Abstract: Silver nanoparticles have antibacterial properties, but their use has been a cause for concern because they persist in the environment. Here, we show that lignin nanoparticles infused with silver ions and coated with a cationic polyelectrolyte layer form a biodegradable and green alternative to silver nanoparticles. The polyelectrolyte layer promotes the adhesion of the particles to bacterial cell membranes and, together with silver ions, can kill a broad spectrum of bacteria, including Escherichia coli, Pseudomonas aeruginosa and quaternary-amine-resistant Ralstonia sp. Ion depletion studies have shown that the bioactivity of these nanoparticles is time-limited because of the desorption of silver ions. High-throughput bioactivity screening did not reveal increased toxicity of the particles when compared to an equivalent mass of metallic silver nanoparticles or silver nitrate solution. Our results demonstrate that the application of green chemistry principles may allow the synthesis of nanoparticles with biodegradable cores that have higher antimicrobial activity and smaller environmental impact than metallic silver nanoparticles.

Abstract: The present work introduces an origin of sensing function of polyelectrolyte-coated colloids based onTb(III) complexes with calix[4]resorcinarene cavitand bearing four 1,3-diketone groups at the upperrim. The Tb(III)-centered luminescence of the colloids remains unchanged at pH 3–9, although theTb(III) complexes are highly pH-dependent in DMF solutions. Both colloidal and luminescent proper-ties of the colloids are stable within one month at least, which reveals stability of complex-based hardnanotemplates and soft polyelectrolyte deposition. The chelating substrates (catechol, tetracycline andfluoroquinolone derivatives)inducequickandreproducibleluminescentresponseofthecomplex-basedcolloids without any detectable changes of their colloidal properties. The ternary complex formation atthe interface of the colloids is the reason for their luminescent response on the substrates in aqueoussolutions. BoththeinsolubilityoftheTb(III)-containingcoresandtheshieldingand/orbuffereffectofthepolyelectrolyte coating affect the interfacial complex formation, which results in more selective lumi-nescent response of the colloids on the tetracycline and fluoroquinolone antibiotics in comparison withthe complexes in solutions.© 2015 Elsevier B.V. All rights reserved.

Abstract: Complexes that form between oppositely charged polyelectrolytes may be solid or liquid. Here, Perry et al. show that chirality in polypeptides can determine the state of those complexes based on a propensity for hydrogen-bond formation.

Abstract: We report a small angle neutron scattering (SANS) and rheology study of cellulose derivative polyelectrolyte sodium carboxymethyl cellulose with a degree of substitution of 1.2. Using SANS, we establish that this polymer is molecularly dissolved in water with a locally stiff conformation with a stretching parameter[Formula: see text]. We determine the cross sectional radius of the chain ([Formula: see text] 3.4 A) and the scaling of the correlation length with concentration (ξ = 296 c (-1/2)A for c in g/L) is found to remain unchanged from the semidilute to concentrated crossover as identified by rheology. Viscosity measurements are found to be in qualitative agreement with scaling theory predictions for flexible polyelectrolytes exhibiting semidilute unentangled and entangled regimes, followed by what appears to be a crossover to neutral polymer concentration dependence of viscosity at high concentrations. Yet those higher concentrations, in the concentrated regime defined by rheology, still exhibit a peak in the scattering function that indicates a correlation length that continues to scale as[Formula: see text]. © 2014 The Authors. Journal of Polymer Science Part B: Polymer Physics Published by Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015, 53, 492-501.

Abstract: We studied the impact of anionic polysaccharide (κ-carrageenan) as a co-gelator of gelatin at different physico-chemical and by varying the κ-carrageenan/gelatin ratio. It has been shown that increasing κ-carrageenan concentration accelerates the gelation and leads to significant increase in the viscoelastic parameters of the modified gels. Non-linearity of viscoelastic properties becomes evident in much lower deformations in comparison with those of native gelatin gels. The strength of gels characterized by the yield stress also increases along with κ-carrageenan concentration. The deformation (but not flow) of gels happens along the rupture surfaces appearing at the apparent yield stress. The melting temperature increases until 45 °C for high κ-carrageenan/gelatin ratio. The suggested explanation of the observed changes in properties of modified gels relates these effects with formation of complexes of gelatin and polysaccharide. FT-IR spectroscopy data show that (bio)polyelectrolyte complex formation is due to electrostatic interaction between positively charged groups in gelatin and negatively charged sulfate groups in κ-carrageenan that leads to conformation changes of gelatin macromolecules. Micrographs (scanning electron microscopy) show that addition of even a small quantity of polysaccharide leads to radical changes in supramolecular structure of modified gels.

Abstract: Anion exchange membranes (AEMs) have been recognized as one of the most prospective polyelectrolytes for fuel cells due to their faster electrode reaction kinetics and the potential of adopting cheaper metal catalysts against proton exchange membranes (PEMs). Herein, a series of poly(arylene ether sulfone)s containing a flexible pendant imidazolium cation were synthesized by grafting bromine-bearing imidazolium-based ionic liquids into a hydroxyl-bearing poly(ether sulfone) matrix. 1H NMR spectroscopy was used to confirm the as-synthesized copolymers. Atomic force microscopy (AFM) and small angle X-ray scattering (SAXS) were used to characterize the morphology of the membranes. The incorporation of the flexible side-chain imidazolium groups is beneficial to the aggregation of the ionic clusters leading to the formation of hydrophilic/hydrophobic phase-separated morphology and nano-channels. As a result, an enhancement in the ionic conductivity can be achieved. Therefore, the as-prepared AEMs possess higher ionic conductivity than traditional benzyl-type AEMs. The weight-based ion exchange capacity (IECw) of the membranes was in the range of 1.01–1.90 meq. g−1. Correspondingly, their ionic conductivity was in the range of 22.13–59.19 and 51.66–108.53 mS cm−1 at 30 and 80 °C, respectively. Moreover, the membranes also exhibit good alkaline stability and interesting single cell performance. This work presents a facile and universal route for the synthesis of AEMs with superior performance.

Abstract: Nanoporous ionic organic networks (PIONs) with a high ionic density 9 (three cation−anion pairs per unit) have been synthesized by a facile S N 2 nucleophilic 10 substitution reaction. Owing to the electrostatic and steric effect, those ionic networks 11 with porous channels can stabilize and support gold (Au) nanoparticles (NPs) in 1−2 12 nm. The Au@PION hybrid materials used as an heterogeneous catalyst were highly 13 active, selective, and stable in the aerobic oxidation of saturated alcohols. 14 KEYWORDS: Gold nanoparticles, gold catalysis, porous polyelectrolyte, porous poly(ionic liquid)s, aerobic oxidation 15 D uring the past decade, the possibility of modulating the 16 physicochemical properties of ionic liquids (ILs) by an 17 appropriate combination of cations and anions allied to their 18 supramolecular organization enables the ILs-mediated prepara- 19 tion of metallic nanoparticles (NPs). 1−5 Meanwhile, gold (Au) 20 NPs with increased fractions of edges and corners have been

Abstract: We report on a molecular fabrication approach to precisely control surface ζ potentials of polymeric thin layers constructed by electrostatic layer-by-layer (LbL) assembly methods. The protocol established allows us to achieve surface isoelectric points (IEP) in the pH range of 6–10. Poly(acrylic acid) (PAA, a weak polyanion) and poly(diallyldimethylammonium chloride) (PDADMAC, a strong polycation) were chosen to build up the bulk films. The weak polycation polyethylenimine (PEI) was applied as a top layer. A unique feature of this approach is that the chemical composition of the top layer is not affected by the manipulation of the ζ potential of the films. Surface charge tuning is achieved by controlling the degree of ionization of the weak polyelectrolytes at various pH values and subsequent manipulation of the amount of polyelectrolyte deposited in the penultimate and last layers, respectively. Following assembly and characterization, the films were used as candidates for antifouling surfaces. The foul...

Abstract: In this work, nanocontainers based on layered double hydroxide (LDH) loaded with two different corrosion inhibitors, namely 2-mercaptobenzothiazole (MBT) and cerium(III) nitrate, were prepared. MBT was intercalated into LDH galleries in anionic form by anion-exchange, while Ce3+ was fixed between polyelectrolyte layers on the surface of LDH-MBT nanoplatelets by the Layer-by-Layer (LbL) method. Both inhibitors were found in the modified LDHs (LDH-Mod) by X-ray diffraction and scanning electron microscopy coupled with energy dispersive spectroscopy. The release studies performed by UV-vis spectrophotometry indicated that the main triggering conditions for release of MBT from LDHs changed when LDH nanoplatelets were covered with polyelectrolytes. Furthermore, electrochemical impedance spectroscopy and DC polarization were used to investigate the effect in combining MBT− and Ce3+ within the same nanocontainer, for the corrosion protection of 2024-T3 aluminium alloy directly in solution as well as in a hybrid sol–gel coating. The obtained results open prospects for application of these systems as additives in multifunctional smart coatings.

Abstract: Polyelectrolyte complexes (PECs) form by mixing polycation and polyanion solutions together, and have been explored for a variety of applications. One challenge for PEC processing and application is that under certain conditions the as-formed PECs aggregate and precipitate out of suspension over the course of minutes to days. This aggregation is governed by several factors such as electrostatic repulsion, van der Waals attractions, and hydrophobic interactions. In this work, we explore the boundary between colloidally stable and unstable complexes as it is influenced by polycation/polyanion mixing ratio and ionic strength. The polymers examined are poly(diallyldimethylammonium chloride) (PDAC) and poly(sodium 4-styrenesulfonate) (PSS). Physical properties such as turbidity, hydrodynamic size, and zeta potential are investigated upon complex formation. We also perform detailed molecular dynamics simulations to examine the structure and effective charge distribution of the PECs at varying mixing ratios and salt concentrations to support the experimental findings. The results suggest that the colloidally stable/unstable boundary possibly marks the screening effects from added salt, resulting in weakly charged complexes that aggregate. At higher salt concentrations, the complexes initially form and then gradually dissolve into solution.

Abstract: This work presents molecular-level investigations of how well-characterized silica-supported phospholipid bilayers formed from either pure DOPC or a 9:1 mixture of DOPC:DOTAP interact with positively and negatively charged 4 nm gold metal nanoparticles at pH 7.4 and NaCl concentrations ranging from 0.001 to 0.1 M. Second harmonic generation (SHG) charge screening measurements indicate the supported bilayers carry a negative interfacial potential. Resonantly enhanced SHG measurements probing electronic transitions within the gold core of the nanoparticles show the particles interact irreversibly with the supported bilayers at a range of concentrations. At 0.1 M NaCl, surface coverages for the particles functionalized with the negatively charged ligand mercaptopropionic acid (MPA) or wrapped in the cationic polyelectrolyte poly(allylamine) hydrochloride (PAH) are estimated from a joint analysis of QCM-D, XPS, AFM, and ToF-SIMS to be roughly 1 × 107 and 1 × 1011 particles cm–2, respectively. Results from com...

Abstract: A study was made of the anti-polyelectrolyte effect of a model polyzwitterion at the single-chain level and from the point of view of comparison with inorganic salts and organic inner salts. A well-defined polymer of sulfobetaine was synthesized and fluorescently labeled. Fluorescence correlation spectroscopy was adopted to probe diffusion and chain size of polyzwitterion single chains in extremely dilute aqueous solutions over a broad concentration range of added salts. By the introduction of inorganic salts and organic inner salts, the single chains of polyzwitterions expanded with an increase of salt concentration. This observation indicates that the break-up of the dipole-dipole attraction between the zwitterion units is the mechanism of the anti-polyelectrolyte effect of polyzwitterions. The difference in the strength of the anti-polyelectrolyte effect induced by inorganic salts and organic inner salts also indicates the partial contribution from the asymmetric adsorption of ions onto polyzwitterion chains. (c) 2015 Society of Chemical Industry

Abstract: Polyelectrolyte complexes formed between chitosan (CS) and anionic polymers have attracted increasing interest in drug delivery. In this study, CS is copolymerized with hypromellose via a coupling reagent-mediated approach to form a water-soluble, nontoxic CS derivative, namely hypromellose-graft-CS (HC), which is subsequently complexed with carboxymethylcellulose (CMC) to generate a polyampholytic hydrogel. When compared with conventional CS, HC is highly water-soluble across a wide pH range, and has a substantially higher pH buffering capacity to provide a pH-stable environment for delivery of drugs. In addition, the polyelectrolyte complex of HC exhibits a drug encapsulation efficiency of over 90% in all drugs tested, which is 1–2 fold higher than the efficiency attainable by the polyelectrolyte complex of conventional CS, with a 2–3 fold longer duration of sustained drug release. Our results indicate that as a novel polymer, HC has excellent promise for future pharmaceutical applications.

Abstract: Ion transport of multi-ionic solutions through layered electrolyte and polyelectrolyte structures are relevant in a large variety of technical systems such as micro and nanofluidic devices, sensors, batteries and large desalination process systems. We report a new direct numerical simulation model coined EnPEn: it allows to solve a set of first principle equations to predict for multiple ions their concentration and electrical potential profiles in electro-chemically complex architectures of n layered electrolytes E and n polyelectrolytes PE. EnPEn can robustly capture ion transport in sub-millimeter architectures with submicron polyelectrolyte layers. We proof the strength of EnPEn for three yet unsolved architectures: (a) selective Na over Ca transport in surface modified ion selective membranes, (b) ion transport and water splitting in bipolar membranes and (c) transport of weak electrolytes.

Abstract: Layer-by-layer (LbL) self-assemblies have inherent potential as dynamic coatings because of the sensitivity of their building blocks to external stimuli. Here, humidity serves as a feasible trigger to activate the self-healing of a microporous polyethylenimine/poly(acrylic acid) multilayer film. Microporous structures within the polyelectrolyte multilayer (PEM) film are created by acid treatment, followed by freeze-drying to remove water. The self-healing of these micropores can be triggered at 100% relative humidity, under which condition the mobility of the polyelectrolytes is activated. Based on this, a facile and versatile method is suggested for directly integrating hydrophobic drugs into PEM films for surface-mediated drug delivery. The high porosity of microporous film enables the highest loading (≈303.5 μg cm−2 for a 15-bilayered film) of triclosan to be a one-shot process via wicking action and subsequent solvent removal, thus dramatically streamlining the processes and reducing complexities compared to the existing LbL strategies. The self-healing of a drug-loaded microporous PEM film significantly reduces the diffusion coefficient of triclosan, which is favorable for the long-term sustained release of the drug. The dynamic properties of this polymeric coating provide great potential for its use as a delivery platform for hydrophobic drugs in a wide variety of biomedical applications.

Abstract: To mimic the underwater adhesion of marine mussels, a bioadhesive has been prepared with a poly(acrylic acid) backbone functionalized with 30% catechol appendants. The polyelectrolyte chains can be reversibly crosslinked through metal chelation and irreversibly gelled by oxidative crosslinking. Surprisingly, the reported “poor” metal chelator Zn2+ not only imparts this injectable adhesive with superior adhesion after the formation of coacervation compared to the one chelated by a stronger metal crosslinker (e.g. Fe3+), but also generates good mechanical performance of the self-healing hydrogel after the oxidation of catechol groups with a pH trigger. Such a pH-responsive material with strong adhesion and good self-healing property at different conditions could be an ideal candidate in biomedical adhesion and tissue engineering.

Abstract: We present simulations of aqueous polyelectrolyte complexes with new MARTINI models for the charged polymers poly(styrene sulfonate) and poly(diallyldimethylammonium). Our coarse-grained polyelectrolyte models allow us to study large length and long time scales with regard to chemical details and thermodynamic properties. The results are compared to the outcomes of previous atomistic molecular dynamics simulations and verify that electrostatic properties are reproduced by our MARTINI coarse-grained approach with reasonable accuracy. Structural similarity between the atomistic and the coarse-grained results is indicated by a comparison between the pair radial distribution functions and the cumulative number of surrounding particles. Our coarse-grained models are able to quantitatively reproduce previous findings like the correct charge compensation mechanism and a reduced dielectric constant of water. These results can be interpreted as the underlying reason for the stability of polyelectrolyte multilayers and complexes and validate the robustness of the proposed models.

Abstract: Thin films of complexes made from oppositely charged polyelectrolytes have applications as supported membranes for separations, cell growth substrates, anticorrosion coatings, biocompatible coatings, and drug release media, among others. The relatively recent technique of layer-by-layer assembly reliably yields conformal coatings on substrates but is impractically slow for films with thickness greater than about 1 μm, even when accelerated many fold by spraying and/or spin assembly. In the present work, thin, uniform, smooth films of a polyelectrolyte complex (PEC) are rapidly made by spin-coating a polyelectrolyte coacervate, a strongly hydrated viscoelastic liquidlike form of PEC, on a substrate. While the apparatus used to deposit the PEC film is conventional, the behavior of the coacervate, especially the response to salt concentration, is highly nontraditional. After glassification by immersion in water, spun-on films may be released from their substrates to yield free-standing membranes of thickness...

Abstract: Surface wetting on polyelectrolyte multilayers (PEMs), prepared by alternating deposition of polydiallyldimethylammonium chloride (PDDA) and poly(styrene sulfonate) (PSS), was investigated mainly in water-solid-oil systems. The surface-wetting behavior of as-prepared PEMs was well correlated to the molecular structures of the uncompensated ionic groups on the PEMs as revealed by sum frequency generation vibrational and X-ray photoelectron spectroscopies. The orientation change of the benzenesulfonate groups on the PSS-capped surfaces causes poor water wetting in oil or air and negligible oil wetting in water, while the orientation change of the quaternized pyrrolidine rings on the PDDA-capped surfaces hardly affects their wetting behavior. The underwater oil repellency of PSS-capped PEMs was successfully harnessed to manufacture highly efficient filters for oil-water separation at high flux.

Abstract: The development of simple and recyclable adsorbents with high adsorption capacity is a technical imperative for water treatment. In this work, we have successfully developed new adsorbents for the removal of ionic pollutants from water via encapsulation of polyelectrolyte complexes (PECs) made from positively charged poly(allylamine hydrochloride) (PAH) and negatively charged poly(l-3,4-dihydroxyphenylalanine) (PDopa), obtained via the self-polymerization of l-3,4-dihydroxyphenylalanine (l-Dopa). Given the outstanding mass transport through the hydrogel host matrixes, the PDopa-PAH PEC guests loaded inside can effectively and efficiently remove various ionic pollutants, including heavy metal ions and ionic organic dyes, from water. The adsorption efficiency of the PDopa-PAH PECs can be quantitatively correlated to and tailored by the PDopa-to-PAH molar ratio. Because PDopa embodies one catechol group, one carboxyl group, and one amino group in each repeating unit, the resulting PDopa-PAH PECs exhibit the ...