Self‐Healing Supramolecular Materials Constructed by Copolymerization via Molecular Recognition of Cavitand‐Based Coordination Capsules

The repeating guest units of poly‐(R)‐ 2 were selectively encapsulated by the self‐assembled capsule poly‐ 1 possessing eight polymer side chains to form the supramolecular graft polymer (poly‐ 1 )_n?poly‐(R)‐ 2 . The encapsulation of the guest units was confirmed by ¹H NMR spectroscopy and the DOSY technique. The hydrodynamic radius of the graft polymer structure was greatly increased upon the complexation of poly‐ 1 . The supramolecular graft polymer (poly‐ 1 )_n?poly‐(R)‐ 2 was stably formed in the 1:1 host–guest ratio, which increased the glass transition temperature by more than 10 °C compared to that of poly‐ 1 . AFM visualized that (poly‐ 1 )_n?poly‐(R)‐ 2 formed the networked structure on mica. The (poly‐ 1 )_n?poly‐(R)‐ 2 gelled in 1,1,2,2‐tetrachloroethane, which led to fabrication of distinct viscoelastic materials that demonstrated self‐healing behavior in a tensile test.     

Supramolecular Graft Copolymerization of a Polyester by Guest‐Selective Encapsulation of a Self‐Assembled Capsule

Repeating guest units of polyesters poly‐(R )‐ 2 were selectively encapsulated by capsule 1 (BF₄)₄ to produce supramolecular graft polymers. The encapsulation of the guest units was confirmed by ¹H NMR spectroscopy. The graft polymer structures were confirmed by the increase in the hydrodynamic radii and the solution viscosities of the polyesters upon complexation of the capsule. After the capsule was formed, atomic force microscopy showed extension of the polyester chains. The introduction of the graft chains onto poly‐(R )‐ 2 resulted in the main chain of the polymer having an M ‐helical morphology. The complexation of copolymers poly‐[(R )‐ 2 ‐co ‐(S )‐ 2 ] by the capsule gave rise to the unique chiral amplification known as the majority‐rules effect.     

Cooperative Self‐Assembly of a Quaternary Complex Formed by Two Cucurbit[7]uril Hosts,Cyclobis(paraquat‐p‐phenylene), and a “Designer” Guest

The self‐assembly in aqueous solution of the well‐known cyclophane, cyclobis(paraquat‐p‐phenylene) (BB⁴⁺), and two cucurbit[7]uril (CB7) hosts around a simple hydroquinol‐based, diamine guest (GH₂²⁺) was investigated by ¹H NMR and electronic absorption spectroscopies, electrospray mass spectrometry and DFT computations. The formation of a quaternary supramolecular assembly [GH₂²⁺⋅BB⁴⁺⋅ (CB7)₂] was shown to be a very efficient process, which takes place not only because of the attractive forces between each of the hosts and the guest, but also because of the lateral interactions between the hosts in the final assembly. This complementary set of attractive interactions results in clear cooperative binding effects that help overcome the entropic barriers for multiple component assembly.     

Supramolecular Block Copolymers from Tricarboxamides. Biasing Co-assembly by the Incorporation of Pyridine Rings

The synthesis of a series of triangular-shaped tricarboxamides endowed with three picoline or nicotine units (compounds 2 and 3 , respectively) or just one nicotine unit (compound 4 ) is reported, and their self-assembling features investigated. The pyridine rings make compounds 2 – 4 electronically complementary with our previously reported oligo(phenylene ethynylene)tricarboxamides (OPE-TA) 1 to form supramolecular copolymers. C₃-symmetric tricarboxamide 2 forms highly stable intramolecular five-membered pseudocycles that impede its supramolecular polymerization into poly-2 and the co-assembly with 1 to yield copolymer poly-1-co-2 . On the other hand, C₃-symmetric tricarboxamide 3 readily forms poly-3 with great stability but unable to form helical supramolecular polymers despite the presence of the peripheral chiral side chains. The copolymer poly-1-co-3 can only be obtained by a previous complete disassembly of the constitutive homopolymers in CHCl₃. Helical poly-1-co-3 arises in a process involving the transfer of the helicity from racemic poly-1 to poly-3 , and the amplification of asymmetry from chiral poly-3 to poly-1 . Importantly, C_2v-symmetric 4 , endowed with only one nicotinamide moiety and three chiral side chains, self-assembles into a P-type helical supramolecular polymer ( poly-4 ) in a thermodynamically controlled cooperative process. The combination of poly-1 and poly-4 generates chiral supramolecular copolymer poly-1-co-4 , whose blocky microstructure has been investigated by applying the previously reported supramolecular copolymerization model.     

Inclusion of Poly(ethylene glycol)s by Crystalline (R)-(1-Naphthyl)glycyl-(R)-phenylglycine

Abstract

Crystallization of (R)-(1-naphthyl)glycyl-(R)-phenyl-glycine [(R,R)-1] in the presence of oligo(ethylene glycol) dimethyl ethers 2(n) or poly(ethylene glycol)s (PEGs, 3(M_n )) afforded inclusion compounds. The ratio of (R,R)-1/the guest polymer (2 or 3) was proportional to the length of the polymer chain. The crystal structure of a hepta(ethylene glycol) dimethyl ether-included compound was disclosed by X-ray crystallography which showed that (R,R)-1 molecules form a sheet and the guest molecule penetrates the crystal lattice of (R,R)-1 through a one-dimensional channel on the sheet. Powder X-ray analysis revealed that, regardless of the length of the guest polymer, the distance between the neighboring sheets remains unchanged (12.0–12.3 Å) in these inclusion crystals. By thermal analysis, it was shown that the decomposition points of these inclusion compounds became higher with the longer PEG included. The inclusion phenomenon enabled the fractionation of PEGs with various molecular weights, among which longer PEG was preferably included.     

Host–guest supramolecular polymers constructed of aniline derivatives and three-dimensional coordination polymers [(n-Bu3Sn)2(R3Sn)Fe(CN)6] n,R = n-Bu or Ph

The straightforward self-assembly reaction of R₃Sn⁺ and [Fe(CN)₆]^3? affords three-dimensional (3-D) coordination polymers [(n-Bu₃Sn)₂(R₃Sn)Fe(CN)₆] _n , R = n-Bu(I) or Ph(II). The architecture of these coordination polymers is closely related to zeolite and acts as a host with wide internal cavities or channels capable of encapsulating voluminous organic compounds. Aniline derivatives acting as guest are encapsulated within the cavities of the 3-D-polymeric hosts I and II by tribochemical reaction producing host–guest supramolecular polymers. The structures and physical properties of these hosts and their host–guest systems were investigated by elemental analysis, X-ray powder diffraction, IR, UV-vis, EPR, and magnetic measurements. The morphology of these systems was examined by scanning electron microscopy (SEM). The interesting feature of these host–guest supramolecular polymers is the enhanced electrical conductivities over those of the 3-D-coordination polymeric hosts upon encapsulation of conductive polymers within their cavities.     

Guest‐Directed Supramolecular Architectures of {W36} Polyoxometalate Crowns

The {W₃₆} isopolyoxotungstate cluster provides a stable inorganic molecular platform for the binding of inorganic and organic guest molecules. This is achieved by a binding pocket formed by six terminal oxo ligands located in the central cavity of the all‐inorganic cation binding host. Previously it was shown that the cluster can specifically bind primary amines and importantly, functionalized diamines through a combination of electrostatic and hydrogen bonding interactions. Here we transform this assembly strategy to utilize the binding of long‐chain alkyldiammonium guest cations to physically define the supramolecular structure of the clusters with respect to each other and demonstrate the structure direction as a function of alkyl chain length. The systematic variation of the chain length gives access to five supramolecular assemblies which were all fully characterized using single crystal XRD, TGA, ¹H NMR, and elemental analysis. In compound 1 , diprotonated 1,8‐diaminooctane molecules link the {W₃₆} clusters into infinite 1D zigzag chains, whereas compounds 2 and 3 feature trimeric {W₃₆} assemblies directly connected through protonated 1,9‐diaminononane ( 2 ) or 1,10‐diaminodecane ( 3 ) linkers . Compound 4 contains dumb‐bell shaped dimeric units as a result of direct center‐to‐center linkages between the {W₃₆} clusters formed by protonated 1,12‐diaminododecane. In compound 5 , triply protonated bis(hexamethylene)triamine was employed to obtain linear 1D chains of directly connected {W₃₆} cluster units.     

Coordination polymers constructed from an asymmetric dicarboxylate and N-donors: preparation,characterization, and properties

Two new coordination polymers with an asymmetric dicarboxylate and 4,4′-bipyridine ligand, {[Co(bpy)(H₂O)₄]·(cpa)·0.5H₂O}_n (1) and {[Ag(cpa)(bpy)][Ag(bpy)]·4H₂O}_n (2) (H₂cpa = 4-(2-carboxyethyl)benzoic acid, bpy = 4,4′-bipyridine), have been hydrothermally synthesized and characterized by elemental analysis, FT-IR spectroscopy, and single-crystal X-ray diffraction. Compound 1 displays a linear chain with guest molecule (cpa)^2? ions existing in the structure. Compound 2 contains two independent units, [Ag(cpa)(bpy)]^– (A) and [Ag(bpy)]⁺ (B), which form a 1-D + 1-D structure. A shows a 1-D chain structure bearing hooks formed by the carboxylates and organized into a tubular structure by hydrogen-bonding interactions. B has linear chains formed from Ag⁺ and bpy. The A and B chains co-crystallize with waters of crystallization to provide two linear [Ag(bpy)]⁺ chains embedded in the tubular structure formed by A via π…π stacking contacts. In 1 and 2, hydrogen-bonding and π…π stacking interactions connect the discrete 1-D chains into 3-D supramolecular structures. The fluorescent properties, TG analysis, and X-ray powder diffraction patterns for 1 and 2 were also measured.     

Cucurbituril‐Modulated Supramolecular Assemblies: From Cyclic Oligomers to Linear Polymers

Employing bis(p‐sulfonatocalix[4]arenes) (bisSC4A) and N′,N′′hexamethylenebis(1‐methyl‐4,4′‐bipyridinium) (HBV⁴⁺) as monomer building blocks, the assembly morphologies can be modulated by cucurbit[n]uril (CB[n]) (n=7, 8), achieving the interesting topological conversion from cyclic oligomers to linear polymers. The binary supramolecular assembly fabricated by HBV⁴⁺ and bisSC4A units, forms an oligomeric structure, which was characterized by NMR spectroscopy, atomic force microscopy (AFM), transmission electron microscopy (TEM), dynamic light scattering (DLS), isothermal titration calorimetry (ITC), and gel permeation chromatography (GPC) experiments. The ternary supramolecular polymer participated by CB[8] is constructed on the basis of host–guest interactions by bisSC4A and the [2]pseudorotaxane HBV⁴⁺@CB[8], which is characterized by means of AFM, DLS, NMR spectroscopy, thermogravimetric analysis (TGA), UV/Vis spectroscopy, and elemental analysis. CB[n] plays vital roles in rigidifying the conformation of HBV⁴⁺, and reinforcing the host–guest inclusion of bisSC4A with HBV⁴⁺, which prompts the formation of a linear polymer. Moreover, the CB[8]‐participated ternary assembly could disassemble into the molecular loop HBV²⁺@CB[8] and free bisSC4A after reduction of HBV⁴⁺ to HBV²⁺, whereas the CB[7]‐based assembly remained unchanged after the reduction. CB[8] not only controlled the topological conversion of the supramolecular assemblies, but also improved the redox‐responsive assembly/disassembly property practically.     

Thermoresponsive Supramolecular Dendronized Polymers

Combining the concepts of supramolecular polymers and dendronized polymers provides the opportunity to create bulky polymers with easy structural modification and tunable properties. In the present work, a novel class of side‐chain supramolecular dendronized polymethacrylates is prepared through the host–guest interaction. The host is a linear polymethacrylate (as the backbone) attached in each repeat unit with a β‐cyclodextrin (β‐CD) moiety, and the guest is constituted with three‐fold branched oligoethylene glycol (OEG)‐based first‐ (G1) and second‐generation (G2) dendrons with an adamantyl group core. The host and guest interaction in aqueous solution leads to the formation of the supramolecular polymers, which is supported with ¹H NMR spectroscopy and dynamic light scattering measurements. The supramolecular formation was also examined at different host/guest ratios. The water solubility of hosts and guests increases upon supramolecular formation. The supramolecular polymers show good solubility in water at room temperature, but exhibit thermoresponsive behavior at elevated temperatures. Their thermoresponsiveness is thus investigated with UV/Vis and ¹H NMR spectroscopy, and compared with their counterparts formed from individual β‐CD and the OEG dendritic guest. The effect of polymer concentration and molar ratio of host/guest was examined. It is found that the polar interior of the supramolecules contribute significantly to the thermally‐induced phase transitions for the G1 polymer, but this effect is negligible for the G2 polymer. Based on the temperature‐varied proton NMR spectra, it is found that the host–guest complex starts to decompose during the aggregation process upon heating to its dehydration temperature, and this decomposition is enhanced with an increase of solution temperature.     

Synthesis,crystal structure and magnetic property of a three-dimensional cagelike polymer [Co(4,4′-bpy)(NCS)<Subscript>2</Subscript>(py)<Subscript>2</Subscript>](inn)

A new organic-inorganic hetero-coordination polymer with three different kinds of ligands [Co(4,4′-bpy)(NCS)₂(py)₂]_n is synthesized in the extremely mild condition. The X-ray diffraction reveals that the title polymer has a highly tactic three-dimensional cagelike supramolecular structure. Although the coordination bond makes it a one-dimension chain, the hydrogen bond plays an important role in the formation of 3-D supramolecular frameworks. The determination of magnetic properties has been carried out, and shows that it behaves weak antiferromagnetic property with J _{4,4′ -bpy} = -3.8cm^-1.     

Construction of anion‐responsive crosslinked polypseudorotaxane based on molecular recognition of pillar[5]arene

A pillar[5]arene pendant polymer (Poly‐P[5]A) is synthesized via ROMP using Grubb's first‐generation catalyst. GPC analysis of the polymer suggested ~30 pendant pillar[5]arene units in the polymer. Supramolecular polypseudorotaxane assembly is constructed by intermolecularly crosslinking pendant pillar[5]arene units using a bispyridinium guest via host–guest complexation. Formation of the polypseudorotaxane assembly is characterized by 1D/2D NMR techniques and DLS analysis. Moreover, anion‐responsiveness of the polypseudorotaxane assembly is demonstrated by ¹H NMR spectroscopic analysis using chloride anion as external stimulus. Scanning electron microscopic analysis of the poly‐P[5]A showed breath‐figure assembly and upon crosslinking with G.2PF₆ the polymer self‐assemble to give a supramolecular polymer network. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 1508–1515     

Hydrogen‐Bond and Metal–Ligand Coordination Bond Hybrid Supramolecular Capsules: Identification of Hemicapsular Intermediate and Dual Control of Guest Exchange Dynamics

Hybrid supramolecular capsules self‐assemble by simultaneously forming hydrogen and metal–ligand coordination bonds on mixing a C₂‐symmetrical cavitand (calix[4]resorcinarene‐based cavitands with ureide and terminal 4‐pyridyl units) with platinum or palladium complexes ([Pt(OTf)₂] or [Pd(OTf)₂] with chelating bisphosphines) in 1:1 ratio. Hemicapsular assemblies formed in the presence of excess amounts of cavitand relative to the platinum or palladium complexes are identified as intermediates in the above self‐assembly process by 2D‐NOESY spectroscopy. External‐anion‐assisted encapsulation of a neutral guest, 4,4′‐diiodobiphenyl, inside the hybrid supramolecular capsules accompanied conformational changes in the hydrogen‐bonding moieties. The in/out exchange ratio of the encapsulated guest depends on the bite angle of the bisphosphine ligand. Addition of DMSO accelerates guest exchange by weakening the hydrogen bonds in the encapsulation complex. Therefore, variations in the structure of the metal complex and amount of polar solvent exert dual control on the dynamics of the guest exchange.     

Host–guest interaction-mediated fabrication of aggregation-induced emission supramolecular hydrogel for use as aqueous light-harvesting systems

ABSTRACT

Aqueous light-harvesting systems in hydrogels formed by specific noncovalent interactions exhibit both solution and solid-state performance. In this work, the copolymerisation of acrylamide (AM), 4-(1,2,2-triphenylvinyl) phenyl acrylate (vTPE), and guest units 1-benzyl-3vinylimidazolium (G) was carried out with initiator to form P(AM-vTPE-G). Then, supramolecular hydrogels were fabricated by dynamic host–guest interactions the guest unit and host molecule cucurbit[8]uril (CB[8]). The aggregated tetraphenylethylene (TPE) moieties in the polymer chains aggregate together, possessed high fluorescence enhancement during the cross-linking process. Meanwhile, emission characteristics of the obtained aqueous light-harvesting systems were further examined by using the donor (supramolecular hydrogel) and acceptor (Eosin Y disodium salt) system. The process provides a novel method for the production of fluorescence and self–healing supramolecular hydrogel with various potential applications.     

Selective synthesis of structurally isomeric poly-β-ester and poly-δ-ester from β-(2-acetoxy-ethyl)-β-propiolactone with Al and Zn catalysts

It was found that structurally isomeric polymers were formed by the ring-opening polymerization of β-(2-acetoxy ethyl)-β-propiolactone with (EtAlO)_n and Et(ZnO)₂ZnEt catalysts; that is, the Al catalyst catalyzed normal polymerization which led to poly-β-ester and the Zn catalyst formed isomerized poly-β-ester as the main product. The polymer structure was determined by nuclear magnetic resonance (NMR), T₁-value, thermal decomposition product, and (T_g). The NMR studies for the monomer–catalyst systems indicated that the Al catalyst interacted predominately with the lactone group, whereas the Zn catalyst interacted with the side-chain ester group. These site-selective interactions could be related to the difference in the stereoregulation by the two catalysts during the poly(β-ester)-forming polymerization process.     

Crystal structure and magnetic properties of the novel mixed-valence copper coordination polymer constructed from two kinds of inorganic units

A novel mixed-valence Cu^I/Cu^II coordination polymer [Cu^I(μ₂-Cl)Cu^II(μ₃-S)(Phen)] _n (I) (Phen = 1,10-phenanthroline) has been hydrothermally synthesized and structurally characterized by elemental analyses and single-crystal X-ray diffraction. Single-crystal X-ray diffraction analysis reveals that a unique one-dimensional infinite chain-like structure is constructed by two unusual zigzag chains of [CuCl] _n and [CuS] _n . Both of the zigzag chains are used as the second building units (SBU) to produce a 2D helix-like layer at the aid of the C-H...Cl hydrogen bonding interactions between Phen groups and [CuCl] _n chains. An interesting three-dimensional network is formed with the supramolecular van der Waals contacting among the 2D layers. Finally, the magnetic properties of the title compound have been investigated in the temperature range 2–300 K.     

Synthesis, characterization, properties and crystal structure of heterometallic 1D coordination polymers {[CuLZn·CuLZn(H2O)]·H2O}n

Copper-zinc heterometallic 1D chain coordination polymer has been synthesized and characterized by elemental analysis, and IR spectra etc. The crystal structure was determined by single-crystal X-ray diffraction analyses. The title complex is 1D chain coordination polymer with the chemical formula {[CuLZn·CuLZn(H₂O)]·H₂O}_n, where H₄L=N-(2-hydroxybenzamido)-N′-(3-carboxylsalicylidene)ethylenediamine. Its structural unit is comprosed of two tetranuclear cycles formed by two dissymmetrical tetranuclear units. These units polymerized each other to form 1D chain coordination polymer.     

A Multiple‐Responsive Self‐Healing Supramolecular Polymer Gel Network Based on Multiple Orthogonal Interactions

Supramolecular polymer networks have attracted considerable attention not only due to their topological importance but also because they can show some fantastic properties such as stimuli‐responsiveness and self‐healing. Although various supramolecular networks are constructed by supramolecular chemists based on different non‐covalent interactions, supramolecular polymer networks based on multiple orthogonal interactions are still rare. Here, a supramolecular polymer network is presented on the basis of the host–guest interactions between dibenzo‐24‐crown‐8 (DB24C8) and dibenzylammonium salts (DBAS), the metal–ligand coordination interactions between terpyridine and Zn(OTf)₂, and between 1,2,3‐triazole and PdCl₂(PhCN)₂. The topology of the networks can be easily tuned from monomer to main‐chain supramolecular polymer and then to the supramolecular networks. This process is well studied by various characterization methods such as ¹H NMR, UV–vis, DOSY, viscosity, and rheological measurements. More importantly, a supramolecular gel is obtained at high concentrations of the supramolecular networks, which demonstrates both stimuli‐responsiveness and self‐healing properties.

     

Synthesis, characterization, properties and crystal structure of heterometallic 1D coordination polymers {[CuLZn·CuLZn(H2O)]·H2O}n

Copper-zinc heterometallic 1D chain coordination polymer has been synthesized and characterized by elemental analysis, and IR spectra etc. The crystal structure was determined by single-crystal X-ray diffraction analyses. The title complex is 1D chain coordination polymer with the chemical formula {[CuLZn·CuLZn(H₂O)]·H₂O}_n, where H₄L=N-(2-hydroxybenzamido)-N′-(3-carboxylsalicylidene)ethylenediamine. Its structural unit is comprosed of two tetranuclear cycles formed by two dissymmetrical tetranuclear units. These units polymerized each other to form 1D chain coordination polymer.     

Polymerization by alkaline earth metal compounds—II Polymerization of 2- and 4-vinylpyridine,styrene and butadiene by triphenylmethyl derivatives of calcium,strontium and barium

Investigations are reported on polymerizations of 2- and 4- vinylpyridine, styrene and butadiene by a series of related alkaline earth metal initiators, Ph₃CMX(THF)_n (M = Ca, Ba, X = Cl, n = 2; M = Ca, X = Br, n = 4; M = Sr, X = Cl, n = 4; M = Sr, X = Br, n = 5) in tetrahydrofuran (THF) or 1,2-dimethoxyethane (DME) at various temperatures and in the absence of solvent. The polymers have been examined by GPC and aspects of their microstructures determined by ¹³C and/or ¹H NMR spectroscopy and, for polybutadiene, i.r. spectroscopy. Poly-2-vinylpyridine produced by Ph₃CMX(THF)_n is rich in isotactic content; the isotacticity is higher for polymer formed in THF than DME solution, falls with change of initiator in the order M = Ca > Sr > Ba and, in DME, is greater when X = Br. The tacticities of poly-4-vinylpyridine and polystyrene are similar to those obtained from related organometallic initiators. The 1,4-content of polybutadiene decreases with initiator Ph₃CMX(THF)_n in the order M = Ba > Sr > Ca; the trans-1,4 structure generally predominates except when M = Ba from which cis-1,4 links are formed in comparable amounts.