Linear Supramolecular Polymers Research Articles

An AIE fluorescent supramolecular polymer constructed by host-guest interactions among pillar[5]arenes/sulfonium salts for Pd2+ detection

An AIE fluorescent supramolecular polymer was fabricated on the interplay of pillar[5]arenes and sulfonium salts, manifesting substantially heightened fluorescence emissions. The linear supramolecular polymer exhibited significant fluorescence quenching with the addition of competitive molecules. Furthermore, the 1,2,3-triazole groups bestowed the supramolecular polymer with the valuable capability of detecting Pd2+ ions.

Carbazole diester strapped calix[4]pyrrole: Synthesis, anion binding and self-assembly based on ion pair recognition

A new carbazole strapped calix[4]pyrrole 1 has been synthesized and ion binding properties was investigated using 1H NMR, isothermal titration calorimetry and single crystal X-ray diffraction analyses. Compared to the parent octamethyl calix[4]pyrrole 2, receptor 1 showed enhanced binding towards halide anions. Solid state structural analysis revealed that receptor 1 is capable of binding various halide salts showing different binding modes depending on the bound ion pairs. Interestingly, complexes of tetrabutyammonium (TBA+), tetraethylammonium (TEA+) and tetramethylammonium (TMA+) salts of chloride anion displayed three distinctly different binding geometries in the solid state. As a result, the linear supramolecular polymers seen in the crystal lattices are also dramatically different for these three chloride complexes of 1. Combination of 1H NMR and solid state studies revealed that binding of anion in one condition do not translates to another completely. Receptor 1 also found to form 1/1 complexes with CsCl, CsBr and CsI salts and 1D coordination polymer chains are stabilized in the solid state. Overall, construction of four different 1D linear chains are described for chloride anion based on ion pair recognition. In addition, the solid state structure of ion pair complex with CsI salt is unprecedented in the calix[4]pyrrole chemistry. Moreover, under solid-to-liquid extraction condition, receptor 1 is able to solubilise CsF and CsCl ion pairs in chloroform in which these salts are otherwise insoluble.

Multistep sequence-controlled supramolecular polymerization by the combination of multiple self-assembly motifs

The precise sequence control of polymer chain is an important research topic of polymer chemistry. Although some methods such as iterative synthesis and supramolecular polymerization have been developed to fabricate sequence-controllable polymer, it is still a great challenge to consecutively prepare multiple supramolecular polymers with different sequence structures. In this work, through the reasonable utilization of assembly motifs, we integrated multiple host-guest recognitions and metal coordination interactions to prepare different sequence-controlled supramolecular polymers by a multistep assembly strategy. This research provides inspiration for the design and preparation of supramolecular polymers with different sequence structures.

Dimeric Pillar[5]arene as a Novel Fluorescent Host for Controllable Fabrication of Supramolecular Assemblies and Their Photocatalytic Applications.

A dimeric fluorescent macrocycle m-TPE Di-EtP5 (meso-tetraphenylethylene dimeric ethoxypillar[5]arene) is synthesized based on the meso-functionalized ethoxy pillar[5]arene. Through the connectivity of two pillar[5]arenes by CC double bond, the central tetraphenylethylene (TPE) moiety is simultaneously formed. The resultant bicyclic molecule not only retains the host-guest properties of pillararenes but also introduces the interesting aggregation-induced emission properties inherent in the embedded TPE structure. Three dinitrile derivatives with various linkers are designed as guests (G1, G2, and G3) to form host-guest assemblies with m-TPE Di-EtP5. The morphological control and fluorescence properties of the assemblies are successfully realized. G1 with a shorter alkyl chain as the linker completely threads into the cavities of the host. G2, due to its longer chain length, forms a linear supramolecular polymer upon binding to m-TPE Di-EtP5. G3 differs from G2 by possessing a bulky phenyl group in the middle of the chain, which can be further assembled with m-TPE Di-EtP5 to form supramolecular layered polymer and precipitated out in solution, and can be efficiently applied to photocatalytic reactions.

Host-guest properties of pagoda[4]arene with α,ω-dibromoalkanes and their self-assembled linear supramolecular polymer driven by guest halogen–halogen interactions

Herein we report the host-guest interactions of pagoda[4]arene with various α,ω-dibromoalkanes. The guest encapsulation properties were probed by 1H NMR titration and isothermal titration calorimetry (ITC) experiments. Unlike pillararenes, the deeper cavity of pagoda[4]arene shows higher affinity toward longer straight-chain molecules with 1:1 host-to-guest stochiometric ratio of complexation. In addition, the formation of the self-assembled supramolecular polymer driven by guest halogen-halogen interactions in solution was demonstrated by diffusion-ordered spectroscopy (DOSY), ITC, and dynamic light scattering (DLS) measurements. From the ITC dilution experiments, we found that the supramolecular polymer dissociation process is mainly entropically driven (TΔS = 64.00 kJ mol−1) and enthalpically disfavored (ΔH = 43.91 kJ mol−1).

A poly-pseudorotaxane constructed by threading pillar[5]arene onto an ion-pair recognition-based calix[4]pyrrole supramolecular polymer.

The ion-pair recognition ability of calix[4]pyrrole was utilized to form a multicomponent monomeric assembly and a linear supramolecular polymer via concurrent anion and bis-cation complexation. The inherent dynamic interactions of these assemblies were further used to construct pseudorotaxanes in monomeric and supramolecular polymer forms with pillar[5]arene.

5]Rotaxane, linear polymer and supramolecular organic framework constructed by nor-seco-cucurbit[10]uril-based ternary complexation

Here we use nor-seco-cucurbit[10]uril (ns-CB[10]) based ternary complexation to construct [5]rotaxane, linear supramolecular dynamic rotaxane polymers and cubic 3D supramolecular organic framework. A [5]rotaxane is constructed by ns-CB[10], TMeCB[6] and short linear derivatives of 4,4′-bipyridinium (M2). ns-CB[10], CB[7] and long linear derivatives of 4,4′-bipyridinium (M3) self-assemble into a linear supramolecular dynamic rotaxane polymer. ns-CB[10] and tetracationic tetrahedral monomer self-assemble and form a three-dimensional supramolecular organic framework. The above results demonstrate that ns-CB[10]-based ternary complexation is a versatile platform to build various supramolecular systems.

Two-step, sequential, efficient, artificial light-harvesting systems based on twisted cucurbit[14]uril for manufacturing white light emission materials

White-light-emitting (WLE) materials have promising and valuable applications in controllable lighting, screen displays and sensing. In this study, a two-step sequence of highly efficient artificial light-harvesting systems (ALHSs) with white light emission is successfully constructed in the aqueous phase through a non-covalent bond among imidazole derivatives (DIm), twisted cucurbit[14]uril (tQ[14]), eosin Y (ESY), and Nile red (NiR). The prepared linear supramolecular polymer (DIm@tQ[14]) constructed by DIm and tQ[14] through host–guest interaction is an ideal energy donor due to its superior aggregation-induced emission effect, which enables one-step energy transfer by loading ESY and two-step energy transfer by further loading NiR with a high efficiency of 91.47%. The emission color of the two-step sequential ALHSs changes from cyan to chartreuse then to orange-red, and bright white light emission can be achieved by controlling the donor/acceptor molar ratio. Moreover, the assemblies of the two-step sequential ALHSs can be applied to white LED materials. This research not only simulates the multi-step energy transfer process in nature but also has an attractive commercial value in the manufacturing of WLE materials.

An efficient supramolecular artificial light-harvesting system based on twisted cucurbit[15]uril and cucurbit[10]uril for live cell imaging

The construction of highly efficient artificial light-harvesting systems in aqueous solutions is still challenging. Herein, we reported a new light-harvesting system based on the supramolecular combination of twisted cucurbit[15]uril (tQ[15]), cucurbit[10]uril (Q[10]), and an anthracene derivative (APy) with aggregation-induced emission (AIE) properties. The Q[n]-based linear supramolecular polymer, APy@tQ[15]@Q[10], was constructed through a two-step assembly strategy. Subsequently, a highly efficient artificial light-harvesting system with relatively high antenna effect and energy transfer efficiency was successfully constructed through non-covalent interactions between Rhodamine B (RB, acceptor) and the APy@tQ[15]@Q[10] (donor). The resulting system was compatible with HeLa cells and could be used for live-cell imaging in the red channel. This supramolecular assembly strategy has not only produced a highly efficient light-harvesting system but also expands the application of Q[n]s in the biomedical field.

Linear Supramolecular Polymer Driven by Br⋅⋅⋅Br and Br⋅⋅⋅H Non-bonding Interactions Based on Inclusion-Complex of Octabromo-Functionalized Pillar[a]rene

Linear Supramolecular Polymer Driven by Br⋅⋅⋅Br and Br⋅⋅⋅H Non-bonding Interactions Based on Inclusion-Complex of Octabromo-Functionalized Pillar[a]rene

Detection of Aliphatic Aldehydes by a Pillar[5]arene-based Fluorescent Supramolecular Polymer with Vaporchromic Behavior.

The detection of volatile aliphatic aldehydes is of significance because of their chemical toxicity, physical volatility and widespread applications in chemical industrial processes. In this work, the direct detection of aliphatic aldehydes is tackled using a pillar[5]arene-based fluorescent supramolecular polymer with vaporchromic behavior. Thin films with strong orange-yellow fluorescence are prepared by coating the linear supramolecular polymer on glass sheets. When the thin films are exposed to aliphatic aldehydes with different carbon chain lengths, they can selectively sensing n-butyraldehyde (C4 ) and caprylicaldehyde (C8 ), accompanied by fluorescence quenching, indicating that the supramolecular polymer is a highly selective vapochromic response material for aliphatic aldehydes with long alkyl chains.

Branched Supramolecular Copolymers: Inducing Branching in Bisurea-Based Monomers Using Multi-Sulfonate Molecules

Supramolecular polymers are based on noncovalent interactions, which impart unique properties such as dynamic behavior, concentration-dependent degree of polymerization, and environmental responsiveness. While linear supramolecular polymers are ubiquitous and have been extensively studied, branched polymers that are based exclusively on supramolecular interactions are much less abundant, and a fundamental understanding of their molecular-level structure is still lacking. We report on the preparation of branched, all-supramolecular polymers based on a combination of a bisureidotoluene building block [N,N′-2,4-bis((2-ethylhexyl)ureido)toluene (EHUT)], which is associated with four-point hydrogen bonding, and three anionic co-monomers featuring one, two, or three sulfonate groups. The co-monomers were designed to serve as a chain stopper, a bifunctional linear co-monomer, and a branch point. Whereas combination of EHUT with the singly functionalized co-monomer led to linear supramolecular chains, diffusion and viscosity data indicate that branched supramolecular polymers were obtained when EHUT was combined not only with the triply functionalized molecules but also with the doubly functionalized molecules. Theoretical analysis based on an adaptation of Flory’s theory of branched polymers suggests that in both cases, the interaction of certain EHUT units with the multiply functionalized co-monomers converted these EHUT units into branch points, which led to substantially reduced viscosities in these systems. The insights gained from this study enable tuning the properties of supramolecular polymers not only by concentration and temperature but also by introducing appropriately designed molecular additives. This may lead to the development of sophisticated smart materials.

Host-Guest Properties of Pagoda[4]Arene with Α,Ω-Dibromoalkanes and Their Self-Assembled Linear Supramolecular Polymer Driven by Guest Halogen–Halogen Interactions

Host-Guest Properties of Pagoda[4]Arene with Α,Ω-Dibromoalkanes and Their Self-Assembled Linear Supramolecular Polymer Driven by Guest Halogen–Halogen Interactions

Topological-skeleton controlled chirality expression of supramolecular hyperbranched and linear polymers

The topology of polymers plays an essential role in their chemical, physical and biological properties. However, their effects on chirality-related functions remain unclear. Here, we reported the topology-controlled chirality expression in the chiral supramolecular system for the first time. Two topological supramolecular polymers, hyperbranched (HP) and linear (LP) supramolecular polymers produced by the host–guest interactions of branched and linear monomers, respectively, exhibited completely different chirality expressions despite the same molecular chirality of their monomers. Significantly, due to the branch points and strong steric hindrance existing in HP, cis-HP showed an enhanced and sign-inverted Cotton effect in the n–π* bands compared with cis-LP, as a result that the distinctive chirality induction and transfer were controlled by the topological skeletons. This topology-controlled chirality induction and transfer in the photoswitchable supramolecular polymers not only enables us to elucidate the in-depth effects of topology on the chiral expression in biopolymers but also inspires the design of chiroptical and bioinspired materials.

Controllable fabrication of a supramolecular polymer incorporating twisted cucurbit[14]uril and cucurbit[8]uril via self-sorting

A linear supramolecular polymer with controllable features based on twisted cucurbit[14]uril (tQ[14]) and cucurbit[8]uril (Q[8]) was firstly fabricated via an effective self-sorting strategy. Herein we designed a monomer, 1‑butyl‑1′-(naphthalen- 2-ylmethyl)-4,4′-bipyridinium bromide (BNB), that contains bipyridyl, aliphatic butyl and aromatic naphthyl groups, simultaneously. Two host molecules, tQ[14] and Q[8] were employed to develop an effective strategy for constructing a linear supramolecular polymer with controllable features. The alkyl groups on both sides of BNB could insert into the two cavities of tQ[14], the naphthyl part of BNB via π-π stacking in Q[8] cavity, serving as the driving force for supramolecular polymerization. Through self-sorting of the monomer, tQ[14] and Q[8], led to the formation of the linear supramolecular polymer. Depolymerization could be achieved by addition of adamantane hydrochloride (AH) which driven two BNB guest molecules out of the Q[8] cavity. This self-sorting strategy has great potential, not only for designing supramolecular polymer materials with different controllable structures through introduction of multiple functional groups, but also for broadening the application of twisted cucurbit[14]uril in supramolecular chemistry.

Triazine-Based Janus G-C Nucleobase as a Building Block for Self-Assembly, Peptide Nucleic Acids, and Smart Polymers.

This communication reports on the utility of a triazine-based self-assembling system, reminiscent of a Janus G-C nucleobase, as a building block for developing (1) supramolecular polymers, (2) peptide nucleic acids (PNAs), and (3) smart polymers. The strategically positioned self-complementary triple H-bonding arrays DDA and AAD facilitate efficient self-assembly, leading to a linear supramolecular polymer.

A calix[4]pyrrole-based linear supramolecular polymer constructed by orthogonal self-assembly.

A calix[4]pyrrole having a ureidopyrimidinone unit was successfully synthesized from its alcohol-functionalized congener and further used for the first time to obtain a thermo- and chemical-responsive linear supramolecular polymer via orthogonal self-assembly comprising a combination of quadruple hydrogen bonding and anion recognition.

Tunable Adhesion from Stoichiometry-Controlled and Sequence-Defined Supramolecular Polymers Emerges Hierarchically from Cyanostar-Stabilized Anion-Anion Linkages.

Sequence-controlled supramolecular polymers offer new design paradigms for generating stimuli-responsive macromolecules with enhanced functionalities. The dynamic character of supramolecular links present challenges to sequence definition in extended supramolecular macromolecules, and design principles remain nascent. Here, we demonstrate the first example of using stoichiometry-control to specify the monomer sequence in a linear supramolecular polymer by synthesizing both a homopolymer and an alternating copolymer from the same glycol-substituted cyanostar macrocycle and phenylene-linked diphosphate monomers. A 2:1 stoichiometry between macrocycle and diphosphate produces a supramolecular homopolymer of general formula (A)n comprised of repeating units of cyanostar-stabilized phosphate-phosphate dimers. Using a 1:1 stoichiometry, an alternating (AB)n structure is produced with half the phosphate dimers now stabilized by the additional counter cations that emerge hierarchically after forming the stronger cyanostar-stabilized phosphate dimers. These new polymer materials and binding motifs are sufficient to bear normal and shear stress to promote significant and tunable adhesive properties. The homopolymer (A)n, consisting of cyanostar-stabilized anti-electrostatic linkages, shows adhesion strength comparable to commercial superglue formulations based on polycyanoacrylate but is thermally reversible. Unexpectedly, and despite including traditional ionic linkages, the alternating copolymer (AB)n shows weaker adhesion strength more similar to commercial white glue based on poly(vinyl acetate). Thus, the adhesion properties can be tuned over a wide range by simply controlling the stoichiometric ratio of monomers. This study offers new insight into supramolecular polymers composed of custom-designed anion and receptor monomers and demonstrates the utility of emerging functional materials based on anion-anion linkages.

Pillar[5]arene-based self-assembled linear supramolecular polymer driven by guest halogen–halogen interactions in solid and solution states

A pillar[5]arene-based linear supramolecular polymer mediated by guest halogen–halogen interactions (C–Br⋯Br–C) was studied in both the solution and solid states.

Preparation of a mechanically interlocked polymer from a linear supramolecular polymer

We transformed a linear supramolecular polymer into a mechanically interlocked polymer by photoisomerization.