Supramolecular Controlled Water Uptake of Macroscopic Materials by a Cyclodextrin-Induced Hydrophobic-to-Hydrophilic Transition

Multicharged cyclodextrin supramolecular assemblies

Multicharged cyclodextrin (CD) supramolecular assemblies, including those based on positively/negatively charged modified mono-6-deoxy-CDs, per-6-deoxy-CDs, and random 2,3,6-deoxy-CDs, as well as parent CDs binding positively/negatively charged guests, have been extensively applied in chemistry, materials science, medicine, biological science, catalysis, and other fields. In this review, we primarily focus on summarizing the recent advances in positively/negatively charged CDs and parent CDs encapsulating positively/negatively charged guests, especially the construction process of supramolecular assemblies and their applications. Compared with uncharged CDs, multicharged CDs display remarkably high antiviral and antibacterial activity as well as efficient protein fibrosis inhibition. Meanwhile, charged CDs can interact with oppositely charged dyes, drugs, polymers, and biomacromolecules to achieve effective encapsulation and aggregation. Consequently, multicharged CD supramolecular assemblies show great advantages in improving drug-delivery efficiency, the luminescence properties of materials, molecular recognition and imaging, and the toughness of supramolecular hydrogels, in addition to enabling the construction of multistimuli-responsive assemblies. These features are anticipated to not only promote the development of CD-based supramolecular chemistry but also contribute to the rapid exploitation of these assemblies in diverse interdisciplinary applications.

Poly(β-Cyclodextrin) Prepared by Ring-Opening Metathesis Polymerization Enables Creation of Supramolecular Polymeric Networks

The controlled synthesis of polymers containing densely grafted cyclodextrin units has proven challenging due to the steric hindrance of these cyclic oligosaccharides. In this study, we report the controlled synthesis of poly(β-cyclodextrin) [poly(β-CD)] through ring-opening metathesis polymerization (ROMP) using Grubbs third-generation catalyst. Molecular weights of >10⁵ g/mol were obtained with dispersity values (Đ) of ≤1.2. In aqueous solution, β-cyclodextrin forms a host-guest complex with adamantyl groups (Ad). These interactions were utilized to prepare supramolecular polymer networks (SPNs) made by adding poly(β-CD) to α,ω-adamantyl-functionalized poly(2-hydroxyethyl acrylate) (Ad-PHEA-Ad). These poly(β-CD)/Ad-PHEA-Ad SPNs were prepared in aqueous solution and then dried to make homogeneous, transparent films. Varying the ratios of the two components enabled structure-property studies via tensile measurements.

Dynamic hydrogels mediated by macrocyclic host-guest interactions

Hydrogels have attracted increasing research interest in recent years due to their dynamic properties and potential applications in biomaterials. Concurrently, macrocycle-based host-guest interactions have played an important role in the development of supramolecular chemistry. Recently, research towards dynamic hydrogels mediated by various macrocyclic host-guest interactions has been gradually disclosed. In this review, we will outline the burgeoning progress in the development of functional hydrogels mediated by various host molecules, such as cyclodextrins, cucurbit[n]urils, calix[n]arenes, pillar[n]arenes, and other macrocycles. Smart hydrogels with outstanding properties, like biocompatibility, toughness, and self-healing, are mainly focused. We believe that this review will highlight the potential of dynamic hydrogels mediated by macrocycle-based host-guest interactions.

Shape Memory Polymers Based on Supramolecular Interactions

Shape memory polymers (SMPs), with the capability to change from one or more temporary shapes to predetermined shapes in response to an external stimulus, have attracted much interest from both academia and industries. When introducing supramolecular interactions that have been featured as dynamic and reversible into the design of novel SMPs, intriguing and unique functionalities have been engendered and thereby broaden the potential applications of the SMPs to new territories. In this review, we summarize recent progress made in SMPs based on supramolecular interactions, provide insight into the material design and shape memory mechanism, elucidate and evaluate their properties and performance, and point out opportunities and applications of SMPs.

An ionic coordination hybrid hydrogel for bioseparation

An ionic coordination hybrid hydrogel is formed with ionic and covalent crosslinked networks via one-step copolymation.

Macroscopic switches constructed through host–guest chemistry

In this feature article, we discuss recent developments in macroscopic contact angle switches formed by different macrocyclic hosts and highlight the properties of these new functional surfaces and their potential applications.

Recyclable Capture and Destruction of Aqueous Micropollutants Using the Molecule-Specific Cavity of Cyclodextrin Polymer Coupled with KMnO4 Oxidation

The removal of aqueous micropollutants remains challenging because of the interference of natural water constituents that are typically 3-9 orders of magnitude more concentrated. Cyclodextrins, which feature molecular recognition and are widely applied in separation and catalysis, are promising materials in the development of pollutant treatment technologies. Here, we described the facile integration of cyclodextrin polymer (CDP) adsorption and KMnO4 oxidation for recyclable capture and destruction of aqueous micropollutants (i.e., antibiotics and TBBPA). CDP exhibited adsorption efficiencies of 0.81-88% and 0.81-94% toward 14 pollutants at 50.0 ng/L and 50.0 μg/L, respectively, at a solid-to-liquid ratio of 1:1250. The presence of simulated or natural water constituents (e.g., Mg(2+), Ca(2+), DOC, and a combination thereof) did not decrease the adsorption potential of CDP toward these pollutants because the pollutants, based on molecular specificity, were entrapped in the CD cavity. Subsequent KMnO4 oxidation completely degraded the retained pollutants, demonstrating that the pollutants could be broken down in the cavity. Pristine CDP was rearranged into the structurally loose composites that featured a porous CDP architecture with uniform embedment of δ-MnO2 nanoparticles and different adsorption efficiencies. δ-MnO2 loading was a linear function of the number of times the integrated procedure was repeated, underlying the accurate control of CDP recycling. Thus, this approach may represent a new method for the removal of aqueous micropollutants.

ATP-triggered biomimetic deformations of bioinspired receptor-containing polymer assemblies

Designing synthetic polymer assemblies that can sense a biological signal to mimic cell activities is elusive. We develop a class of block copolymer containing bioinspired host units as supramolecular catchers for the highly-selective capture of adenosine-5'-triphosphate (ATP). Driven by ATP, these block copolymers undergo a stepwise self-assembly and exhibit cascading deformation into highly-ordered nanostructures via the specific recognition effect between ATP and the receptor. By modulating the ATP concentration, one can precisely control the biomimetic evolution of these assemblies in diverse dimensionalities and geometries, like certain organellar deformations. Moreover, the ATP/polymer hybrid aggregates can be reversibly disassembled in response to phosphatase. The special ability of the artificial assemblies to sense intracellular bioactivators can offer new insight into bio-responsive nanomaterials for cellular applications.

Selective Secondary Face Modification of Cyclodextrins by Mechanosynthesis

α-, β-, and γ-cyclodextrins (CDs) were modified on their secondary face by mechanosynthesis at room temperature using a laboratory-scale ball-mill. Mono-2-tosylated α-, β-, and γ-CDs were obtained in good yield from mixtures of native α-, β-, and γ-CDs, respectively, N-tosylimidazole, and an inorganic base, with each of them being in the solid state. The yields appeared to be dependent upon the nature of the base and the reaction time. A kinetic monitoring by (1)H NMR spectroscopy demonstrated that the highest yields in mono-2-tosyl-CDs were measured using KOH as a base in very short reaction times (up to 65% in 80 s). Mono-(2,3-manno-epoxide) α-, β-, and γ-CDs were subsequently synthesized by ball-milling a mixture of monotosylated α-, β-, and γ-CDs, respectively, and KOH. The characterization of the modified CDs was carried out by X-ray diffraction, mass spectrometry, solid-state NMR, and diffuse reflectance UV-vis (DR UV-vis) spectroscopies. Clues to the supramolecular arrangement of the molecules in the solid state provide information on the reaction mechanism.

Supramolecular assembly of crosslinkable monomers for degradable and fluorescent polymer nanoparticles

Intermolecular B-N coordination has been recognized as a promising driving force for molecular self-organization. However, direct utilization of this intermolecular interaction as building bridge for the supramolecular self-assembly of chemical functionalities to form nano-sized architectures remains a daunting challenge. Here, we outline a multiple intermolecular B-N coordination based supramolecular system, where small boronate molecules can be brought together in solution to form nanoparticles with controllable sizes and morphologies. We not only demonstrate the intrinsic switchable fluorescence and the stimuli-responsive capabilities of the designed boronate molecule, but also show that the stabilized or surface functionalized nanoparticles are degradable in response to pH and D-glucose and able to retain the fluorescence features of the boronate molecule. Additionally, the degraded nanoparticles can repair themselves through the reformation of B-N coordination.

Stretchable and semitransparent conductive hybrid hydrogels for flexible supercapacitors

Conductive polymers showing stretchable and transparent properties have received extensive attention due to their enormous potential in flexible electronic devices. Here, we demonstrate a facile and smart strategy for the preparation of structurally stretchable, electrically conductive, and optically semitransparent polyaniline-containing hybrid hydrogel networks as electrode, which show high-performances in supercapacitor application. Remarkably, the stability can extend up to 35,000 cycles at a high current density of 8 A/g, because of the combined structural advantages in terms of flexible polymer chains, highly interconnected pores, and excellent contact between the host and guest functional polymer phase.

Spontaneous structuration in coacervate-based protocells by polyoxometalate-mediated membrane assembly

Molecularly crowded, polyelectrolyte/ribonucleotide-enriched membrane-free coacervate droplets are transformed into membrane-bounded sub-divided vesicles by using a polyoxometalate-mediated surface-templating procedure. The coacervate to vesicle transition results in reconstruction of the coacervate micro-droplets into novel three-tiered micro-compartments comprising a semi-permeable negatively charged polyoxometalate/polyelectrolyte outer membrane, a sub-membrane coacervate shell, and an internal aqueous lumen. We demonstrate that organic dyes, ssDNA, magnetic nanoparticles and enzymes can be concentrated into the interior of the micro-compartments by sequestration into the coacervate micro-droplets prior to vesicle formation. The vesicle-encapsulated proteins are inaccessible to proteases in the external medium, and can be exploited for the spatial localization and coupling of two-enzyme cascade reactions within single or between multiple populations of hybrid vesicles dispersed in aqueous media.

Facile synthesis of well-defined cyclodextrin-pendant polymer via ATRP for nanostructure fabrication

PEG-b-PCD block copolymer could be synthesized by ATRP of a new methacrylate–CD monomer, and self-assembled into advanced nanostructures with various guest molecules.

Control the wettability of poly(n-isopropylacrylamide-co-1-adamantan-1-ylmethyl acrylate) modified surfaces: the more Ada, the bigger impact?

Surface-initiated SET-LRP was used to synthesize polymer brush containing N-isopropylacrylamide and adamantyl acrylate using Cu(I)Cl/Me6-TREN as precursor catalyst and isopropanol/H2O as solvent. Different reaction conditions were explored to investigate the influence of different parameters (reaction time, catalyst concentration, monomer concentration) on the polymerization. Copolymers with variable 1-adamantan-1-ylmethyl acrylate (Ada) content and comparable thickness were synthesized onto silicon surfaces. Furthermore, the hydrophilic and bioactive molecule β-cyclodextrin-(mannose)7 (CDm) was synthesized and complexed with adamantane via host-guest interaction. The effect of adamantane alone and the effect of CDm together with adamantane on the wettability and thermoresponsive property of surface were investigated in detail. Experimental and molecular structure analysis showed that Ada at certain content together with CDm has the greatest impact on surface wettability. When Ada content was high (20%), copolymer-CDm surfaces showed almost no CDm complexed with Ada as the result of steric hindrance.