Charged Poly Research Articles

Highly reversible Zn metal anodes enabled by multifunctional poly zinc acrylate protective coating

The application of low-cost and high-safety aqueous Zn metal batteries is seriously hindered by Zn anode stemming from its uncontrollable dendrite growth and detrimental water-induced side reactions. Herein, a zinc-enriched and negatively charged poly zinc acrylate (PZA) polyelectrolyte with hydrophobic 3D network is firstly constructed on Zn surface through facile UV light irradiation of ZA monomer. The as-obtained PZA coating exhibits a strong adhesion to Zn foil, persistently protecting Zn from water corrosion. Furthermore, the 3D interconnected network architecture favors the fast transport of Zn2+. Meanwhile, the anions can be shielded and desolvation of hydrated Zn2+ is accelerated. Notably, the self-contained Zn2+ in PZA can avoid the supply of sluggish ions. Accordingly, the Zn@PZA anode delivers a low energy barrier and high Zn2+ transference number. Moreover, it endows a superior Coulombic efficiency of 99.7 % and long-life dendrite-free plating/stripping (10 mA cm−2, 2 mAh cm−2). The MnO2||Zn@PZA full cell displays a highly stable cycling behavior for over 700 cycles with a high capacity retention of 95.1 % at 1 A/g together with a satisfactory rate performance. This work delivers an affordable and facile strategy to realize the high reversibility and stability of Zn anodes.

Comparison of cationic flocculants with different branching structure for the flocculation of negatively charged particles coexisting with humic substances

Cationic flocculants with varying branching structure sometimes exert dramatically different flocculating abilities on oppositely charged particles. However, their flocculation mechanisms and performances under aqueous conditions in the presence of oppositely charged colloidal particles and polyanions, which commonly exist in natural systems, have not yet been fully elucidated. In this work, three cationic flocculants with different branches per molecule and similar charge densities were used to flocculate negatively charged colloidal particles coexisting with synthetic and naturally occurring polyanions. The electrophoretic mobility of the polymer-coated particles revealed that the branched flocculants required a higher optimum dosage than the linear ones. Under all tested conditions, flocculation was remarkably enhanced by increasing the number of branches in the flocculant. Electrophoretic titrations showed that the interactions between the flocculants and the polyanions to form a polyion complex (PIC) were mainly driven by electrostatic attractions. Hence, the number of branches had no significant effect on PIC formation. These results suggest that unlike the PIC formed by flexible linear flocculants that adopt a flat conformation upon adsorption onto the particle surface, the rigid branched-polyanion PIC tends to retain its shape. This effect is due to the presence of branches that are less prone to undergo relaxation. As a result, a thick adsorbed layer was formed on the particle surface, which improved the effective collision between particles and facilitated bridging flocculation.

Positively Charged Poly(Piperazinamide) Nanofiltration Membranes for the Fast Removal of Metal Ions

AbstractPositively charged nanofiltration (NF) membranes with high perm‐selectivity are highly desired to remove divalent cations such as Ca2+ and Mg2+ ions to ensure the safety of domestic and industrial water supply. In this work, a poly(piperazinamide) NF membrane with a positively charged surface is fabricated via the surfactant‐assembly regulated interfacial polymerization (SARIP) of piperazine (PIP) and 1,3,5‐trimesoyl chloride (TMC). The surfactant assembly can accelerate PIP monomer into the hexane to react with TMC monomer, thus reducing the difference in the trans‐interface diffusion of PIP and the diffusion of TMC in hexane, forming an interfacial polymerization with a stoichiometric characteristic. By tuning the concentration ratio of PIP and TMC, a positively charged poly(piperazinamide) NF membrane will be achieved. At the same time, utilizing the superior hydrophilicity of bacterial cellulose nanofibers nanofilm, a crumpled poly(piperazinamide) active layer is successfully constructed, resulting in a permeating flux up to 22 L m−2 h−1 bar−1 and simultaneously with a MgCl2 rejection >96%. The performance of this positively charged poly(piperazinamide) NF membrane is superior to most other positive NF membranes for the removal of divalent cations so far.

Electrostatic induced peptide hydrogel containing PHMB for sustained antibacterial activity

The bacterial problem seriously endangers public sanitation, especially in wounds, bacteria grow easily and hinder wound healing. In response to the problem of bacterial hazards, we constructed an antibacterial hydrogel by negatively charged peptide Fmoc-FFWDD-OH and positively charged poly (hexamethylene biguanide) hydrochloride (PHMB) through electrostatic interaction. The hydrogel has pH sensitivity and can accurately release the antibacterial agent PHMB under acidic conditions (wound environment), and slow down the release rate and cumulative release amount of PHMB under weak alkaline conditions (physiological environment), so as to reduce the side effects during use. Through the simulation of release model, the release process conformed to the diffusion release mechanism, achieving the sustained release of antibacterial content. In addition, it has been elucidated by various methods that the hydrogel can completely kill bacteria by disrupting the bacterial cell membrane structure and prevent bacterial regrowth. Compared with PHMB, the formation of hydrogel has higher biocompatibility through CKK-8 assays, which may have potential application prospects in the treatment of bacterial-related wounds.

Phase Behaviors of a Binary Blend of Oppositely Charged Polyelectrolytes: A Weak Segregation Approach

In our quest for a better understanding of phase behaviors regarding polyelectrolyte systems, we develop a Landau free energy for a stoichiometric blend of weakly charged polyanions and polycations. Its free energy functional is first formulated as that for Gaussian chains subject to effective interaction fields. The local interaction part, which necessitates excluded volume and charged chain connectivity, is given by a locally equilibrated excess equation of state for the charged hard-sphere chain blend with mean-field dispersion interactions. The long-ranged part of Coulomb interactions is included through an electric potential field generated inside. The resultant functional is then expanded as a series in two proper order parameters to yield the desired Landau free energy. Unfavorable energetics makes the blend phase segregated but only on a nanoscopic scale due to global electroneutrality. The interplay of self- and mutual dispersion interactions produces a variety of phase behaviors ranging from conventional order–disorder-type transitions to complicated ordering transitions in carefully selected blends. Critical compositions are revealed to depend on asymmetry in chain sizes and disparity in self-dispersion interactions between the constituents. Furthermore, it is argued that nanostructured materials with drastically different responses to pressure can be designed by blending polyelectrolytes.

Two-Dimensional Membranes with Highly Charged Nanochannels for Osmotic Energy Conversion.

Inadequate mass transportation of semipermeable membranes causes poor osmotic energy conversion from salinity-gradient. Here, the lamellar graphene oxide membranes (GOMs) constructed with numerous fusiform-like nanochannels, that are pre-filled with negatively charged polyanion electrolytes, to both enhance the ion permeability and ion selectivity of the membrane for energy harvest from the salinty gradient, were developed. The as-prepared membrane achieved the maximum output power density of ∼4.94 W m-2 under a 50 fold salinity gradient, which is 3.5 fold higher than that of pristine GOM. The enhancement could be ascribed to the synergistic impact of the expanded nanochannels and the enhanced space charge density. Via feeding with the artificial salinity water and monovalent cation electrolytes, the system could realise the power output up to 14.7 W m-2 and 34.1 W m-2 , respectively. Overall, this material design strategy could provide an alternative concept to effectively enhance ion transport of other two-dimensional (2D) membranes for specific purposes.

The Dispersion and Coagulation of Negatively Charged Ca2Nb3O10 Perovskite Nanosheets in Sodium Alginate Dispersion.

Chemically exfoliated nanosheets have been extensively employed as functional nanofillers for the fabrication of polymer nanocomposites due to their remarkable electrical, magnetic and optical properties. However, achieving a good dispersion of charged nanosheets in polymer matrix, which will determine the performance of polymer nanocomposites, remains a challenge. Herein, we investigated the dispersion and aggregation behavior of negatively charged Ca2Nb3O10 (CNO) perovskite nanosheets in negatively charged sodium alginate (SA) aqueous dispersion using dynamic light scattering (DLS). When CNO nanosheets meet with SA, aggregation and coagulation inevitably occurred owing to the absorption of SA on nanosheets. By controlling the electrostatic attraction between positively charged poly(ethylene imine) (PEI) and negatively charged SA, the charge density and hydrodynamic size of SA can be tuned to enable the good dispersion of CNO nanosheets in SA. This result may provide a new strategy to achieve the good dispersion of charged nanosheets in charged polymers for the rational design of multifunctional nanocomposites.

Influences of Permeate Solution and Feed pH on Enhancement of Ammonia Recovery from Wastewater by Negatively Charged PTFE Membranes in Direct Contact Membrane Distillation Operation.

This research investigated the feasibility of enhancing ammonia recovery from wastewater using a negatively charged poly(tetrafluoroethylene) (PTFE) membrane in a direct contact membrane distillation (DCMD) system. The influences of phosphate solution types (as the permeate solutions) and feed pH on ammonia recovery were analyzed. Three types of permeate solutions—DI water and two types of phosphate solutions (H3PO4 and KH2PO4)—were investigated for recovery of ammonia gas on the permeate side. From the obtained results, the H3PO4 solution was found to be the most suitable permeate solution to recover ammonia gas in the DCMD operation with the highest overall ammonia mass transfer coefficient of 7.4 × 10–5 m/s, compared to values of 1.2 × 10–5 and 2.4 × 10–5 m/s for DI water and KH2PO4 solution, respectively. Moreover, an increase in the H3PO4 concentration from 0.3 to 0.5 M in the permeate solution also could significantly enhance ammonia recovery. With an increase in the feed pH from 10.0 to 11.8, the ammonia recovery could be enhanced to 92.98% at a pH of 11.8. Liquid ammonium phosphate fertilizer could be produced by the DCMD system with the use of 0.5 M H3PO4 solution. Therefore, the DCMD process using a negatively charged PTFE membrane with an appropriate permeate solution is one of the challenging processes for ammonia recovery from wastewater to promote the circular economy concept.

Complexation in Aqueous Solution of a Hydrophobic Polyanion (PSSNa) Bearing Different Charge Densities with a Hydrophilic Polycation (PDADMAC).

In this work the electrostatic complexation of two strong polyelectrolytes (PEs) was studied, the hydrophilic and positively charged poly (diallyldimethylammonium chloride) (PDADMAC) and the hydrophobic and negatively charged poly (styrene-co-sodium styrene sulfonate) (P(St-co-SSNa)), which was prepared at different sulfonation rates. The latter is known to adopt a pearl necklace conformation in solution for intermediate sulfonation rates, suggesting that a fraction of the P(St-co-SSNa) charges might be trapped in these hydrophobic domains; thus making them unavailable for complexation. The set of complementary techniques (DLS, zetametry, ITC, binding experiment with a cationic and metachromatic dye) used in this work highlighted that this was not the case and that all anionic charges of P(St-co-SSNa) were in fact available for complexation either with the polycationic PDADMAC or the monocationic o-toluidine blue dye. Only minor differences were observed between these techniques, consistently showing a complexation stoichiometry close to 1:1 at the charge equivalence for the different P(St-co-SSNa) compositions. A key result emphasizing that (i) the strength of the electrostatic interaction overcomes the hydrophobic effect responsible for pearl formation, and (ii) the efficiency of complexation does not depend significantly on differences in charge density between PDADMAC and P(St-co-SSNa), highlighting that PE chains can undergo conformational rearrangements favoring the juxtaposition of segments of opposite charge. Finally, these data have shown that the formation of colloidal PECs, such as PDADMAC and P(St-co-SSNa), occurs in two distinct steps with the formation of small primary complex particles (<50 nm) by pairing of opposite charges (exothermic step) followed by their aggregation within finite-size clusters (endothermic step). This observation is in agreement with the previously described mechanism of PEC particle formation from strongly interacting systems containing a hydrophobic PE.

Coacervation between Two Positively Charged Poly(ionic liquid)s.

Complex coacervates are usually formed through electrostatic attraction between oppositely charged polyelectrolytes, with a few exceptions such as coacervates of like-charge proteins and polyelectrolytes, both in vivo and in vitro. Understanding of the preparation and mechanisms of these coacervates is limited. Here, a positively charged poly(ionic liquid), poly(1-vinyl-3-benzylimidazolium chloride) (PILben), is designed that bears benzene rings in repeating units. Fluidic coacervates are prepared by mixing the PILben aqueous solution with a like-charge poly(ionic liquid) named poly(dimethyl diallyl ammonium chloride) (PDDA). The effects of polymer concentration, temperature, and ionic strength in the PILben-PDDA coacervate are studied. Raman spectroscopy and 2D 1 H-13 C heteronuclear single quantum coherence (1 H-13 C HSQC) characterizations verify that the coacervate formation benefits from the cation-π interaction between PILben and PDDA. This work provides principles and understandings of designing coacervates derived from like-charge poly(ionic liquids) with high charge density.

Two Sides of the Same Coin: A Unified Theoretical Treatment of Polyelectrolyte Complexation in Solution and Layer-by-Layer Films

Polyelectrolyte coacervates, obtained by mixing solutions of oppositely charged polyions, and layer-by-layer films, produced by sequential adsorption of polyelectrolytes on a surface, are two types of closely related soft materials. While both types of materials are produced by polyelectrolyte complexation, their theoretical description had so far followed divergent paths. This work reports a unifying theoretical treatment of polyelectrolyte complexation in solution and layer-by-layer self-assembled thin films using a molecular theory that describes polyelectrolyte complexation by using a chemical-equilibrium formalism. The theory is shown to predict both the phase diagrams of polyelectrolyte mixtures in solution and the formation of layer-by-layer thin films in good agreement with experimental evidence. In the latter case, the theory correctly captures the effects of solution pH and ionic strength on the mass of the deposited films as well as the possibility of layer-by-layer deposition without full charge reversal at extreme pHs. The theory is then used to revisit the “universal curve” for the effect of salt concentration on layer-by-layer deposition previously proposed on experimental grounds by Salehi et al. [Macromolecules 2015, 48, 400–409]. This universal curve makes predictions about the growth rate of a layer-by-layer film for a given polyanion/polycation pair by using only information obtained from a mixture of the same polyelectrolytes in solution, thereby linking both phenomena. Our theoretical results confirm the validity of the curve. This achievement demonstrates the practical importance of describing polyelectrolyte coacervates and multilayer films within a unified theoretical framework.

An electrostatic self-assembly approach to prepare tebuconazole nanoparticles with improved sustained release and enhanced antifungal activity

Compared with the traditional pesticides, the nanopesticides (NPs) exhibit better sustained release performance, higher utilization efficiency and reduction of environmental pollution. In this study, the antifungal tebuconazole (TEB) loaded nanoparticles (TEB NPs) were prepared by electrostatic self-assembly of the positively charged poly dimethyl diallyl ammonium chloride (PDADMAC) and sulfobutylether-β-cyclodextrin (SCD) inclusion complex (TEB-SCD) with negative charge. The water solubility and thermal stability of TEB were significantly improved after forming the inclusion complex. The blank NPs and TEB NPs were both characterized by particle size, zeta potential, scanning electron microscopy (SEM), sustained release and antifungal activity. The average particle size of the TEB NPs were 411.75 ± 61.65 nm, and the polydispersity index (PDI) showed low values (< 0.3). The TEB NPs were stable for at least 28 days at 25 °C. Compared with pure TEB, TEB NPs showed the sustained release properties. In addition, TEB NPs exhibited better antifungal activity than TEB industrial concentrate (TC, 98%) and commercially available TEB suspension concentrate (SC) with the 96.33 ± 13.52% antifungal rate of fusarium graminearum. The results indicated that the TEB NPs can improve the antifungal activity and reduce environmental pollution.

Unleashing Insulating Polymer as Charge Transport Cascade Mediator

AbstractCrafting spatially controllable charge transfer channels at the nanoscale level remains an enduring challenge in solar‐to‐chemical conversion technology. Despite the advancements, it still suffers from sluggish interfacial charge transport kinetics and scarcity of strategies to finely modulate charge transport pathways. Herein, this article demonstrates the unexpected charge modulation property of non‐conjugated insulating polymer assisted by a universal layer‐by‐layer self‐assembly tactic. Oppositely charged poly(dimethyl diallyl ammonium chloride) (PDDA) and Ti3C2 MXene quantum dots (MQDs) are periodically attached to the wide bandgap metal oxides (WMOs) to design multilayered heterostructured photoanodes. The intermediate PDDA layer acts as an efficacious charge relay medium to access directional electron flow from WMOs to Ti3C2 MQDs, while Ti3C2 MQDs serve as the electron extractor. Charge transfer cascade is thus stimulated on account of the simultaneous electron‐trapping capabilities of interim PDDA layer and Ti3C2 MQDs, which synergistically favors the conspicuously boosted charge separation over WMOs, affording the WMOs/(PDDA/MQDs)n photoanodes with considerably enhanced photoelectrochemical (PEC) water oxidation performances. Moreover, PEC performances of such photoanodes can be tuned by interface configuration via assembly number and sequence. This work will provide an insightful perspective to craft a directional charge transfer pathway through insulating polymer for solar energy conversion.

Drug-free neutrally charged polypeptide nanoparticles as anticancer agents.

Cationic synthetic anticancer polymers and peptides have attracted increasing attention for advancing cancer treatment without causing drug resistance development. To circumvent in vivo instability and toxicity caused by cationic charges of the anticancer polymers/peptides, we report, for the first time, a nanoparticulate delivery system self-assembled from a negatively charged pH-sensitive polypeptide poly(ethylene glycol)-b-poly(ʟ-lysine)-graft-cyclohexene-1,2-dicarboxylic anhydride and a cationic anticancer polypeptide guanidinium-functionalized poly(ʟ-lysine) (PLL-Gua) via electrostatic interaction. The formation of nanoparticles (Gua-NPs) neutralized the positive charges of PLL-Gua. Both PLL-Gua and Gua-NPs killed cancer cells in a dose- and time-dependent manner, and induced cell death via apoptosis. Confocal microscopic studies demonstrated that PLL-Gua and Gua-NPs readily entered cancer cells, and Gua-NPs were taken up by the cells via endocytosis. Notably, Gua-NPs and PLL-Gua exhibited similar in vitro anticancer efficacy against MCF-7 and resistant MCF-7/ADR. PLL-Gua and Gua-NPs also induced similar morphological changes in MCF-7/ADR cells compared to MCF-7 cells, further indicating their ability to bypass drug resistance mechanisms in the MCF-7/ADR cells. More importantly, Gua-NPs with higher LD50 and enhanced tumor accumulation significantly inhibited tumor growth with negligible side effects in vivo. Our findings shed light on the in vivo delivery of anticancer peptides and opened a new avenue for cancer treatment.

Highly efficient and reversible iodine capture utilizing amorphous conjugated covalent triazine-based porous polymers: Experimental and computational studies

A robust conjugated covalent triazine framework, CTF-DPA, has been synthesized through a facile Friedel-Crafts alkylation reaction using cyanuric chloride as the cross-linking agent and diphenylacetylene (DPA) as the backbone building block. Benefiting from its unique textural and structural features such as high specific surface area (943 m2 g−1), accessible pores, and abundant π-electrons, CTF-DPA exhibits outstanding iodine-capturing performance. It features an ultrahigh iodine vapor capture capacity of 5.12 g g−1 at 75 °C and 1 bar and a remarkable iodine adsorption capacity of 667 mg g−1 in n-hexane solution. To the best of our knowledge, these are among the highest iodine adsorption capacities reported for porous organic polymers. In contrast, an analog CTF synthesized with trans-stilbene (TS) replacing DPA instead features a slight decrease in specific surface area (919 m2 g−1) but a noticeable reduction in iodine adsorption capacities. The iodine uptake mechanism was investigated by Fourier-transform infrared (FT-IR), X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray spectroscopy (EDX), and Raman spectroscopy as well as computationally. Density-functional theory (DFT) calculations reveal that charge transfer from conjugated C≡C, phenyl, and triazine moieties to iodine molecules facilitates the generation of charged (poly)iodide species (e.g.,I3−), enhancing the adsorption affinity/capacity. Moreover, CTF-DPA could be recycled five times while preserving above 87.6% of its initial iodine uptake capacity.

Label-Free Detection of Saxitoxin with Field-Effect Device-Based Biosensor.

Saxitoxin (STX) is a highly toxic and widely distributed paralytic shellfish toxin (PSP), posing a serious hazard to the environment and human health. Thus, it is highly required to develop new STX detection approaches that are convenient, desirable, and affordable. This study presented a label-free electrolyte-insulator-semiconductor (EIS) sensor covered with a layer-by-layer developed positively charged Poly (amidoamine) (PAMAM) dendrimer. An aptamer (Apt), which is sensitive to STX was electrostatically immobilized onto the PAMAM dendrimer layer. This results in an Apt that is preferably flat inside a Debye length, resulting in less charge-screening effect and a higher sensor signal. Capacitance-voltage and constant-capacitance measurements were utilized to monitor each step of a sensor surface variation, namely, the immobilization of PAMAM dendrimers, Apt, and STX. Additionally, the surface morphology of PAMAM dendrimer layers was studied by using atomic force microscopy and scanning electron microscopy. Fluorescence microscopy was utilized to confirm that Apt was successfully immobilized on a PAMAM dendrimer-modified EIS sensor. The results presented an aptasensor with a detection range of 0.5–100 nM for STX detection and a limit of detection was 0.09 nM. Additionally, the aptasensor demonstrated high selectivity and 9-day stability. The extraction of mussel tissue indicated that an aptasensor may be applied to the detection of STX in real samples. An aptasensor enables marine toxin detection in a rapid and label-free manner.

Quantum Dot-Embedded Hybrid Photocatalytic Nanoreactors for Visible Light Photocatalysis and Dye Degradation

Utilization of visible light to drive chemical transformations is a fascinating field of research and particularly important in the current socioeconomic context. However, bare photocatalysts often undergo photodegradation or agglomeration, which limits their recyclability. In this regard, designing robust and flexible artificial photocatalytic nanoreactors with embedded catalytic units finds tremendous importance in recent times. Herein, we utilized quantum dot (QD)-embedded coacervate nanodroplets (NDs) as photocatalytic nanoreactors for model chemical transformations, which are otherwise inefficient with bare QDs in bulk aqueous solution. Hybrid NDs fabricated from negatively charged CdTe QDs and positively charged poly(diallyldimethyl) ammonium chloride (PDADMAC) have been exploited as a confined host toward efficient visible light-driven photoredox transformation of ferricyanide (Fe3+) to ferrocyanide (Fe2+) and photocatalytic dye degradation of rhodamine B and methylene blue. The present NDs display excellent recyclability without any appreciable decrease in the conversion yield and reaction kinetics. Our findings suggest the involvement of individual QDs embedded within these NDs as the active photocatalytic site for these transformations. The observed photocatalytic activity of the QD-embedded NDs arises due to the combined effect of surface charge modulation of embedded QDs and nanoconfinement inside the nanoreactor. The present study paves the way for designing next-generation photocatalytic nanoreactors toward a vast array of photochemical conversions involving semiconductor nanoparticles.

Surface grafting with diverse charged chemical groups mitigates calcium phosphate scaling on reverse osmosis membranes during municipal wastewater desalination

Calcium phosphate scaling on reverse osmosis (RO) membranes during the desalination of municipal wastewater remains a major problem. This study modified RO membranes by graft polymerization using hydrophilic methacrylate monomers to reduce scaling and investigated the effects of surface charge and exposed functional groups on scaling during municipal wastewater desalination. Grafting was performed using negatively charged, neutral, positively charged, and mixed charge monomers. Testing the modified membranes during RO desalination of a solution simulating treated domestic wastewater effluents from the Shafdan wastewater reclamation plant in Israel revealed improved antiscaling performance by grafted membranes compared with the pristine (unmodified) membrane. In particular, membranes grafted using neutral and mixed charge monomers showed the best antiscaling tendencies: 25.6% and 27.6% decrease in flux, respectively, compared with a 59.1% decrease using the pristine membrane. These results, together with physico-chemical characterization, suggested that calcium phosphate precipitation and scaling on the grafted RO membranes are driven mainly by electrostatic and dipole–dipole interactions between charged chemical groups exposed on the membrane surface and ionic species in the test solution; these interactions are minimized in membranes grafted with neutral or mixed charge poly (methacrylate) groups, resulting in enhanced antiscaling performance. This study provides insight into the antiscaling mechanisms of hydrophilic poly (methacrylate) chains grafted on RO membranes, and thus can potentially aid efforts to mitigate calcium phosphate scaling during RO desalination of municipal wastewater. • Diverse charged monomers grafted on RO membrane to mitigate Ca 3 (PO 4 ) 2 scaling. •Grafted membranes exhibit enhanced performance in RO wastewater desalination. •Neutral and mixed-charge grafted polymers show lowest flux decline. •Electrostatic interactions of surface functional groups with ions dominate scaling.

Electrostatically cooperative host-in-host of metal cluster \u2282 ionic organic cages in nanopores for enhanced catalysis

The construction of hierarchically nanoporous composite for high-performance catalytic application is still challenging. In this work, a series of host-in-host ionic porous materials are crafted by encapsulating ionic organic cages into a hyper-crosslinked, oppositely charged porous poly(ionic liquid) (PoPIL) through an ion pair-directed assembly strategy. Specifically, the cationic cage (C-Cage) as the inner host can spatially accommodate a functional Au cluster, forming a [Au⊂C-Cage+]⊂PoPIL− supramolecular composite. This dual-host molecular hierarchy enables a charge-selective substrate sorting effect to the Au clusters, which amplifies their catalytic activity by at least one order of magnitude as compared to Au confined only by C-Cage as the mono-host (Au⊂C-Cage+). Moreover, we demonstrate that such dual-host porous system can advantageously immobilize electrostatically repulsive Au⊂C-Cage+ and cationic ferrocene co-catalyst (Fer+) together into the same microcompartments, and synergistically speed up the enzyme-like tandem reactions by channelling the substrate to the catalytic centers via nanoconfinement.

Negatively charged poly(N-isopropyl acrylamide-co-methacrylic acid)/polyacrylamide semi-IPN hydrogels: Correlation between swelling and compressive elasticity

A series of thermoresponsive semi-interpenetrating polymer network (semi-IPN) based on linear polyacrylamide (PAAm), N-isopropylacrylamide (NIPA) and methacrylic acid (MA) were synthesized by varying linear polymer content via free radical polymerization. An interpenetrated network of P(NIPA-MA)/PAAm was designed to modulate elasticity by varying inner composition and to improve rate of swelling-deswelling phenomenon. Correlation between swelling and compression elasticity was demonstrated. Inclusion of linear PAAm chains with high molecular weight (Mw = 9.639 × 105 g/mol) into P(NIPA-MA) network induced physical entanglements, increased apparent crosslinking density νeand enlarged compressive elasticity. Dependence of νeon linear polymer content was expressed as a cubic polynomial function. Extent of swelling of semi-IPN P(NIPA-MA)/PAAm gels was sensitive to presence of linear PAAm chains. Existence of linear polymer decreased apparent ionic group density and increased crosslinking density compared to that of copolymer P(NIPA-MA) network which in turn decreased equilibrium swelling. A significant increase in swelling/shrinking rate was observed in the presence of linear PAAm. Due to ionization of carboxylic acid groups in P(NIPA-MA) network, semi-IPN P(NIPA-MA)/PAAm gels showed different degrees of swelling depending on linear PAAm content and temperature of swelling medium. Semi-IPNs exhibited phase transition temperatures shifted higher temperature, suggesting physical entanglements between P(NIPA-MA) network and linear PAAm. Increasing swelling temperature resulted in an increase in Flory-Huggins interaction parameter. Entropic contributionχSincreased and enthalpic contribution χH decreased with PAAm content. The results showed that the prepared semi-IPNs are a suitable adsorbent for adsorption of the cationic dye Methyl violet (MV). Adsorption kinetics followed a pseudo-second-order model and exhibited a two-stage intra-particle diffusion. A detailed understanding of physicochemical properties of negatively charged thermoresponsive semi-IPNs in relation to structural architecture is an important criterion in many biomedical and pharmaceutical applications.