nanosheets formed solely by alternated urea-urea hydrogen bonding interactions. The pure macrocycle self-assembles in bulk into one-dimensional liquid-crystalline columnar phases. In contrast, its self-assembly mode drastically changes in CHCl₃ or tetrachloroethane, leading to 2D hydrogen-bonded networks. Theoretical calculations, complemented by previously reported crystalline structures, indicate that the 2D assembly is formed by a brick-like hydrogen bonding pattern between bis-urea macrocycles. This assembly is promoted by the swelling of the trisdodecyloxyphenyl groups upon solvation, which frustrates, due to steric effects, the formation of the thermodynamically more stable columnar macrocycle stacks. This work proposes a new design strategy to access 2D supramolecular polymers by means of a single non-covalent interaction motif, which is of great interest for materials development.     

Depolymerization of supramolecular polymers by a covalent reaction; transforming an intercalator into a sequestrator

Controlling the reciprocity between chemical reactivity and supramolecular structure is a topic of great interest in the emergence of molecular complexity. In this work, we investigate the effect of a covalent reaction as a trigger to depolymerize a supramolecular assembly. We focus on the impact of an in situ thiol–ene reaction on the (co)polymerization of three derivatives of benzene-1,3,5-tricarboxamide (BTA) monomers functionalized with cysteine, hexylcysteine, and alkyl side chains: Cys-BTA, HexCys-BTA, and a-BTA. Long supramolecular polymers of Cys-BTA can be depolymerized into short dimeric aggregates of HexCys-BTAvia the in situ thiol–ene reaction. Analysis of the system by time-resolved spectroscopy and light scattering unravels the fast dynamicity of the structures and the mechanism of depolymerization. Moreover, by intercalating the reactive Cys-BTA monomer into an unreactive inert polymer, the in situ thiol–ene reaction transforms the intercalator into a sequestrator and induces the depolymerization of the unreactive polymer. This work shows that the implementation of reactivity into supramolecular assemblies enables temporal control of depolymerization processes, which can bring us one step closer to understanding the interplay between non-covalent and covalent chemistry.

We report on the controlled depolymerization of supramolecular 1D polymers into well-defined dimers triggered by a covalent reaction on the side chains of the monomer.     

Supramolecular nanoribbons and nanoropes generated from hydrogen-bonded supramolecular polymers containing perylene bisimide chromophores

A perylene bisimide anchored with melamine hydrogen-bonding units has been prepared, and its supramolecular polymerization upon binding with N-dodecylcyanurate (CA) was examined. The resulting flexible supramolecular polymers self-organized via a pi-pi stacking interaction between perylene chromophores, affording ribbonlike aggregates in cyclic alkanes and ropelike aggregates in acyclic alkanes to form gels. [structure: see text]