Non-covalent Supramolecular Interactions Research Articles

Dynamic covalent epoxy network of hyperbranched-synergistic-supramolecular: Catalyst-free reprocessing, and application in carbon fiber composites recycling

Plastic recycling, especially the recycling of thermosets, is a crucial step towards improving waste management and achieving economic recycling. Here, a method utilizing non-covalent supramolecular interactions and synergistic hyperbranched structures is reported to endow transesterification-based thermosetting materials with recyclability in the absence of a catalyst. A hyperbranched epoxy resin curing agent (HPCA) containing amide bonds, terminated by amine and ester, was designed and synthesized, and further cured with bisphenol A epoxy resin. The hyperbranched topological structure and its abundant amide bonds contribute to the formation of a dense hydrogen bonding network, enhancing the reprocessability, thermal, and mechanical properties of the material. As a result, the resin can be reprocessed by hot pressing at 190 °C and 10 MPa for 40 min without catalyst. Moreover, amide and ester bonds endow resin materials with excellent degradation performance in alkaline solutions, laying the foundation for the recycling and utilization of carbon fibers in composite materials.

A multi-stimulus responsive nanogel actuator with the π-π stacking interaction self-assembly and application for bioinspired smart skin with light, heat and humidity responses and superb UV resistance

The fabrication and development of assemblies of bionic smart skin with multi-stimulus response and multi-color tunable properties is a major challenge in the field of advanced materials and smart wearable devices. In this work, an amphiphilic functional nanogel switch connected by long polyether chain segments containing bis-spiropyran with the π-π stacking interactions was designed. A multi-stimulus responsive color-changing nanogel actuator (SP-PEG-NA) was constructed using ionic liquid-assisted self-assembly. A composite bionic smart skin (WPU/SP-PEG@CF) was prepared by compositing SP-PEG-NA, waterborne polyurethane (WPU) and flexible cotton fabric based on physical cross-linking. The smart skin possesses multiple color-changing properties in response to light, heat and humidity. Even under ultra-low UV intensity (0.025 mW/cm2), WPU/SP-PEG@CF also exhibits significant photochromic properties. Surprising, the smart composite constructed with the nanogels possessed extremely high UV shielding performance (UPF 628.68) and photocontrolled hydrophobic-hydrophilic transition properties. The self-assembled nanogel actuators greatly improved the stimulus–response sensitivity. The multiple supramolecular noncovalent interactions of the nanogel actuator such as hydrophilic long polyether structures hydrogen-bonding and π-π stacking interactions endowed nanogel highly self-assembly properties. They showed excellent multi-stimulus response in color-changing, versatility and reversibility. The multi-stimulus responsive and multifunctional smart composites prepared using self-assembled nanogel has potential applications in smart wearable materials, sensors and information display.

Solvent-Directed Bioactive Supramolecular Zinc(II)-Metallogels: Exploring Semiconducting Aptitudes of Fabricating p-n Junction and Schottky Devices.

α-Ketoglutaric acid-based supramolecular Zn(II) metallogels in N,N'-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) solvent (i.e., Zn-α-Glu-DMF and Zn-α-Glu-DMSO) were successfully achieved. Zinc(II) acetate salt and α-ketoglutaric acid directed a three-dimensional noncovalent supramolecular network individually entrapped with N,N'-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) solvent to accomplish their respective semisolid flexible metallogel frameworks. The gel features of these synthesized materials were verified by rheological experiments such as amplitude sweep and frequency sweep measurements. The discrete morphological arrangements were analyzed for these metallogel samples through field emission scanning electron microscopic (FESEM) analysis. Highly stacked interconnected blocks of Zn-α-Glu-DMF with hierarchical arrays are found due to the occurrence of diverse noncovalent supramolecular interactions present in the metallogel framework. A distinct spherical shaped microstructure with interconnected hierarchical assembly has been observed for the FESEM pattern of Zn-α-Glu-DMSO. FTIR spectroscopic measurement was carried out to detect some important stretching vibrations of xerogel samples of different metallogels as well as gel-constructing chemical ingredients. A substantial amount of peak shifting of xerogel samples for both metallogels is observed in FTIR analysis, indicating the presence of different noncovalent interactions. ESI-mass analysis portrays a possible metallogel-constructing strategy. The antibacterial potentialities of both metallogels were investigated. These materials exhibited good antimicrobial efficacy toward Gram-positive and Gram-negative bacterial strains (including Escherichia coli, Bacillus cereus, Staphylococcus aureus, Listeria monocytogenes, and Salmonella typhimurium). Both synthesized metallogels were successfully implemented to fabricate the photoresponsive semiconducting diode. These materials offer excellent photodiode parameters including an ideality factor and rectification ratio (ON/OFF ratio). Synthesized metallogels are used to successfully fabricate photodiodes with an Al/p-Si/metallogel/Au structure. The ideality factors (η) for Zn-α-Glu-DMF and Zn-α-Glu-DMSO are found as 1.3 and 2.3, respectively, in dark conditions. The rectification ratios for Zn-α-Glu-DMF and Zn-α-Glu-DMSO metallogels are also determined, and these are found as 40 and 10, respectively.

Comparative Vision of Nonlinear Thermo-Optical Features and Third-Order Susceptibility of Mechanically Flexible Metallosupramolecular Self-Repairing Networks with Isomeric Organic Acids.

Two self-healing-type supramolecular Ni(II)-metallogels are achieved. The choice of proper low-molecular-weight organic gelators such as trans-butenedioic acid (i.e., trans-BDA) and cis-butenedioic acid (i.e., cis-BDA) and triethylamine in N,N'-dimethylformamide solvent facilitates the metallogelation process. Through rheological investigations the mechanical robustness and viscoelastic properties of synthesized metallogels are explored. An in-depth exploration of thixotropic behavior also supports their self-healing features. Notably, distinct variations in morphologies of metallogels are also ascertained through field emission scanning electron microscopy studies. Furthermore, the existence of versatile noncovalent supramolecular interactions operating throughout the metallogel network is clearly revealed via Fourier transform infrared spectroscopy. Electrospray ionization-mass studies also explore the construction protocol of individual Ni(II)-metallogels. The Z-scan measurements with a 532 nm continuous wave laser were employed to unveil the nonlinear thermo-optical response of two synthesized self-healing metallogels, i.e., trans-BDA-TEA@Ni(II) and cis-BDA-TEA@Ni(II). Crucial parameters like the nonlinear refractive index, nonlinear absorption coefficient, thermo-optical coefficient, and third-order susceptibility of these metallogels are obtained. Metallogels show negative signs for the nonlinear refractive index and the nonlinear absorption coefficient. The real parts of the third-order susceptibility for these metallogels are much greater than the imaginary parts (i.e., χR(3) > χI(3)), making such metallogels very promising for all optical-switching applications.

Emergence of Dynamic Instability by Hybridizing Synthetic Self-Assembled Dipeptide Fibers with Surfactant Micelles.

Supramolecular chemistry currently faces the challenge of controlling nonequilibrium dynamics such as the dynamic instability of microtubules. In this study, we explored the emergence of dynamic instability through the hybridization of peptide-type supramolecular nanofibers with surfactant micelles. Using real-time confocal imaging, we discovered that the addition of micelles to nanofibers induced the simultaneous but asynchronous growth and shrinkage of nanofibers during which the total number of fibers decreased monotonically. This dynamic phenomenon unexpectedly persisted for 6 days and was driven not by chemical reactions but by noncovalent supramolecular interactions between peptide-type nanofibers and surfactant micelles. This study demonstrates a strategy for inducing autonomous supramolecular dynamics, which will open up possibilities for developing soft materials applicable to biomedicine and soft robotics.

Comparative outcomes of the voltage-dependent current density, charge transportation and rectification ratio of electronic devices fabricated using mechanically flexible supramolecular networks.

In this study, we report the synthetic method of two distinct supramolecular metallogels, namely Mn-BDA and Cd-BDA, using Mn(II) acetate tetrahydrate, Cd(II) acetate dihydrate and butane-1,4-dicarboxylic acid (BDA). DMF, a polar aprotic solvent, was immobilized in both metallogel-networks for their synthesis. The metallogelation of Mn-BDA was successfully attained through the instant mixing of a Mn(II)-source and BDA in DMF solvent media. By applying ultrasonication, a Cd-BDA metallogel was prepared. The stoichiometry of gel-forming components concerning metal salts and the LMWG are accountable to obtain respective stable metallogels. Rheological parameters such as storage modulus (G') and loss modulus (G'') explored the mechanical flexibility of the synthesized metallogels through amplitude and angular frequency sweep experiments. Both the metallogels possess significant mechanical stability, which was determined by monitoring diverse gel-to-sol transition shear strain values (γ%). Distinctive morphological visualizations of both of these metallogels (i.e., Mn-BDA and Cd-BDA) were made via field emission scanning electron microscopic (FESEM) studies, demonstrating a fibrous inter-connected network with a hierarchical self-assembled arrangement for Mn(II)-based metallogels and a typical stacked-flake-like association with hierarchical motifs for Cd(II)-based metallogels. EDAX elemental mapping substantiated the presence of metallogel-forming agents such as individual metal acetate salts, BDA acting as a low-molecular weight gelator, and gel-immobilized solvents such as DMF. Furthermore, Fourier transform infrared spectroscopy and ESI-mass spectroscopy were performed for both these supramolecular metallogels. FT-IR spectroscopic and ESI-mass spectroscopic results clearly substantiate the possible non-covalent supramolecular interactions among basic molecular repeating moieties, i.e., butane-1,4-dicarboxylic acid (the low-molecular weight gelator), individual metal salts and gel-immobilized polar aprotic solvent DMF for the construction of distinct stable supramolecular metallogel-systems. The semiconducting property of the fabricated metallogels was investigated. Two Schottky diodes (SDs) composed of ITO/Cd-BDA/Al and ITO/Mn-BDA/Al in a sandwich pattern with Al serving as the metal electrode were fabricated. Both these metallogel-based devices effectively offer significant semiconducting diode features with non-linear J-V characteristics. The non-ohmic conduction protocol of the fabricated metallogel-based devices was explored. Mn-BDA and Cd-BDA metallogel-based fabricated devices have rectification ratios of 6.67 and 23.50, respectively. The gel-based diode performances were examined by observing the voltage-dependent current density, charge transportation and rectification ratio.

Unusual Ni⋯Ni interaction in Ni(ii) complexes as potential inhibitors for the development of new anti-SARS-CoV-2 Omicron drugs.

Two nickel(ii) coordination complexes [Ni(L)]2(1) and [Ni(L)]n(2) of a tetradentate Schiff base ligand (H2L) derived from 2-hydroxy-1-naphthaldehyde with ethylenediamine were synthesized, designed, and characterized via spectroscopic and single crystal XRD analyses. Both nickel(ii) complexes exhibited unusual Ni⋯Ni interactions and were fully characterized via single-crystal X-ray crystallography. Nickel(ii) complexes [Ni(L)]2(1) and [Ni(L)]n(2) crystallize in monoclinic and triclinic crystal systems with P21/c and P1̄ space groups, respectively, and revealed square planar geometry around each Ni(ii) ion. The structure of both the complexes have established the existence of a new kind of metal system containing nickel(ii)-nickel(ii) interactions with a square planar-like geometry about the nickel(ii) atoms. Both square planar Ni(ii) complexes were often stacked with relatively short Ni⋯Ni distances. The non-bonded Ni-Ni distance (Ni⋯Ni separation) seems to be 3.356 Å and 3.214 Å from the nickel atoms of [Ni(L)]2(1) and [Ni(L)]n(2), respectively. These distances are shorter than the sum of their van der Waals radii (4.80 Å) but longer than the sum of their covalent radii (2.50 Å), indicating that there is a Ni⋯Ni interaction but not a Ni-Ni bond. The discrete molecules are π-stacked and connected via weak intermolecular interactions (C-H⋯O and C-H⋯N). Cyclic voltammetry measurements were obtained for both the complexes, and their pharmacokinetic and chemoinformatics properties were also explored. Detailed structural analysis and non-covalent supramolecular interactions were investigated using single-crystal structure analysis and computational approaches. Both the unique structures show good inhibition performance for the Omicron spike proteins of the SARS CoV-2 virus. To gain insights into potential SARS-CoV-2 Omicron drugs and find inhibitors against the Omicron variants of SARS-CoV-2, we examined the molecular docking of the nickel(ii) complexes [Ni(L)]2(1) and [Ni(L)]n(2) with the SARS-CoV-2 Omicron spike protein (PDB ID: 7WK2 and 7WVO). A strong binding was predicted between Ni(ii) coordination complexes [Ni(L)]2(1) and [Ni(L)]n(2) with the SARS-CoV-2 Omicron variant receptor protein through the negative value of binding affinity. Molecular docking of Nil(ii) complexes [Ni(L)]2(1) and [Ni(L)]n(2) with a DNA duplex (PDB ID: 7D3T) and RNA (PDB ID: 7TDC) binding protein was also studied. Overall, this study suggests that Ni(ii) complexes can be considered as drug candidates against the Omicron variants of SARS-CoV-2.

Phosphorescence resonance energy transfer from purely organic supramolecular assembly.

Phosphorescence energy transfer systems have been applied in encryption, biomedical imaging and chemical sensing. These systems exhibit ultra-large Stokes shifts, high quantum yields and are colour-tuneable with long-wavelength afterglow fluorescence (particularly in the near-infrared) under ambient conditions. This review discusses triplet-to-singlet PRET or triplet-to-singlet-to-singlet cascaded PRET systems based on macrocyclic or assembly-confined purely organic phosphorescence introducing the critical toles of supramolecular noncovalent interactions in the process. These interactions promote intersystem crossing, restricting the motion of phosphors, minimizing non-radiative decay and organizing donor-acceptor pairs in close proximity. We discuss the applications of these systems and focus on the challenges ahead in facilitating their further development.

Solvent-Driven Variations of Third-Order Nonlinear Thermo-Optical Features of Glutaric Acid-Directed Self-Healing Supramolecular Ni(II) Metallogels.

The generation of solvent-directed self-healing supramolecular Ni(II) metallogels of glutaric acid (i.e., Ni-Glu-DMF and Ni-Glu-DMSO) is described in this article. Polar aprotic solvents like N,N'-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) are separately entrapped into the Ni(II)-acetate salt and glutaric acid-mediated networks to attain the semisolid flexible scaffolds. The gel nature of the fabricated materials is experimentally proven through different rheological tests such as amplitude sweep, frequency sweep, and thixotropic (time sweep) measurements. The self-repairing strategy and load-bearing features of the synthesized metallogel are studied in this work. The different supramolecular noncovalent interactions working within the soft scaffold are clearly explored. The formation strategy and the microstructural features of these synthesized metallogels are scrutinized through a Fourier transform infrared (FT-IR) spectroscopy study and field-emission scanning electron microscopy (FESEM) morphological analyses. The FT-IR spectroscopy observation displays a considerable amount of shifting of the infrared (IR) peaks of the xerogel samples of both the metallogels Ni-Glu-DMF and Ni-Glu-DMSO. The electrospray ionization (ESI)-mass spectroscopy result demonstrates the plausible construction of the metallogel network. In order to examine the nonlinear optical characteristics of the two synthesized self-healing metallogels Ni-Glu-DMSO and Ni-Glu-DMF, Z-scan measurements are carried out with a continuous wave (CW) diode-pumped solid-state (DPSS) laser at 532 nm. The nonlinear refractive index, nonlinear absorption coefficient, thermo-optical coefficient, and third-order susceptibility of these metallogels were evaluated by analyzing the experimental data from the Sheik-Bahae formalism. The nonlinear thermo-optical study reveals that these solvent-dependent metallogels show negative signs of nonlinear refractive index and nonlinear absorption coefficient. The figure of merit calculated for these compounds shows good agreement for their use in nonlinear photonic devices.

Spectroscopic studies on the supramolecular interactions of methyl benzoate derivatives with p-sulfocalix[6]arene macrocycles

This paper is a continuation of our previous research and aims to further investigate and elucidate the nature and mechanisms of noncovalent supramolecular interactions between four methyl benzoate derivatives (I-IV), which are capable of exhibiting Twisted Intramolecular Charge Transfer (TICT) and/or Excited State Intramolecular Proton Transfer (ESIPT)‐type behavior, and chemical and biological nanocavities. Photophysical and photochemical properties of molecules I-IV in aqueous solution in the presence of well-recognized macrocyclic host p-sulfocalix[6]arenes (SCA[6]) have been studied using steady-state, time-resolved and 1H NMR spectroscopic techniques. The changes in the ground- and excited-state spectroscopic characteristics (absorption and fluorescence spectra, time-resolved fluorescence spectra, fluorescence decay times and 1H NMR spectra) undergo significant modifications upon encapsulation of the investigated methyl benzoate derivative in the macromolecular cavity. For the two compounds (I and II), the interactions with the macrocycles with a hydrophobic SCA[6] cavity lead to the formation of stable inclusion complexes with 1:1 stoichiometry, both in the ground and excited state, while the stoichiometry of the III-SCA[6] and IV-SCA[6] complexes in the ground and excited states is 1:2. The values of the equilibrium constants have been determined from the spectroscopic data using Benesi-Hildebrand and nonlinear regression procedures. The location of the organic molecule inside the SCA[6] has been investigated by 1H NMR experiments. The changes in macrocyclic compound-induced NMR chemical shifts clearly indicate that the chemical structure of inclusion complexes is very different for methyl benzoate derivative-SCA[6] and methyl benzoate derivative-CB[7] systems. Finally, we have shown, using time-dependent fluorescence Stokes shift, that very fast solvation dynamics of pure water is markedly different from that of the confined water molecule in SCA[6] system.

Non-Covalent Free-Standing Monolayer Nanoarchitectonics of Heterocoronene-Based Discotic Liquid Crystal Molecules

With excellent charge carrier mobility, tendency to form long-range assembly with self-healing ability, and remarkable chemical and mechanical stability, highly conjugated discotic molecules constitute an important class of materials for electronic applications. Here, we report formation of the stable free-standing molecular film of heterocoronene-based discotic liquid crystal (DLC) molecules, held solely by supra-molecular non-covalent interactions. The films of monolayer thickness (∼4 nm) were lifted from Langmuir trough directly onto a circular ring of diameter up to 2 mm as well as onto TEM grids. Films remain free-standing up to a macroscopic length scale, as revealed by optical and secondary electron microscopy, presumably due to the synergistic effect of intermolecular π–π interactions and the dispersion forces between the peripheral alkyl chains as well as their interdigitation. The monolayer is more than 97% transparent in the visible range. Further, resistive switching measurements carried out on the monolayer DLC film transferred on a silver substrate revealed electrochemical metallization to be the governing process. The switching time was found to decrease exponentially with voltage indicating nucleation to be a possible rate-limiting step. We anticipate that the method presented here will facilitate utilization of such non-covalent free-standing films in flexible memristor and nano-electromechanical systems.

Revisiting β-dicyanovinyl substituted calix[4]pyrrole: Toward the chemodosimetric detection of hydrazine in solution

Noticeably, calix[4]pyrrole (C4P) derivatives have usually been employed to recognize charged species or polar guests through non-covalent supramolecular interactions, but the chemodosimetric approach remains scarce in the literature. In this study, the selective chemodosimetric detection and quantification of hydrazine, a hazardous pollutant commonly used in the industry, was performed using UV-spectroscopy with a repurposed β-dicyanovinyl substituted calix[4]pyrrole sensor. The selectivity of the chemodosimeter towards hydrazine was evaluated in acetonitrile with various nucleophiles (nitrogen-containing compounds and a thiol). In addition, the influence of several parameters (time, water content, and temperature) on hydrazine detection by the sensor was evaluated. This study allows for the sensing of hydrazine with a limit of detection (LOD) of 1.3 mg/L, and a linear response in the 10–1000 µM range. The ability to detect hydrazine with the naked eye has also been demonstrated. This paper reports one of the first chemodosimetric approach employed with calix[4]pyrrole to detect and quantify a neutral molecule, namely hydrazine.

Assessment of Fibrin‐Based Hydrogels Containing a Fibrin‐Binding Peptide to Tune Mechanical Properties and Cell Responses

AbstractFibrin‐based hydrogels are used as scaffolds in tissue engineering and regenerative medicine due to their biocompatibility, low cell toxicity, autologous production, and relevance for wound healing and clot formation. The availability of fibrinogen as well as its unique mechanical behavior exhibiting nonlinear elasticity makes it suitable for the fabrication of hydrogels. However, the broad application of fibrin hydrogels in biomaterials still faces challenges in terms of gel shrinkage and degradation processes. This can be addressed through the modulation of the hydrogels'r chemical and mechanical properties. In the present work, it is demonstrated that fibrin‐based hydrogels with adjustable mechanical properties and controllable degradation profiles can be fabricated through the addition of fibrin‐binding peptides. The cyclic peptide X2CXYYGTCLX (Tn7) is used, binding to fibrin by noncovalent supramolecular interactions. These new hydrogels exhibit no toxicity and reduced degradation rate at the same time supporting cell proliferation. Tn7 peptides significantly increase the Young's Modulus and mechanical stiffness as well as fibrin fiber thickness and inter‐fiber crosslinking in hydrogels. In conclusion, hydrogels with optimized mechanical properties and controllable degradation profiles that can be advantageous for further approaches in tissue regeneration, cell‐based therapies, or clinical treatment options are produced.

P-Sulfonato-Calix[4]arene Micelles Stabilize a Povidone Iodine Solution: Supramolecular Interactions, Iodine Retention, and Bactericidal Activity.

Povidone iodine (PVPI) is an antiseptic widely used against a broad spectrum of pathogens. However, undesired side-effects are still associated with PVPI treatment due to the irritant effect of iodine. Reducing the concentration of a PVPI formulation could provide safer and more friendly formulations, for routine use and applications in very delicate organs such as the eye. However, managing the storage of a low-concentration solution of PVPI is challenging due to the high iodine volatility. In this study, we demonstrated that an amphiphilic p-sulfonato-calix[4]arene derivative forming micelles (SC4OC6) improves the stability of a 0.1% PVPI aqueous buffered solution. UV-vis and NMR spectra as well as dynamic and electrophoretic light scattering measurements showed that SC4OC6 establishes non-covalent supramolecular interactions with PVPI, resulting in the formation of nanoaggregates with a negatively charged surface. Isothermal titration calorimetry provided the aggregation parameters and evidenced that the formation of the supramolecular assembly is an enthalpically favored process. The interaction of SC4OC6 with PVPI enhances the iodine retention and stability of the solution without affecting the rapid and effective bactericidal activity of PVPI, as demonstrated by a time-killing assay with Staphylococcus epidermidis.

Formation of Robust and Adaptive Biopolymers via Non-Covalent Supramolecular Interactions.

Biomass-originated materials are the future's next-tier polymers. This work suggests improving mechanical and barrier properties of nature-sourced polymers using non-covalent supramolecular interactions. Polysaccharide chitosan is modified with amino acids via an esterification pathway using a systematic variation of hydrogen bond and aromatic domains (Degrees of substitution 12-49%). These controlled modifications improve stability due to non-covalent interactions, resulting in biopolymers with tailored thermal (decomposition temperature 232-275°C), mechanical (Young's modulus 540-2667MPa), and surface properties (roughness 4-40nm). Chitosan and natural amino acids that are already manufactured at scale are purposely selected. The facile synthesis, controlled properties, stimuli-responsive potential, and inexhaustible origin of the raw materials provide the presented findings with the potential to become the method for the formation of high-performance biodegradable alternatives to petroleum-based polymers that can be used in packaging, food, agriculture, and medicine.

PH assisted modulation in the binding affinity for BODIPY-benzimidazole conjugate with anionic cyclodextrin

Modulation in the properties of chromophoric guest dyes involving non-covalent supramolecular interactions of various macrocyclic hosts are the intense topics of current research. In this study we report interaction of a sulfobutylether-β-cyclodextrin (SBEβCD) host in modulating the photophysical as well as prototropic properties of an inhouse synthesized BODIPY-benzimidazole conjugate dye, abbreviated as BDZ. The SBEβCD host displays substantially different binding strengths for the protonated and unprotonated forms of the prototropic BDZ dye, inducing a large upward pKa shift for the dye. Furthermore, structural confinement of the dye upon binding with the host leads to substantial enhancement in the fluorescence intensity and lifetime for both the prototropic forms of the dye. This can be attributted to the reduction in the non-radiative deexcitation process for the bound dye. Fluorescence enhancements are also accompanied with large increase in fluorescence anisotropy decay times, substantiating dye-host binding. Since unprotonated BDZ in free state is extremely weak in emission due to its intramolecular charge transfer (ICT) character, its fluorescence enhancement on binding to SBEβCD is found to be more pronounced than protonated BDZ. Importantly, emission of BDZ–SBEβCD system appears in the green region of visible spectrum, implying the immense prospect of the system for fluorescence-based sensor and imaging applications in different biological studies.

Preparation of Thermo- and pH-Responsive Microgels Based on Complementary Nucleobase Molecular Recognition.

Complementary interactions between the natural nucleobases is one of the important ways of biomolecular recognition. Although scientists have introduced such supramolecular noncovalent interactions into biomimetic materials through different approaches in recent years, further research is still needed to confer structural features of biomolecules into emerging stimuli-responsive microgels. In this study, a series of bis-thymine end decorated flexible poly (N-isopropyl acrylamide) (T-PNIPAM-T) are obtained through a thymine esterified RAFT agent. Meanwhile, a rigid polymeric backbone poly[1-(4-vinyl benzyl)] adenine (PS A), including several pendant adenines on the side chain is prepared. Through nucleobase complementary pairing subtle supramolecular cross-linked 3D networks are constructed, and further self-assembled to form microgels under the balance between hydrophilicity and block flexibility. More importantly, such supramolecular 3D microgels show volumetric shrinkage in different water content environments and the assembly behavior under thermo and pH stimulated conditions. This exploration is expected to play an important value and significance in the field of biomimetic controlled release of soft matter in the future.

Highly stretchable, elastic, antimicrobial conductive hydrogels with environment-adaptive adhesive property for health monitoring

HypothesisDevelopment of soft conductive materials has enabled the promising future of wearable electronics for motion sensing. However, conventional soft conductive materials typically lack robust adhesive and on-demand removable properties for a target substrate. Therefore, it is believed that the integration of superior mechanical properties, electrical conductivity, and tunable adhesive properties into hydrogels would support and improve their reliable sensing performance. ExperimentsA hydrogel ionic conductor composed of cationic micelles crosslinked in the polyacrylamide (PAM) network was designed and fabricated. The viscoelastic, mechanical, adhesion, electrical, and antimicrobial properties of the hydrogel were systematically characterized. FindingsThe developed ionic conductor possesses a range of desirable properties including mechanical performances such as excellent stretchability (>1100%), toughness, elasticity (recovery from 1000% strain), conductivity (2.72 S·m−1), and antimicrobial property, owing to the multiple non-covalent supramolecular interactions (e.g., hydrogen bonding, hydrophobic, and π-π/cation-π interactions) present in the cross-linked network. Meanwhile, the developed hydrogel is incorporated with different stimuli-responsive polymers and exhibits a tunable adhesive property (triggerable attachment and on-demand removable capabilities) in adapt to the surrounding environmental conditions (i.e., pH, temperature). With all these significant features, the resulting hydrogel ionic conductor serves as a proof-of-concept motion-sensing system with excellent sensitivity and enhanced reliability for the detection of a wide range of motions.

Metal-Organic Frameworks as Unique Platforms to Gain Insight of σ-Hole Interactions for the Removal of Organic Dyes from Aquatic Ecosystems.

The combination of high crystallinity and rich host‐guest chemistry in metal‐organic frameworks (MOFs), have situated them in an advantageous position, with respect to traditional porous materials, to gain insight on specific weak noncovalent supramolecular interactions. In particular, sulfur σ‐hole interactions are known to play a key role in the biological activity of living beings as well as on relevant molecular recognitions processes. However, so far, they have been barely explored. Here, we describe both how the combination of the intrinsic features of MOFs, especially the possibility of using single‐crystal X‐ray crystallography (SCXRD), can be an extremely valuable tool to gain insight on sulfur σ‐hole interactions, and how their rational exploitation can be enormously useful in the efficient removal of harmful organic molecules from aquatic ecosystems. Thus, we have used a MOF, prepared from the amino acid L‐methionine and possessing channels decorated with −CH2CH2SCH3 thioalkyl chains, to remove a family of organic dyes at very low concentrations (10 ppm) from water. This MOF is able to efficiently capture the four dyes in a very fast manner, reaching within five minutes nearly the maximum removal. Remarkably, the crystal structure of the different organic dyes within MOFs channels could be determined by SCXRD. This has enabled us to directly visualize the important role sulfur σ‐hole interactions play on the removal of organic dyes from aqueous solutions, representing one of the first studies on the rational exploitation of σ‐hole interactions for water remediation.

Chiral C2 -symmetric bis-thioureas as enzyme mimics in enantioselective Michael addition.

We report herein the synthesis and application of enantiopure C2 -symmetric primary amine-1,3-bis-thiourea organocatalysts in enantioselective conjugate 1,4-Michael addition of carbonyl containing nucleophiles, to nitroalkenes and N-phenylmaleimide, leading to final products in good enantioselectivities (up to 99%) and yields (up to 99%). We propose supramolecular noncovalent interactions within the organocatalyst's cleft between the substrate and the catalyst, via hydrogen bonding. Supramolecular interaction thus lowers the transition state energy mimicking an enzyme. Mechanism underlying our experimental results is supported by theorical calculations.