Synthesis,characterization and catalytic properties of a copper-containing polyoxovanadate nanocluster in azide–alkyne cycloaddition

A copper-containing polyoxovanadate nanocluster, [(C₂H₅)₄N]₄[V₈Cu₂O₂₄]?2H₂O (1), was synthesized through reaction between the Cu(NO₃)₂?3H₂O and [(C₂H₅)₄N]₄VO₃ in the molar ratio 1?:?4. Nanocluster 1 was characterized by IR, elemental analysis, XRD, SEM, TEM, and X-ray crystallography. The catalytic activity of 1 for the azide–alkyne cycloaddition of different terminal alkynes and organic azides generated in situ from sodium azide and different organic halides was tested. The protocol could afford the corresponding products in good to excellent yield at very low catalyst loadings (3.4 Mol%) under the optimized reaction conditions.     

Synthesis of potential anti-Trypanosoma cruzi azole-naftifine analogues by azide–alkyne click reaction

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Synthesis of bifunctional core–shell particles with a porous zeolite core and a responsive polymeric shell

The aim of our work is the synthesis and characterization of colloidal core–shell particles with a zeolite core and an environmentally responsive shell. We have synthesized colloidal ZSM-5 zeolite and modified the surface with 3-(trimethoxysilyl)propyl methacrylate in order to introduce double bonds at the surface. The cross-linked polymeric shell was prepared by precipitation polymerization using the functionalized zeolite particles as seeds. We employed thermoresponsive poly(N-isopropylacrylamide) and pH-responsive poly(vinylpyridine) as the polymeric shell, respectively. The temperature- and pH-depending swelling and deswelling of the core–shell particles were characterized with dynamic light scattering techniques. Transmission electron microscopy pictures show the morphology of the synthesized particles. It is proposed that these types of bifunctional core–shell particles could be of use for controlled uptake and release applications and separation of molecules.     

Synthesis of polymer–inorganic patchy microcapsules with tunable patches

We introduce a facile and versatile approach for the formation of ball-like polymer–inorganic patchy microcapsules with a tunable shell by combining sol–gel chemistry of silica precursor and phase separation between the polymer and the precursor. Firstly, chloroform-in-water emulsion droplets containing poly(methyl methacrylate) (PMMA), silica precursor [tetraethyl orthosilicate (TEOS)] and co-surfactant sodium dioctyl sulfosuccinate (Aerosol OT or AOT) were prepared by shaking the mixture by hand. Due to the added AOT, water molecules diffuse into the chloroform droplets, and the tiny water droplets would coalesce gradually, triggering the formation of double emulsion droplets. Upon further solvent evaporation, the concentration of the polymer and the silica precursor in the oil shell of the double emulsions increases, leading to the phase separation between the polymer and the precursors (and partially formed silica through the hydrolysis and condensation of TEOS). Because of the confined geometry of the oil shell in the double emulsions, polymeric disc-like structures, stabilized by AOT, were dispersed in the silica precursors. Meanwhile, the silica precursor hydrolyzed and condensed when brought in contact with the aqueous solution, ultimately leading to the formation of a mineralized shell around the polymer domains and the hybrid patchy microcapsules. Effect of synthesis conditions, such as the amount of TEOS, AOT, and PMMA used, the pH value, and solvent evaporation rate on interfacial behavior of the solvent/water; and the morphology of the patchy microcapsules were investigated. Patchy microcapsules with tunable patch size and shape can be generated through tailoring the experimental parameters. Our study indicates that the hybrid patchy microcapsules can be formed by taking advantage of the sol–gel chemistry and the phase separation process, and the underlying generality of the synthesis procedure allows for a variety of applications, including drug storage, coatings, delivery, catalysis, and smart building blocks in self-assembling systems.     

Orthogonal functionalization of a fullerene building block through copper-catalyzed alkyne–azide and thiol–maleimide click reactions

In this study, the synthesis of an orthogonally clickable fullerene building block mono-adduct bearing on one side an alkyne unit and a maleimide moiety on the other side is presented. This derivative has been involved in CuAAC and thiol–maleimide click reactions using stepwise or one-pot processes with benzyl azide and 1-octanethiol. The one-pot process involving the CuAAC reaction followed by the thiol–maleimide conjugation gives the highest yield. This new platform could pave the way for the synthesis of a wide range of fullerene derivatives exploiting this set of orthogonal reactions.     

A simple protocol for the synthesis of triazole-linked cyclic glycopeptidomimetics: a sequential Ugi-MCR and azide–alkyne cycloaddition approach

Sequential combination of Ugi-MCR and click chemistry has been employed for the synthesis of triazole linked cyclic glycopeptidomimetics. The protocol employs Poc-amino alkyl isonitriles, sugar-1-amines, azido acids, and simple aldehydes as precursors. The dual nature of the propargyloxycarbonyl (Poc) group was explored for amine protection as well as cycloaddition with an azide. All the cyclic glycopeptidomimetics are isolated and characterized.     

Fabrication of core/shell hybrid organic–inorganic polymer microspheres via Pickering emulsion polymerization using laponite nanoparticles

Oil-in-water (o/w) emulsions of styrene, as monomer oil in water, were achieved successfully via Pickering emulsification with laponite nanoparticles as the sole inorganic stabilizers. The formed emulsions showed excellent stability not only against droplets coalescence (before polymerization) but also against microparticles coagulation (after polymerization). Generally, the number of composite polystyrene microparticles (PS) increased and their sizes decreased with the content of solid nanoparticles used in stabilizing the precursor o/w emulsions. This is consistent with the formation of rigid layer(s) of the inorganic nanoparticles around the PS microparticles thus a better stability was achieved. The composite microparticles were characterized using various techniques such as surface charge, stability, transmission electron microscope (TEM), scanning electron microscope (SEM) and Fourier transform infra-red (FT-IR). Coating films of the prepared latexes were applied to flat glass surfaces and showed reasonable adhesion compared to PS latex particles prepared with conventional surfactants. The effect of employed conditions on the features of the resulting emulsions in terms of stability and particle size has been discussed.     

Preparation of biodegradable and thermoresponsive enzyme–polymer conjugates with controllable bioactivity via RAFT polymerization

The preparation of biodegradable and thermoresponsive enzyme–polymer bioconjugates with controllable enzymatic activity via reversible addition−fragmentation chain transfer (RAFT) polymerization and amidation conjugation reaction is presented. A new 2-mercaptothiazoline ester functionalized RAFT agent with intra-disulfide linkage was synthesized and used as chain transfer agent (CTA) to generate a biocompatible homopolymer, poly(ethyleneglycol) acrylate (polyPEG-A) and a thermoresponsive copolymer of poly(ethyleneglycol) acrylate with di(ethyleneglycol)ethyl ether acrylate [poly(PEG-A-co-DEG-A)]. These biodegradable and thermoresponsive polymers were then conjugated to the surface of glucose oxidase (GOx) under mild condition to afford the biodegradable and thermoresponsive enzyme–polymer conjugates. Cleavage of the polymer chains from the GOx surface obviously recovered the enzymatic activity. The thermoresponsive test of GOx-poly(PEG-A-co-DEG-A) revealed that the bioconjugate exhibited regular enzymatic activity fluctuation upon the temperature change below or above the lower critical solution temperature (LCST). The as-prepared enzyme–polymer conjugates were also characterized using ¹H NMR, UV–vis spectroscopy, polyacrylamide gel electrophoresis (PAGE) and biocatalytic activity tests. These smart enzyme–polymer conjugates would envision promising applications in biotechnology and biomedicine.     

Physical–chemical study of water in contact with a hydrophilic polymer: Nafion

The study detailed in this paper is about the determination of the physical–chemical parameters of water, after keeping it in prolonged contact with the Nafion polymer. The parameters under study are: electrical conductivity, χ (μS cm^?1); heat of mixing with acid (HCl), ΔQ _mix ^HCl (J kg^?1) or basic (NaOH) solutions, ΔQ _mix ^NaOH  (J kg^?1), and pH. χ increases of up to two orders of magnitude, ΔQ _mix ^NaOH  (J kg^?1) is exothermic and increases as the electrical conductivity increases, with a roughly linear trend, up to one order of magnitude. The analogous ΔQ _mix ^HCl  (J kg^?1), on the contrary, is found to be null. The pH is quite acid and shows a very good linear correlation with log χ. The linear correlations hint at a single cause for the variation of the three very different physical–chemical parameters. This complex and hard to rationalize phenomenology, finds a good theoretical support in the work hypothesis of the formation of dissipative structures within the liquid. These are far-from-equilibrium systems outside the paradigm of classical thermodynamics. The work hypothesis of the formation of molecular aggregates of water molecules (dissipative structures, aqueous nanostructures, clusters, coherence domains, etc.) is shared with two other aqueous systems obtained with different preparation protocols, so we briefly recall them here: (1) EDS (extremely diluted solutions): obtained through an iterative process of successive dilutions and agitations. (2) IFW (iteratively filtered water): obtained through an iterative process of successive filtrations through sintered glass filters. (3) INW (iteratively nafionized water): obtained through an iterative process of successive drying and wetting of the Nafion polymer. Each protocol produces water exhibiting its own peculiarities, to the point that they can be considered different, albeit with the common element of a variation of the super-molecular structure of the water solvent. The physical–chemical properties of these perturbed waters cannot be framed by the paradigm of classical thermodynamics, but rather require the use of the thermodynamics of systems far from the equilibrium and of irreversible processes.     

Controlled preparation of core–shell polystyrene/polypyrrole nanocomposite particles by a swelling–diffusion–interfacial polymerization method

Polystyrene/polypyrrole (PS/PPy) core–shell nanocomposite particles with uniform and tailored morphology have been successfully synthesized using the “naked” PS particulate substrate with the aid of a proposed strategy, the so-called swelling–diffusion–interfacial polymerization method. After initially forming pyrrole-swollen PS particles, diffusion of the monomer toward the aqueous phase was controlled through the addition of hydrochloric acid, eventually leading to its polymerization on the substrate particle surface. This process allows the nanocomposite particles to possess uniform and intact PPy overlayer and affords much more effective control over the structure and morphology of the resultant nanocomposites by simply changing the PS/pyrrole weight ratio or the addition amount of the doping acid. In particular, the nanocomposite particles with a thin, uniform, and intact PPy overlayer and their corresponding PPy hollow particles were obtained at a low addition amount of pyrrole. The resultant nanocomposite particles have been extensively characterized using scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, and thermogravimetry.     

Synthesis of core–shell magnetic ion-imprinted polymer nanospheres for selective solid-phase extraction of Pb2+ from biological,food, and wastewater samples

Magnetic ion-imprinted polymer nanospheres, which have core–shell structures, have been synthesized as an adsorbent for extraction of Pb²⁺ from real samples prior to its flame atomic absorption spectrometric determination. The prepared adsorbent has been characterized using XRD, VSM, TEM, and FTIR measurements. The optimization results revealed that the adsorbent exhibited high selectivity toward Pb²⁺ over other cations such as Cu²⁺ and Zn²⁺. In addition, the removal efficiency of synthesized adsorbent was considerable (q_m?=?171.42?mg g^?1), its calibration curve was linear (0.5?850.0?ng mL^?1), and detection limit was 0.01?ng mL^?1. These results suggested that the prepared nanoadsorbent is an ideal candidate for solid-phase extraction of Pb²⁺ ions.     

Preparation of core–shell composite polymer particles by a novel heterocoagulation based on hydrophobic interaction

Submicron-sized cationic polystyrene shell particles with active ester groups were effectively self-assembled on hydrophobic surfaces of cross-linked polystyrene (PST) particles, uncharged core particles with ca. 8.5-µm diameter in aqueous systems. The hydrophobic interactions between the shell particles and core particles play a key role in heterocoagulation. The resulting heterocoagulates were highly physically stable in water, and the morphology was controlled by several factors including the solid content of latex, self-assembling time, and electrolyte concentration. Composite polymer particles with a core–shell structure were successfully obtained from the heterocoagulates by heat treatment for 3 h at a temperature above the glass transition temperature (T_g) of the cationic polymer shell particles.     

Synthesis of core-shell structured polymers with inserted thioether from a multi-functional scaffold

The synthesis of a thioether inserted, core-shell structured polymer from the scaffold of hyperbranched polyglycerol (PG) was described. PG was first allyl functionalized, and in the presence of AIBN, the allyl groups further underwent radical addition to thiol compounds, thus thiol functional polyethylene oxide monomether (MPEO) were grafted onto PG. Similarly, 2-mercaptoethy-lammonium chloride was introduced onto PG via thiol addition, and the residual amino groups were further quaternized with decyl bromide, leading to an amphiphilic core-shell structure polymer.     

Synthesis,characterization and luminescence properties of a coordination polymer based on self-assembly of PrIII with inorganic–organic hybrid bridging ligands

A new coordination polymer having the formula [Pr(μ ₅-S₂O₃)(μ ₄-tp)_0.5(H₂O)] _n (1) (S₂O₃ = thiosulfate dianion; tp = terephthalate dianions) was obtained by in situ reaction of Pr₂(SO₄)₃ · 6H₂O with H₂tp ligands under solvothermal conditions (H₂O/ethanol). The coordination polymer obtained was characterized by elemental analysis, FT-IR, thermogravimetry (TG), fluorescent spectra and single crystal X-ray diffraction analysis. The most intriguing structural feature is that the complex exhibits a 3D open framework resulting from bridge-linking coordination between ligands and praseodymium ions. Additionally, 1 has characteristic emission spectra of Pr^III with good fluorescence properties. This is the first coordination polymer based on thiosulfate/terephthalate ligands and a rare earth metal and has an unprecedented pentadentate-bridge-linking coordination mode of the thiosulfate group.     

Synthesis of bifunctional peptide derivatives based on a β-cyclodextrin core with drug delivery potential

A selective, versatile, robust methodology for bifunctionalization of β-cyclodextrin is achieved allowing the attachment of peptides in varying C- and/or N-terminal combinations on resin using Fmoc SPPS. Two linkers are attached to cyclodextrin enabling selective binding to the resin (or a peptide attached to the resin). Continuation of peptide growth and/or cleavage from the resin follows, thus various combinations of peptide-cyclodextrin species are achieved. A model peptide (Gly-Ala) is used in this study to illustrate the potential of this system for attaching one or more bioactive peptides for drug transport and release purposes.     

Biomimetic synthesis of raspberry-like hybrid polymer–silica core–shell nanoparticles by templating colloidal particles with hairy polyamine shell

The nanoparticles composed of polystyrene core and poly[2-(diethylamino)ethyl methacrylate] (PDEA) hairy shell were used as colloidal templates for in situ silica mineralization, allowing the well-controlled synthesis of hybrid silica core–shell nanoparticles with raspberry-like morphology and hollow silica nanoparticles by subsequent calcination. Silica deposition was performed by simply stirring a mixture of the polymeric core–shell particles in isopropanol, tetramethyl orthosilicate (TMOS) and water at 25 °C for 2.5 h. No experimental evidence was found for nontemplated silica formation, which indicated that silica deposition occurred exclusively in the PDEA shell and formed PDEA–silica hybrid shell. The resulting hybrid silica core–shell particles were characterized by transmission electron microscopy (TEM), thermogravimetry, aqueous electrophoresis, and X-ray photoelectron spectroscopy. TEM studies indicated that the hybrid particles have well-defined core–shell structure with raspberry morphology after silica deposition. We found that the surface nanostructure of hybrid nanoparticles and the composition distribution of PDEA–silica hybrid shell could be well controlled by adjusting the silicification conditions. These new hybrid core–shell nanoparticles and hollow silica nanoparticles would have potential applications for high-performance coatings, encapsulation and delivery of active organic molecules.     

Synthesis of linear unsubstituted poly(4,4′-triphenylamine) via Suzuki-Miyaura coupling of an asymmetric AB monomer

Polytriarylamines (PTAAs) are amorphous polymers that can be reversibly oxidized to generate stable radical cations. Despite exhibiting a low charge carrier mobility, PTAAs are widely used as hole-transporting layers in perovskite solar cells due to their excellent stability under ambient conditions. The highest occupied molecular orbital (HOMO) energy levels of PTAA are generally in the range of −5.1 to −5.2 eV, and therefore slightly too high for an optimal alignment with perovskites. Most linear PTAAs carry two or three methyl substituents per repeating unit. While these prevent crosslinking of chains and thus provide reaction control, the electron-donating substituents raise the energy level of the HOMO. Unsubstituted PTAA on the other hand is usually obtained crosslinked via oxidative polymerization, while nickel-catalyzed Grignard polycondensation leads to inclusion of impurities. We report the synthesis of linear unsubstituted PTAA using Suzuki-Miyaura coupling of a novel asymmetric monomer, 4-((4-bromophenyl)(phenyl)amino)phenyl)boronic acid M1 . Based on matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF) and ¹H NMR analysis, we can conclude that the hydrogen-terminated linear polymer is obtained. The determined HOMO energy level of −5.47 eV is a favorable match for many perovskite systems.     

Molecular designing and DFT investigation of novel alternating donor–acceptor dibenzo[b,d]thiophen-based systems: from monomer to polymer

The structures and properties of dibenzo[b,d]thiophene (DBT) based alternating donor–acceptor conjugated oligomers, in which thieno[3,4-b]pyrazine (TP), thieno[3,4-b]thiadiazole (TD), and [1,2,5]thiadiazolo[3,4-e]thieno[3,4-b]pyrazine (TTP) as acceptors, and their periodic polymers were investigated by the density function theory (DFT) at the B3LYP/6-31G(d) level. The bond length, electron density at bond critical points (BCPs) and nucleus-independent chemical shift (NICS) are analyzed and correlated with the conductive properties. NICS shows that the conjugation degree is increased with main chain extension. Research results show the conductive ability of compounds with 1:2 D–A ratio is better than that with 1:1 D–A ratio. The reorganization energies and energy bands also are considered. The results suggest that (BTDDBT) _n and (BTPDDBT) _n have small reorganization energy (0.163 and 0.152 eV, respectively) and quite low energy gap (0.73 and 0.56 eV, respectively), which indicate that they may be potential organic conductive materials.     

Nanocrystalline hydroxyapatite powders by a chitosan–polymer complex solution route: Synthesis and characterization

Nanocrystalline hydroxyapatite (HAp) powders were successfully synthesized by a simple method using chitosan–polymer complex solution. To obtain HAp nanopowders, the prepared precursor was calcined in air at 400–800 °C for 2 h. The phase composition of the calcined samples was studied by X-ray diffraction (XRD) technique. The XRD results confirmed the formation of HAp phase with a small trace of monotite phase. With increasing calcination temperature, the crystallinity of the HAp increased, showing the hexagonal structure of HAp with the lattice parameter a in a range of 0.94030–0.94308 nm and c of 0.68817–0.68948 nm. The particle sizes of the powder were found to be 55.02–73.36 nm as evaluated by the XRD line broadening method. The chemical composition of the calcined powders was characterized by FTIR spectroscopy. The peaks of the phosphate carbonate and hydroxyl vibration modes were observed in the FTIR spectra for all the calcined powders. TEM investigation revealed that the prepared HAP samples consisted of rod-like nanoparticles having the particle size in the range of 100–300 nm. The corresponding selected-area electron diffraction (SAED) analysis further confirmed the formation of hexagonal structure of HAp.     

Antihyperglycaemic mechanisms of an aceteoside polymer from rose flowers and a polysaccharide–protein complex from abalone mushroom

Oral administration of an aceteoside polymer from rose Rosa rugosa (P_1-b) and a polysaccharide–peptide complex from abalone mushroom Pleurotus abalonus (LB-1b), both with antioxidant activity, produced antihyperglycaemic effects in alloxan-induced diabetic mice. The expression of insulin, superoxide dismutase and pancreas duodenum homeobox factor-1 essential for pancreatic islet function as estimated by real-time PCR was augmented. The reactive oxygen species-scavenging ability of the rose constituent was notably stronger than the mushroom constituent. Thus, the two biomolecules protected the pancreas from oxidative stress, elevated pancreatic insulin expression and lowered circulating glucose level.