Poly 4-vinylpyridine Research Articles

Magnetic bentonite decorated with Pd nanoparticles and cross-linked polyvinyl pyridine as an efficient nanocatalyst for Suzuki coupling and 4-Nitrophenol reduction reactions

This study reports the preparation of a novel type of support based on magnetically recyclable bentonite functionalized with divinylbenzene-polyvinyl pyridine (PVP-DVB) for Pd (II) nanocatalyst by a simple cost-effective method. Firstly, the conventional co-precipitation method synthesized Fe3O4 nanoparticles (NPs) onto bentonite sheets. Then the prepared magnetic support surface was functionalized by divinylbenzene-polyvinyl pyridine (PVP-DVB) to create a cross-linked polymer with a high coordination ability with palladium. Repeated nitrogen units in the PVP-DVB polymer chain increase the number of Pd bonds and thus lead to higher performance of the nanocatalyst. Finally, the palladium NPs were simultaneously synthesized and immobilized under mild conditions. The synthesized nanocatalyst was characterized by several methods such as scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, Fourier-transform infrared spectroscopy, vibrating sample magnetometer, inductively coupled plasma mass spectrometry and thermogravimetric analysis. The efficiency of synthesized heterogeneous nanocatalyst was investigated in Suzuki–Miyaura cross-coupling reactions between a range of aryl halides (X = Cl, Br, I) with phenylboronic acid and in the reduction of 4-nitrophenol (4-NP). Moreover, the synthesized nanocatalyst could be easily recovered and reused several times with an efficiency greater than 90%.

PH-Responsive Carbon Foams with Switchable Wettability Made from Larch Sawdust for Oil Recovery.

The global challenge of oil pollution calls for the efficient selective recovery of oil or organics from oil-water mixtures. A pH-responsive carbon foam (CF) made from liquefied larch sawdust (LLS) with switchable wettability was fabricated in this work. After grafted with poly 4-vinyl pyridine (P4vp), the CF obtained a switchable wettability surface, which allowed the CF to exhibit superhydrophilicity and superhydrophobicity at different pH levels, respectively. The results revealed that the pH-responsive CF possessed a three-dimensional (3D) spongy-like skeleton and porous structure with a diameter between 50 and 200 µm. Thus, the pH-responsive CF could absorb 15-35 g/g of oil/organics in a neutral aqueous solution at pH = 7 and desorb all the absorbate within 40 s after immersion in an aqueous solution at pH = 1. Moreover, only about 2.8% loss was observed for organic (chloroform) absorption and recovery after reusing up to 15 cycles, which indicated promising prospects in oil and organic recovery.

Semi-Interpenetrating Polymer Networks Based on Hydroxy-Ethyl Methacrylate and Poly(4-vinylpyridine)/Polybetaines, as Supports for Sorption and Release of Tetracycline.

Semi-interpenetrating polymer networks (semi-IPN) represent a type of polymeric material that has gained increasing amount of interest for their potential biomedical application. This study presents the synthesis, characterization and tetracycline loading/release capacities of semi-IPNs based on hydroxyethyl methacrylate (HEMA) and poly(4-vinylpyridine) (P4VP) or poly (1-vinyl-4-(1-carboxymethyl) pyridinium betaine) (P4VPB-1) and poly (1-vinyl-4-(2-carboxyethyl) pyridinium betaine) (P4VPB-2). The optimization of the semi-IPNs synthesis was achieved by studying the influence of reaction parameters (chemical structure of the cross-linking agent, HEMA:crosslinker ratio, HEMA:linear polymers ratio and the type of solvent of the linear polymers) on the yield of obtaining semi-IPNs and swelling capacity of these systems. Fourier-transform infrared analysis and scanning electron microscopy highlighted the chemical structures and morphologies of the semi-IPNs. The higher swelling capacity was observed in the case of the PHEMA/P4VPB-2 network due to the increased hydrophilicity of P4VPB-2 compared with P4VP and P4VPB-1 polymers. In vitro release studies of tetracycline reveal that the release mechanism is represented by non-Fickian diffusion being controlled by both diffusion and swelling processes. The antimicrobial activity of semi-IPN-tetracycline systems was tested against E. coli and S. aureus, demonstrating that tetracycline is released from the semi-IPN and retains its bactericidal activity. An increased value of the inhibition zone diameter compared with that of tetracycline indicates the possibility that the semi-IPN containing P4VPB-2 also exhibits intrinsic antimicrobial activity due to the presence of the polybetaine in the network structure.

Stimuli-Responsive Triblock Terpolymer Conversion into Multi-Stimuli-Responsive Micelles with Dynamic Covalent Bonds for Drug Delivery through a Quick and Controllable Post-Polymerization Reaction

Stimuli-responsive copolymers are of great interest for targeted drug delivery. This study reports on a controllable post-polymerization quaternization with 2-bromomethyl-4-fluorophenylboronic acid of the poly(4-vinyl pyridine) (P4VP) block of a common poly(styrene)-b-poly(4-vinyl pyridine)-b-poly(ethylene oxide) (SVE) triblock terpolymer in order to achieve a selective responsivity to various diols. For this purpose, a reproducible method was established for P4VP block quaternization at a defined ratio, confirming the reaction yield by 11B, 1H NMR. Then, a reproducible self-assembly protocol is designed for preparing stable micelles from functionalized stimuli-responsive triblock terpolymers, which are characterized by light scattering and by cryogenic transmission electron microscopy. In addition, UV-Vis spectroscopy is used to monitor the boron-ester bonding and hydrolysis with alizarin as a model drug and to study encapsulation and release of this drug, induced by sensing with three geminal diols: fructose, galactose and ascorbic acid. The obtained results show that only the latter, with the vicinal diol group on sp2-hybridized carbons, was efficient for alizarin release. Therefore, the post-polymerization method for triblock terpolymer functionalization presented in this study allows for preparation of specific stimuli-responsive systems with a high potential for targeted drug delivery, especially for cancer treatment.

Steric hindrance affects interactions of poly(styrene–alt–DMHPMI) copolymer with strongly hydrogen-bond-accepting homopolymers

In this study, we synthesized the monomer N-(2,6-dimethylhydroxyphenyl)maleimide (DMHPMI) in three steps from 2,6-dimethylphenol and then reacted it with styrene through free radical copolymerization to prepare the alternating copolymer poly(styrene–alt–dimethylhydroxyphenylmaleimide) [poly(S–alt–DMHPMI)]. We used Fourier transform infrared (FTIR) spectroscopy, 1H and 13C nuclear magnetic resonance (NMR) spectroscopy, and mass-analyzed laser desorption ionization/time-of-flight (MALDI-TOF) mass spectrometry to confirm its structure. Differential scanning calorimetry revealed that blends of the alternating copolymers poly(S–alt–DMHPMI) and poly(styrene–alt–(para–hydroxyphenylmaleimide)) [poly(S–alt–pHPMI)] with the Strongly Hydrogen-Bond-Accepting homopolymers poly(4-vinylpyridine) (P4VP) and polyvinylpyrrolidone (PVP) each exhibited single-value glass transition temperatures (Tg) over the entire compositional range, indicative of full miscibility. Nevertheless, a negative deviation from the linear rule occurred for the Tg behavior of the PS–alt–PHPMI/P4VP blends, due to the weak acidity of the HPMI units, while the intermolecular interactions of the PS–alt–PHPMI coplymers were also inhibited because of strong self-association of the PHPMI units. FTIR spectral analyses of the ratio of hydrogen-bonded OH and pyridyl groups confirmed this behavior. In contrast, slightly positive deviations from the linear rule occurred for the Tg behavior when blending poly(S–alt–DMHPMI) or poly(S–alt–pHPMI) with the PVP homopolymer; here, the intermolecular interactions of the poly(S–alt–DMHPMI)/PVP blends were weaker than those of the poly(S–alt–pHPMI)/PVP blends, due to the steric hindrance of the DMHPMI units being greater than that of the pHPMI units.

Biological properties of chitosan/Eudragit E 100 and chitosan/poly(4-vinylpyridine) coatings electrophoretically deposited on AgNPs-decorated titanium substrate

The objective of the study was the determination of the response, in contact with human osteoblast-like MG-63 cells, of electrophoretically deposited coatings composed of chitosan (CS), Eudragit E 100 (EE100), or poly(4-vinylpyridine) (P4VP) on a silver nanoparticle (AgNPs)-decorated titanium substrate. Before deposition, the substrate was coated with silver by electro-reduction of silver nitrate. The coatings deposition was carried out in suspensions containing 0.1 % (w/w) of one of the biopolymers, EE100 or P4VP, with 0.1 % (w/w) of CS for 10 V and 1 min. Biopolymer coatings were successfully deposited while maintaining high uniformity. The deposited silver did not cause cytotoxicity. The biological study revealed that when compared to CS/P4VP, CS/EE100 coating performed better and showed a decrease in MG-63 cell viability only after three days of testing.

Cycloaddition of CO2 to Epichlorohydrin over Pyridine, Vinylpyridine, and Poly(vinylpyridine): The Influence of Steric Crowding on the Reaction Mechanism

The cycloaddition of CO2 with epoxides is a 100% atom economical reaction that utilizes CO2 and produces valuable cyclic carbonate products. Organic bases are attractive catalysts for this reaction because of their green characteristics, such as low cost and low toxicity. However, further catalyst development is required to achieve acceptable yields at mild temperatures and pressures. This work aims to establish catalyst structure–performance relationships to accelerate the rational design of high performance organic base catalysts for the cycloaddition reaction. Toward this end, we investigate the influence of steric crowding at the ring nitrogen atom of a series of pyridine-based catalysts on the reaction mechanism and catalyst performance using batch reactor measurements at a mild temperature (57 °C) and atmospheric pressure under solventless conditions combined with in situ infrared spectroscopic characterization of the catalysts. We show that steric crowding at the ring nitrogen atom has a significant influence on the reaction mechanism and catalyst performance. Catalysts with unhindered access to the ring nitrogen atom, such as pyridine, 4-vinylpyridine, 3-vinylpyridine, and poly(4-vinylpyridine), are completely transformed during the cycloaddition reaction by quaternization from the epoxide reactant, producing zwitterionic pyridinium-epoxide adducts and ammonium salts that precipitate out of solution. Catalysts with hindered access to the ring nitrogen atom, such as 2-vinylpyridine and poly(2-vinylpyridine), resist quaternization from the epoxide reactant due to the high degree of steric hindrance at the ring nitrogen atom. The poly(2-vinylpyridine) catalyst in particular displayed high stability, high product selectivity, and high activity for cyclic carbonate synthesis. These molecular-level insights have significant implications for the rational design of active, stable, and metal-free catalysts for cyclic carbonate synthesis by tuning the steric crowding at the active site.

Adsorption Properties of Magnetic CoFe2O4@SiO2 Decorated with P4VP Applied to Bisphenol A

In this study, the preparation and adsorption properties of cobalt ferrite core-shell nanoparticles coated with silica and decorated with poly(4-vinylpyridine) (CoFe2O4@SiO2-P4VP) applied to bisphenol A (BPA) adsorption were described. The CoFe2O4-based core was coated by a nanometric layer of silica under Stöber conditions and followed by coating with poly(4-vinylpyridine) via surface polymerization in miniemulsion. The characterizations involved transmission electron microscopy (TEM), X-ray diffraction (XRD), vibrating sample magnetometer (VSM), Fourier transform infrared (FTIR), thermogravimetry (TGA), dynamic light scattering (DLS) and zeta potential. The polymeric core-shell nanoparticle showed a spherical structure with a magnetic core of ca. 11 nm and a layer of silica of ca. 4 nm. The amount of poly(4-vinylpyridine) that decorated the nanoparticle surface was verified by thermogravimetric analysis. CoFe2O4@SiO2-P4VP exhibited the capacity to adsorb bisphenol A. The chemometric model indicated a significant effect between the ionic strength and pH of the solution in the adsorption of bisphenol A. CoFe2O4@SiO2-P4VP presented a superior adsorption capacity towards BPA (46.6 mg g−1) in optimized conditions. The adsorption kinetics of BPA by CoFe2O4@SiO2-P4VP involved a pseudo-second order process. Also, the adsorption isotherm indicated a multilayer process with data well-adjusted by Freundlich equation. The nanomaterial CoFe2O4@SiO2-P4VP can be reused in adsorption of BPA for up to eight cycles.

Construction of micelles and hollow spheres via the self-assembly behavior of poly(styrene-alt-pHPMI) copolymers with poly(4-vinylpyridine) derivatives mediated by hydrogen bonding interactions.

This study describes the preparation of hydrogen bonding connected micelles, consisting of a poly(styrene-alt-(para-hydroxyphenylmaleimide)) [poly(S-alt-pHPMI)] core and a poly(4-vinylpyridine) (P4VP) derivative shell in a selective solvent. The aim was to modify hydrogen bonding interaction sites at the core/shell interface by synthesizing P4VP derivatives in three different sequences, namely, P4VP homopolymers, PS-co-P4VP random copolymers, and block copolymers. TEM images showed the successful self-assembly of poly(S-alt-pHPMI)/PS-co-P4VP inter-polymer complexes into spherical structures. To dissolve the core structures, 1,4-dibromobutane was used as a cross-linking agent to tighten the PS-co-P4VP shell. The morphologies, particle sizes, hydrogen bonding, cross-linking reaction, and core dissolution were confirmed by TEM, DLS, FTIR, and AFM analyses. Poly(S-alt-pHPMI)/PS41-r-P4VP59 hydrogen bonding connected micelles, cross-linked micelles, and hollow spheres were larger and more irregular than poly(S-alt-pHPMI)/P4VP inter-polymer complexes due to the random copolymer architecture and the decrease in intermolecular hydrogen bonds. However, poly(S-alt-pHPMI)/PS68-b-P4VP32 resulted in rod- or worm-like structures after core dissolution.

Facile synthesis of porous transition metal hydroxides from a poly(4-vinyl pyridine) film by controlling pH.

Non-noble transition metal hydroxides have been widely used in electrochemical devices because of low cost and multiple redox states. In particular, self-supported porous transition metal hydroxides are used to improve the electrical conductivity, as well as achieving fast electron and mass transfer and a large effective surface area. Herein, we introduce facile synthesis of self-supported porous transition metal hydroxides using a poly(4-vinyl pyridine) (P4VP) film. We used metal cyanide as a transition metal precursor capable of forming metal hydroxide anions in aqueous solution, which is the seed for transition metal hydroxides. To increase the coordination between P4VP and the transition metal cyanide precursors, we dissolved the precursors in buffer solutions with various pH. When the P4VP film was immersed in the precursor solution with lower pH, the metal cyanide precursors were sufficiently coordinated with the protonated nitrogen in P4VP. When reactive ion etching was performed on the precursor-containing P4VP film, the P4VP region without coordination was etched out and became pores. Then, the coordinated precursors were aggregated as metal hydroxide seeds and became the metal hydroxide backbone, resulting in the formation of porous transition metal hydroxide structures. We successfully fabricated various self-supported porous transition metal hydroxides (Ni(OH)2, Co(OH)2, and FeOOH). Finally, we prepared a pseudo-capacitor based on self-supported porous Ni(OH)2, which showed a good specific capacitance (780 F g-1 at 5 A g-1).

Stabilizing oil-oil interfaces with mixed-shell polymeric nanoparticles prepared via PISA and the grafting combination.

The preparation of mixed-shell polymeric nanoparticles (MSPNs) and their stabilized non-aqueous Pickering emulsions was described in this study. Poly(methyl methacrylate)-poly(4-vinylpyridine) (PMMA-P4VP) diblock copolymer nanoparticles with different morphologies including spheres, worms and vesicles were first prepared via reversible addition-fragmentation chain transfer-based polymerization induced self-assembly in toluene. C18 alkyl chains were subsequently grafted onto the surfaces of the as-prepared PMMA-P4VP nanoparticles, affording C18/PMMA-P4VP MSPNs with P4VP blocks as the core and C18/PMMA chains as the mixed shells. MSPNs were utilized as Pickering emulsifiers to prepare non-aqueous Pickering emulsions, where [Bmim][PF6] and toluene oils were selected. Two kinds of different Pickering emulsions, [Bmim][PF6]-in-toluene and toluene-in-[Bmim][PF6], could be formed, depending on the initial location of MSPNs. However, neither of them could be generated when PMMA-P4VP diblock copolymer nanoparticles were adopted as Pickering emulsifiers, indicating MSPNs were better than diblock copolymer nanoparticle precursors in the aspect of stabilizing oil-oil interfaces. The formation mechanisms of different kinds of Pickering emulsions were unraveled in this study.

Hydrophobically modified complex coacervates for designing aqueous pressure-sensitive adhesives.

The rheology of complex coacervates can be elegantly tuned via the design and control of specific non-covalent hydrophobic interactions between the complexed polymer chains. The well-controlled balance between elasticity and energy dissipation makes complex coacervates perfect candidates for pressure-sensitive adhesives (PSAs). In this work, the polyanion poly(3-sulfopropyl methacrylate) (PSPMA) and the polycation quaternized poly(4-vinylpyridine) (QP4VP) were used to prepare complex coacervates in water. Progressive increase of hydrophobicity is introduced to the polyanion via partial deprotection of the protected precursor. Hence, the polymer chains in the complex coacervates can interact via both electrostatic (controlled by the amount of salt) and hydrophobic (controlled by the deprotection degree) interactions. It was observed that: (i) a rheological time-salt-hydrophobicity superposition principle is applicable, and can be used as a predictive tool for rheology, (ii) the slowdown of the stress relaxation dynamics, due to the increase of hydrophobic stickers (lower deprotection degree), can be captured by the sticky-Rouse model, and (iii) the systematic variation of hydrophobic stickers, amount of salt, and molecular weight of the polymers, enables the identification of optimizing parameters to design aqueous PSA systems. The presented results offer new pathways to control the rheology of complex coacervates and their applicability as PSAs.

Continuous flow synthesis of pyridinium salts accelerated by multi-objective Bayesian optimization with active learning.

We report a human-in-the-loop implementation of the multi-objective experimental design via a Bayesian optimization platform (EDBO+) towards the optimization of butylpyridinium bromide synthesis under continuous flow conditions. The algorithm simultaneously optimized reaction yield and production rate (or space-time yield) and generated a well defined Pareto front. The versatility of EDBO+ was demonstrated by expanding the reaction space mid-campaign by increasing the upper temperature limit. Incorporation of continuous flow techniques enabled improved control over reaction parameters compared to common batch chemistry processes, while providing a route towards future automated syntheses and improved scalability. To that end, we applied the open-source Python module, nmrglue, for semi-automated nuclear magnetic resonance (NMR) spectroscopy analysis, and compared the acquired outputs against those obtained through manual processing methods from spectra collected on both low-field (60 MHz) and high-field (400 MHz) NMR spectrometers. The EDBO+ based model was retrained with these four different datasets and the resulting Pareto front predictions provided insight into the effect of data analysis on model predictions. Finally, quaternization of poly(4-vinylpyridine) with bromobutane illustrated the extension of continuous flow chemistry to synthesize functional materials.

Greener and scalable mechanosynthesis of bis(3-indolyl)methane as an example of versatile pharmaceutical scaffold: Is the mechanochemical technique a metal-free process?

The metal-free feature of mechanosynthesis of bis(3-indolyl)methane derivatives using poly(4-vinyl pyridine), a commercially available functional polymer, by ball mill technique at ambient conditions was studied. The condensation of various carbonyl compounds with two indoles smoothly proceeded, and pure products were easily isolated in high to excellent yields. Poly(4-vinylpyridine) exhibited high recyclability without any loss of catalytic activity or change in the chemical structure. The influence of polymer M̅W with a certain PDI on the mechanosynthesis of BIMs was investigated. In addition, the effect of the ball and jar with zirconium oxide material was studied on the rate and yield of the BIMs synthesis process. The method was scalable and generated minimal hazardous wastes. Some merits of the current methodology are such as the good to high yields for various carbonyl compounds and avoiding the use of toxic, expensive, and metal-containing catalysts with a tedious process of preparation, separation, and purification.

Polymer Gel with Tunable Conductive Properties: A Material for Thermal Energy Harvesting.

The spontaneous gelation of poly(4-vinyl pyridine)/pyridine solution produces materials with conductive properties that are suitable for various energy conversion technologies. The gel is a thermoelectric material with a conductivity of 2.2-5.0 × 10-6 S m-1 and dielectric constant ε = 11.3. On the molecular scale, the gel contains various types of hydrogen bonding, which are formed via self-protonation of the pyridine side chains. Our measurements and calculations revealed that the gelation process produces bias-dependent polymer complexes: quasi-symmetric, strongly hydrogen-bonded species, and weakly bound protonated structures. Under an applied DC bias, the gelled complexes differ in their capacitance/conductive characteristics. In this work, we exploited the bias-responsive characteristics of poly(4-vinyl pyridine) gelled complexes to develop a prototype of a thermal energy harvesting device. The measured device efficiency is S = ΔV/ΔT = 0.18 mV/K within the temperature range of 296-360 K. Investigation of the mechanism underlying the conversion of thermal energy into electric charge showed that the heat-controlled proton diffusion (the Soret effect) produces thermogalvanic redox reactions of hydrogen ions on the anode. The charge can be stored in an external capacitor for heat energy harvesting. These results advance our understanding of the molecular mechanisms underlying thermal energy conversion in the poly(4-vinyl pyridine)/pyridine gel. A device prototype, enabling thermal energy harvesting, successfully demonstrates a simple path toward the development of inexpensive, low-energy thermoelectric generators.

Cover Feature: Improvement of Solid Photoluminescence of Tridentate Schiff Base Pt(II) Foldamer by Hybridizing Poly (4‐Vinylpyridine) (Eur. J. Inorg. Chem. 36/2022)

The Cover Feature shows the bis(tridentate Schiff base Pt(II)) complex containing dimethyl sulfoxide (Pt2L2DMSO) as a combination of yellow disks, gray disks, orange cones, and a black curved line. Pt2L2DMSO is unfolding due to the steric repulsion of the bulky ligand. The blue hexagons connected to the branched black lines stand for poly(4-vinylpyridine) (P4VP). The green curved figure in the background indicates hybridization. The top image shows the hybridization of Pt2L2DMSO and P4VP, which causes a ligand exchange reaction for Pt2L2DMSO, forming a folding network structure in the yellow membrane. The yellow membrane exhibits red photoluminescence under ultraviolet irradiation (green wavy arrow). The reddish thunder expresses phosphorescence. The bottom image in the cover shows hybridization of Pt2L2DMSO and 4-vinylpyridine (4VP), which causes a ligand exchange reaction for Pt2L2DMSO, forming the folding columnar packing structure in the brown block crystal. The black wavy arrow indicates non-radiative deactivation. The metallofoldamer crystal does not exhibit solid photoluminescence under ultraviolet irradiation, while the metallofoldamer membrane is luminescent, thanks to the hybridization with P4VP. The background color changes gradually from orange to gray at the bottom to orange at the top, showing the improvement of photoluminescence from bottom to top. More information can be found in the Research Article by H. Achira and co-workers.

Orientation control of the hexagonal and lamellar phases in thin block copolymer films using in-plane AC electric field

Lamellar and hexagonal pattern rearrangements in thin films of polystyrene–block–poly(2-vinyl pyridine) and polystyrene–block–poly(4-vinyl pyridine) copolymers simultaneously exposed to an in-plane AC electric field and saturated chloroform vapor are studied with atomic force microscopy and analyzed via the numerical solution of the self-consistent field theory equations. It is demonstrated that the use of AC field with the root-mean-square strength higher than 8 V⋅μm−1 allows one to effectively orient microphase-separated domains along the field direction on the tens of microns scale. At the same time, the AC field considerably lowers the risk of breakdown and eliminates effects related to ionic transport in the presence of solvent vapor. The role of such factors as the exposure time, field strength and frequency is investigated. Theoretical considerations prove the equivalent effect of AC and DC fields on the structure of the copolymer film in a wide frequency range. Self-consistent field theory calculations of the free energy as a function of film thickness make it possible to exactly identify which phase dominates in the film. In particular, an apparent transformation of standing cylinders into long threads aligned in the field direction should be interpreted as the phase transition from the perpendicular to parallel hexagonal phase, which can take place in a certain range of film thicknesses, provided the electric field strength exceeds a certain threshold value. In the case of a perpendicular lamellar phase, the domain orientation along the direction of the electric field is always profitable. The observed morphological rearrangements under an in-plane field, which preserve connectivity between the film surfaces through the domains of the minor copolymer block, can be important for practical applications.

Polycations inclusion to simultaneously boost permeation and selectivity of two-dimensional TaS2 membranes for acid recovery

Two dimensional (2D) TaS2 laminates have highly regular and ordered transfer mass channels, thus being promising acid recovery membrane candidates for diffusion dialysis (DD) applications to discern H+ and metallic ions. However, it remains a daunting task to get access to high-performance 2D acid recycling membranes made from single TaS2 nanosheets. Here, we report manipulation of the chemical environments of TaS2 channels to develop excellent acid recycling 2D membranes. As demonstration projects, positively charged poly(diallyldimethylammonium chloride) (PDDA) and poly(4-vinylpyridine) (P4VP) in acid solution were chosen as polycation intercalators to modify the TaS2 2D channels. Under the DD mode, the TaS2 membrane exhibits a H+ dialysis coefficient (UH+) of 3.72 × 10−3 m h−1 and separation factor (S) of 9 towards the simulated acid pickle. In contrast, the UH+ and S value of the PDDA@TaS2 membrane improve to 12.7 × 10−3 m h−1 and 34.4 respectively. Those of the P4VP@TaS2 membrane increase to 12.5 × 10−3 m h−1 and 29.1 respectively. The reported acid recovery properties of PDDA@TaS2 and P4VP@TaS2 membranes exceed the commercial DF-120 acid recovery membranes. The experiment and simulation results reveal that the synergistical enhancements of UH+ and S originate from the incorporating polycations in PDDA@TaS2 and P4VP@TaS2 composite channels.

Salt-Induced Transformations of Hybrid Micelles Formed by Anionic Surfactant and Poly(4-vinylpyridine).

Salt-induced structural transformation of charged hybrid surfactant/polymer micelles formed by potassium oleate and poly(4-vinylpyridine) was investigated by cryo-TEM, SANS with contrast variation, DLS, and 2D NOESY. Cryo-TEM data show, that at small salt concentration beads-on-string aggregates on polymer chains are formed. KCl induces the transformation of those aggregates into rods, which is due to the screening of the electrostatic repulsion between similarly charged beads by added salt. In a certain range of salt concentration, the beads-on-string aggregates coexist with the rodlike ones. In the presence of polymer, the sphere-to-rod transition occurs at higher salt concentration than in pure surfactant system indicating that hydrophobic polymer favors the spherical packing of potassium oleate molecules. The size of micelles was estimated by DLS. The rods that are formed in the hybrid system are much shorter than those in polymer-free surfactant solution suggesting the stabilization of the semi-spherical endcaps of the rods by embedded polymer. 2D NOESY data evidence that in the spherical aggregates the polymer penetrates deep into the core, whereas in tighter packed rodlike aggregates it is located mainly at core/corona interface. According to SANS with contrast variation, inside the rodlike aggregates the polymer adopts more compact coil conformation than in the beads-on-string aggregates. Such adaptive self-assembled polymer-surfactant nanoparticles with water-insoluble polymer are very promising for various applications including drag reduction at transportation of fluids.

Silver Nanocrystal Array with Precise Control via Star-like Copolymer Nanoreactors.

Silver nanocrystal arrays had attracted much attention due to the unique plasmonic effect of their ordered nanostructure and the synergy among adjacent nanocrystals. Conventional preparation methods had several limitations, such as high cost, harsh preparation conditions, and complicated influencing factors, which could not be employed to fabricate the nanocrystal arrays in highly controlled fashion. To solve these issues, we reported ordered arrays of different Ag nanocrystals with precise control prepared by utilizing amphiphilic star-like poly(4-vinylpyridine)-block-polystyrene diblock copolymers as nanoreactors synthesized by sequential atom transfer radical polymerization. Moreover, this unimolecular nanoreactor method based on star-like copolymers with stable and predesigned nanostructures was proved to be a universal approach to prepare other nanocrystal arrays. This strategy had low cost, simple process flow, wide applicability, and structural stability that could fabricate nanocrystal array with precise control and continuously prepare more complex nanostructure units in a large scale to meet different functions and applications.