Perspectives on main‐chain hydrogen bonded supramolecular polymers

Supramolecular polymers are assembled from monomeric units held together by reversible non‐covalent interactions. These supramolecular materials display polymeric properties and may soon have important industrial applications. This mini review focuses on the advances in main‐chain supramolecular polymers whose assembly is guided primarily by hydrogen bonding interactions. The design constraints of these new systems discussed include assembly motifs, the strength and directionality of the non‐covalent interactions, association versus reversibility, and environmental effects on the degree of polymerization. Selected literature examples including Meijer's ureidopyrimidinone system are used to highlight the challenges and potential of these supramolecular polymeric materials. Copyright © 2007 Society of Chemical Industry     

Hydrogen‐bonded supramolecular polyurethanes

As a class of materials, supramolecular polymers represent an exciting area of advanced materials research. The combination of unique properties, easy synthesis and response to the environment or external and temporal stimuli makes them important as a focus for the next generation of materials. Understanding and manipulating the non‐covalent interactions leading to polymer assembly allows control over properties by selecting specific building blocks with well‐understood non‐covalent chemistry from an established toolkit. This allows assembly of defined and easily manipulated architectures, where physical characteristics similar to conventional high‐molecular‐weight polymers can be realized. Herein, we describe recent studies of the self‐assembly of polyurethane‐based supramolecular materials. © 2014 Society of Chemical Industry     

Luminescent supramolecular polymers: Cd2+‐directed polymerization and properties

A family of supramolecular polymers was prepared via Cd²⁺‐directed self‐assembly polymerization of bis(2,2′:6′,2″‐terpyridine)‐based ligand monomers, using oligofluorenes and triphenylamine as bridges under mild conditions. The polymers were fully characterized using thermogravimetric analysis, inherent viscosity, electrochemical measurements, UV‐visible spectroscopy, photoluminescence (PL) and electroluminescence (EL). Polymers with oligofluorenes as spacers exhibited blue emission (434–442 nm) in dimethyl acetamide (DMAc) solution, while polymers with triphenylamine as spacer presented an emission peak at 494 nm in DMAc solution. Complexation polymerization of bis(2,2′:6′,2″‐terpyridine)‐based ligand monomers with cadmium(II) improved fluorescence quantum yields dramatically, and the film PL quantum yields of these polymers were about 0.38–0.54. Single‐layer light‐emitting diodes were fabricated with the configuration indium tin oxide (ITO)/polymer/Ca/Al; the EL showed green emission and the onset voltages of the devices were 8–11 V. Copyright © 2006 Society of Chemical Industry     

Metallo‐supramolecular materials based on terpyridine‐functionalized polyhedral silsesquioxane

In this study, novel metallo‐supramolecular materials based on terpyridine‐functionalized polyhedral silsesquioxane were synthesized from 4′‐chloro‐2,2′:6′,2″‐terpyridine and amino‐group‐functionalized polyhedral oligomeric silsesquioxane. The obtained terpyridine‐functionalized polyhedral silsesquioxanes were converted to metallo‐supramolecular hybrid materials by coordination polycondensation reaction with Co(II) or Cu(II) ions. The supramolecular polymers created were characterized by means of structure, morphology and stimuli‐responsive performance employing scanning electron microscopy, amperometric techniques and UV–visible and Fourier transform IR spectroscopy. UV?visible and cyclic voltammetry studies showed that both the optical and electrochemical properties of metallo‐supramolecular materials are affected by the substituent at the pyridine periphery. The supramolecular polymers obtained exhibited electrochromism during the oxidation processes of cyclic voltammogram studies. As a result, these terpyridine‐functionalized polyhedral silsesquioxanes are good candidates for electronic, opto‐electronic and photovoltaic applications as smart stimuli‐responsive materials. © 2013 Society of Chemical Industry     

Double dynamic self‐healing polymers: supramolecular and covalent dynamic polymers based on the bis‐iminocarbohydrazide motif

Self‐healing polymers are a class of functional polymers that, by the virtue of the presence of certain dynamic chemical linkages, may undergo self‐repair at a mechanically cut surface. Herein we report the synthesis of a self‐healing polymer giving access to double dynamicity within the polymer network by making use simultaneously of reversible covalent bonds and dynamic non‐covalent hydrogen bonding interactions. These features are provided, respectively, by doubly dynamic cassettes comprising chemically reversible imine linkages and multiply hydrogen‐bonded urea groups, connected by a siloxane‐based backbone that imparts softness to the material. Such a system can be envisaged to give access to a broad spectrum of functional materials, which can be tuned by convenient modulation of the structural motifs of the polymer. © 2013 Society of Chemical Industry     

超分子聚合物研究进展

介绍了超分子聚合物领域的研究进展及其应用,阐述了其主要类别（如氢键超分子聚合物、配合物型超分子聚合物、π-π堆积超分子聚合物及离子效应超分子聚合物）,最后讨论了超分子化合物研究过程中的表征方法。超分子聚合物的研究前景将朝着更大产率、更简便制备步骤及更新颖结构的方向发展。     

Hydrogen bond‐mediated self‐assembly and supramolecular structures of diblock copolymer mixtures

This review summarizes recent advances in the preparation of hydrogen bonding block copolymer mixtures and the supramolecular structures they form through multiple hydrogen bonding interactions. Hydrogen bonding in block copolymer mixtures that form nanostructures and have unusual electronic, photonic and magnetic properties is a topic of great interest in polymer science. Combining the self‐assembly of block copolymers with supramolecular structures offers unique possibilities to create new materials with tunable and responsive properties. The self‐assembly of structures from diblock copolymer mixtures in the bulk state is readily controlled by varying the weight fraction of the block copolymer mixture and the copolymer composition; in solution, the morphologies are dependent on the copolymer composition, the copolymer concentration, the nature of the common solvent, the amount of the selective solvent and, most importantly, the hydrogen bonding strength. Copyright © 2008 Society of Chemical Industry     

Self‐Assembly of Alkoxy‐Substituted 1,3,5‐Benzenetrisamides Under Controlled Conditions

Supramolecular nanofibers have a great potential to be used as gelating agents, polymer additives, and fibrous material for filtration purposes. To meet the requirements for practical and industrial applications on a large scale, e.g., production of filter media, it is desirable to develop supramolecular systems processable from environmentally friendly water‐based solvent mixtures. Moreover, assessing processing parameters to control the micro‐ and nanofiber diameter is of vital importance. Therefore, an alkoxy‐substituted 1,3,5‐benzenetrisamide, N,N′,N″‐tris(1‐(methoxymethyl)propyl)benzene‐1,3,5‐tricarboxamide is designed that can be self‐assembled into supramolecular nanofibers upon cooling from a water/isopropanol solvent mixture. It is demonstrated that parameters such as stirring velocity and the temperature range during processing allow for a precise adjustment of the cooling profile which in turn enables the control of the supramolecular nanofiber diameters.

     

Self‐healing supramolecular elastomers based on the multi‐hydrogen bonding of low‐molecular polydimethylsiloxanes: Synthesis and characterization

Novel self‐healing supramolecular elastomers based on polydimethylsiloxanes (SESi) were synthesized from a mixture of polydimethylsiloxanes derivers with single, di‐, or tri‐carboxylic acid groups (PDMS–COOH_x, where x = 1, 2, and 3, respectively), diethylene triamine, and urea with a two‐stage procedure. The reactions and the final products were tracked, characterized, and confirmed by Fourier transform infrared spectroscopy, ¹H‐NMR, differential scanning calorimetry, dynamic mechanical analysis, and gel permeation chromatography. Compared with a supramolecular rubber based on dimer acid (reported previously) with a similar synthesis procedure, the SESi showed a lower glass‐transition temperature of about ?113°C for the softer chain of polydimethylsiloxane and showed real rubberlike elastic behavior and self‐healing properties at room temperature or even lower temperatures. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

氢键型超分子聚合物

氢键具有方向性、较强的结合力、动态可逆性以及可预测的识别性能等优点,在超分子聚合物的构筑与性能改善方面有着广泛的应用。本文根据氢键结合位点的数目,系统地综述了主链型、侧链型和结合型氢键超分子聚合物的研究进展;重点阐述了各类氢键结合单元的设计及其在改善聚合物性能中的作用;同时介绍了氢键结合单元在纳米材料、凝胶、液晶等众多领域的应用。在此基础上,展望了未来氢键型超分子聚合物的研究方向,主要包括设计合成能够在生理条件下稳定的多重氢键结合单元以及深化组装机理的研究。     

Thermoreversible supramolecular polyurethanes with self‐complementary quadruple hydrogen‐bonded end groups

In this article, a new type of strongly dimerizing 2‐ureido‐4‐[1H]‐pyrimidinone (UPy) with amine group is synthesized and then used as end‐group to prepare a novel series of supramolecular polyurethanes (PUs). The effects of strong and well‐defined hydrogen bonding on material properties of PUs are studied. In these PUs, the UPy groups consequently serve as thermoreversible associations or the “hard blocks” and the bi‐functional PU chains act as the “monomers.” This theoretical hypothesis is proved by the results of dynamic mechanical thermal analysis (DMTA) and rheological test. Thermal analysis shows that the strong hydrogen bonds from end groups restrict the formation of their microcrystalline domains. The supramolecular PUs exhibit good mechanical performance and their self‐assemble mechanism is discussed. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Naphthoic acid derivatives as hydrogen bond donors in supramolecular materials

The synthesis of a series of 6‐hydroxy‐2‐naphthoic acid derivatives is described. These have been used to form supramolecular main‐chain liquid crystalline polymers. These hydrogen bond donors are complexed with a series of bisfunctionalized rigid pyridine species. These associative chain structures were analyzed through differential scanning calorimetry and polarizing light thermal optical microscopy. The liquid crystalline phases formed displayed mainly enantiotropic nematic phases that display an increase in clearing temperature as the rigid portions of the supramolecular system increased in length. A decrease in the clearing temperature was observed as the length of the flexible spacer group increased. Both of these observations follow established trends in liquid crystalline behavior. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 5890–5894, 2006     

Self‐assembly of rod‐coil molecules into lateral chain‐length‐dependent supramolecular organization

In this article, we report synthesis and characterization of the self‐assembly behavior of coil‐ rod‐coil molecules, consisting of four biphenyls and a p‐terphenyl unit linked together with ether bonds as a rod segment. These molecules contain lateral methyl or ethoxymethyl groups at 2 and 5 positions of the middle benzene ring of p‐terphenyl. The self‐assembling behavior of these materials was investigated by means of DSC, POM, and SAXS in the bulk state. The results reveal that self‐assembling behavior of these molecules is dramatically influenced by a lateral methyl or ethoxymethyl groups in the middle of rod segment. In addition, molecule with PEO (DP = 17) coil chains of identical coil volume fraction to the corresponding molecule connected by PPO (DP = 12) coil chains, shows diverse self‐organizing behavior that may result from the parameters of cross‐sectional area of coil segment and the steric hindrance at the rod/coil interface. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

pH‐/temperature‐sensitive supramolecular micelles based on cyclodextrin polyrotaxane

BACKGROUND: Based on the assembly strategy induced by host‐guest recognition in weak selective solvent, a kind of supramolecular nano‐micelles has been self‐organized from a water‐soluble diblock copolymer, poly(ethylene oxide)‐block‐poly(acrylic acid) (PEO‐b‐PAA), selectively included by ‐cyclodextrins (‐CDs). RESULTS: The spontaneous aggregation of rod‐like ‐CD/PEO‐based pseudo‐polyrotaxanes (pseudo‐PRs) drove the formation of square‐piece in aqueous media and thereafter evolved to spherical assemblies with or without hollow structure as time prolonged, which were stabilized by uncovered hydrophilic PAA segments. Such morphological evolvement attributed to hydrogen bonding between ··CCOOH in PAA and ··COH in ‐CD. However, when alkaline media was used to inhibit hydrogen bonding by ionizing ··CCOOH, the assemblies were only uniform spheres of ca. 100 nm. Meanwhile, the order stacking of PR rods became the basic building units all the time. Herein, the supramolecular PRs contributed to temperature‐response character, namely the formation of assemblies is reversible stimulated with temperature changes. Additionally, the inhibition of deceasing pH to the ionization of free PAA segments made assemblies fuse as microspheres. CONCLUSION: Such pH‐ and temperature‐sensitivity as well as the biocompatibility of components and water as media make a great potential of such nano‐particles as the biomedical materials with controlled‐release function. Copyright © 2007 Society of Chemical Industry     

Electropolymerization of hydrogen bond supramolecular associations between terthiophene‐3‐acetic acid and 4,4′‐bipyridine

Supramolecular assemblies based on 4,4′‐bipyridine as hydrogen acceptor and a terthiophene carboxylic acid (3‐TTAA) as hydrogen donor were synthesized and characterized by Fourier transform IR spectroscopy and DSC. Their electropolymerization was successful in methylene chloride or acetonitrile. The concept of using such supramolecular assemblies in electropolymerization opens the way to the facile synthesis of new π‐conjugated polymers. © 2017 Society of Chemical Industry     

Liquid crystals from star‐like clusto‐supramolecular macromolecules

Supramolecular liquid crystals containing inorganic nanoclusters represent a promising avenue in the field of liquid crystals. The main motivation for developing these hybrid materials originates from the value‐added combination between functional properties of inorganic nano‐objects and the self‐assembly behavior of organic liquid crystal molecules. This review highlights the recent progress regarding nanocluster‐containing supramolecular liquid crystals. Important factors affecting the liquid crystalline behaviors are systematically described and summarized. The driving forces behind the molecular self‐assembly are discussed in depth. Finally, potential applications of the liquid‐crystalline nanohybrids are discussed. © 2014 Society of Chemical Industry     

A Self‐Healing PAM/CMHPG System for Unconventional Reservoir Stimulation

A hybrid chemically and physically linked polyacrylamide (PAM)/carboxymethyl hydroxypropyl guar gum (CMHPG) system is prepared via a fast and controllable one‐pot strategy. Due to the synergetic effect of the non‐covalent interactions between chains, these systems show improved, balanced mechanical properties. The apparent morphology, storage modulus G′, and loss modulus G″ show that these systems have rapid and almost full recovery ability (the self‐healing efficiency can reach 95%) with several hydrogen‐bonding interactions between two networks. This self‐healing property can cover the shortage of G′, G″, and viscosity loss at high shear force, which will help the system keep enough viscosity to create fractures or carry proppants during the whole fracturing process. Meanwhile, the self‐healing fracturing fluid can be broken easily and flow back to surface with little damage to the fracture conductivity, indicating great potential in unconventional reservoir which is sensitive to the fracturing fluid damage.     

Aliphatic polycarbonate‐based polyurethane elastomers and nanocomposites. I. The influence of hard‐segment content and macrodiol‐constitution on bottom‐up self‐assembly

Aliphatic polycarbonate‐based polyurethane (PC‐PU) elastomers as well as their nanocomposites with organic‐modified clay (bentonite for organic system) were synthesized. Macrodiols (MD) (randomly copolymerized aliphatic PC‐glycols of molecular weight of about 2000: T5652, T4672, and T4692), hexamethylene diisocyanate, and butane‐1,4‐diol were used as starting materials. Solid‐state NMR and Fourier transform infrared spectroscopy, small‐angle X‐ray scattering, wide‐angle X‐ray diffraction, atomic force microscopy, and transmission electron microscopy were used for studying the bottom‐up self‐assembly of building units from the segmental level up that of organized structures of micrometer sizes. Contents of hard segments formed by the reaction of chain extender with diisocyanate plays a dominant role for the degree of ordering and related phenomena, while the MD chain has only limited effect on PC‐PU properties. The spectroscopy and scattering experiments suggest that bentonite particles incorporate well in the structure and promote the ordering of hard segment domains in PC‐PU matrix as compared with the nanofiller‐free analogue. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

‘Bricks and mortar’ nanoparticle self‐assembly using polymers

Developments in self‐assembly methods allow access to hierarchical materials featuring a wide range of functionality and applications. Polymer‐based self‐assembly of nanoparticles opens up new avenues for the fabrication of highly structured nanocomposites that can serve as bridges between ‘bottom‐up’ and ‘top‐down’ methods. Of various interactions leading to self‐assembly of nanocomposites, hydrogen bonding and electrostatic interactions are commonly utilized. In this review, we illustrate the design and subsequent property tuning of various self‐assembled nanocomposite materials that were developed based on these interactions. Copyright © 2007 Society of Chemical Industry     

Side‐chain liquid‐crystalline polymers with a limonene‐co‐methyl methacrylate main chain: Synthesis and characterization of polymers with phenyl benzoate mesogenic groups

A new series of liquid‐crystalline polymers with a polymer backbone of limonene‐co‐methyl methacrylate were synthesized and characterized, and the spacer length was taken to be nine methylene units. The chemical structures of the obtained olefinic compound and polymers were confirmed with elemental analysis and proton nuclear magnetic resonance spectroscopy. The thermal behavior and liquid crystallinity of the polymers were characterized with differential scanning calorimetry and polarized optical microscopy. The polymers exhibited thermotropic liquid‐crystalline behavior and displayed a glass‐transition temperature at 48°C. The appearance of the characteristic schlieren texture confirmed the presence of a nematic phase, which was observed under polarized optical microscopy. These liquid‐crystalline polymers exhibited optical activity. A comparison was also made with polyacrylates and polymethacrylate‐based materials. This revealed that the nature of the polymer backbone had a major effect on the liquid‐crystalline properties. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4595–4600, 2006