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     

Side‐chain functionalized supramolecular polymers

Over the past two decades, the field of supramolecular polymer chemistry has developed from a curiosity to a mature area of polymer science. Among the most promising subjects in this large field are noncovalently functionalized side‐chain polymers that have been investigated extensively as a result of their modular character and ease of synthesis. Side‐chain functionalized polymers have the potential for a profound impact on complex materials. For example, for side‐chain functionalized polymers based on a single noncovalent interaction, materials for a variety of applications ranging from liquid crystalline and electro‐optical materials to drug delivery systems have been reported. Furthermore, materials based on this novel methodology may overcome several shortcomings of current covalent multifunctionalization strategies such as highly complex materials that are extremely difficult or impossible to fabricate with current methods. In this review, basic design requirements, advantages and potential applications are presented. Copyright © 2006 Society of Chemical Industry     

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 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.

     

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     

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     

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     

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     

Multiscale approach to the morphology,structure, and segmental dynamics of complex degradable aliphatic polyurethanes

A multiscale approach spanning from the segmental (subnanometer) up to micrometer level was applied for detailed study of the self‐assembly of aliphatic block polyurethane (PU) elastomers. To understand the principles of the self‐organization of hard and soft segments in the complex multi‐component systems, several two‐component model PU samples, that is, the products of 1,6‐diisocyanatohexane (HDI) with three diols differing in the length and constitution were also prepared, characterized, and investigated: (i) polycarbonate‐based macrodiol (MD), (ii) biodegradable oligomeric diol (DL‐L; product of butane‐1,4‐diol and D,L‐lactide), and (iii) butane‐1,4‐diol (BD). The study (particularly ¹³C‐¹H PILGRIM NMR spectra) reveals complex internal organization and interesting (application appealing) behavior of multi‐component PUs. Hard segments (HDI+BD products) feature self‐assembled and significantly folded chain conformations with interdomain spacing 15–22 nm (small‐angle X‐ray scattering analysis). The small domains are hierarchically assembled in various structural formations of µm size (spherulites) depending on PU composition, as detected by transmission electron microscopy and atomic force microscopy. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41590.     

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.     

Self‐assembling metal coatings from phosphated and siloxane‐modified polyurethane dispersions: An analysis of the coating–air interface

Polyurethane dispersion coatings containing phosphate and siloxane chains were evaluated for their self‐assembling properties for a single‐coating system. Dynamic contact angles (DCAs) and X‐ray photoelectron spectroscopy (XPS) were used to study the coating–air interface. The siloxane chains were the predominant species on the surfaces of the coatings. The wetting properties of the coating–air interface were reversed when the coated panels were immersed in an ionic solution, and the decrease in hydrophobicity was linear with time. Results from XPS and DCA analyses were similar. The self‐assembling properties of the coatings could be useful in the development of hydrophobic coatings from hydrophilic polymers. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 893–899, 2003     

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     

Engineering hydrogen‐bonded duplexes

Based on several simple, readily available building blocks, oligoamide strands carrying various arrays of hydrogen‐bond donors and acceptors, i.e. hydrogen‐bonding sequences, have been designed and synthesized. Detailed characterization indicates that these oligoamide strands associate via their hydrogen‐bonding edges into doubled stranded pairs (duplexes), which are characterized by programmable sequence specificity and adjustable stability. Using these hydrogen‐bonded duplexes as association units, supramolecular structures, such as β‐sheets and non‐covalent block copolymers, are obtained by simply mixing the corresponding components. Recently, by incorporating reversible covalent interactions into these hydrogen‐bonded duplexes, sequence‐specific formation of covalently linked structures has been realized under thermodynamic conditions, which has opened an entirely new avenue to the development of previously unknown dynamic covalent structures such as various block copolymers. Copyright © 2007 Society of Chemical Industry     

Synthesis and self‐assembly of hyperbranched polyethers peripherally modified with adenosine 5′‐monophosphate

The chloride functionalized hyperbranched poly(3‐ethyl‐3‐oxetanemethanol) (HBPO) was prepared via reaction of thionyl chloride with hydroxyl groups. Adenosine 5′‐monophosphate (AMP) groups were attached to HBPO in CH₂Cl₂ in the presence of triethylamine (TEA) as an acceptor of HCl. The self‐assembly of resultant hyperbranched molecules bearing self‐complementary hydrogen‐bonding patterns would allow the generation of a highly organized supramolecular architecture in a selected solvent. The morphologies of self‐assembly structures were depended on the level of AMP in polymer and the concentration in solvent. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1147–1152, 2006