Structure Of Polyelectrolytes Research Articles

Effect of polyelectrolyte structure on perchlorate adsorption performance by functionalized montmorillonite

Polyelectrolyte (with different unit structure or molecular weight) modified montmorillonite (PMt) was synthesized for perchlorate (ClO4-) removal. It was found polyelectrolytes were successfully loaded on montmorillonite (Mt), and the surface potential of most PMt changed from negative to positive. Polyelectrolyte desorption on Mt was < 10 % after 48 h. Poly(diallyldimethylammonium chloride) species modified montmorillonite (PDDAx-Mt) showed excellent adsorption performance for ClO4- with maximum adsorption amount over 2.78 mmol/g and equilibrium time within 10 min. The adsorption performance of PMt toward ClO4- followed this order: PDDAx-Mt > CH-Mt > PAM-Mt > PQ28-Mt. Moreover, PDDAx-Mt and CH-Mt showed a superior adsorption selectivity to ClO4- among competitive oxyanions in the quaternary-adsorbate system (ClO4- > PO43- > SO42- > NO3–). The enhanced ClO4- adsorption could be mainly attributed to the presence of anion exchange sites (−R4N+-Cl− or –NH3+-Cl−) provided by PDDA or CH, followed by electrostatic gravitation and weak hydrogen bonding interaction. Density functional theory (DFT) calculation revealed that ClO4- adsorbed on PMt is a process of electrons transferring from O atoms in ClO4- to H atoms on C in PDDA+ or N in CH+, PAM+ and PQ28+. The preparation method of PMt is simple with excellent adsorption performance and selectivity toward ClO4-, suggesting promising applications in anion wastewater treatment.

Responses of assembled structures of block polyelectrolytes to electrostatic interaction strength.

In this paper, the responses of assembled behaviors of block polyelectrolytes (PEs) to the strength of electrostatic interactions are studied through molecular dynamic simulations. The results show that the assembled structures closely depend on the electrostatic strength. It should be noted that PE coacervation can outweigh the nucleation of hydrophobic blocks and invert the micelle structures at strong electrostatic strengths, leading to the formation of inverted micelles of PE cores and hydrophobic coronas. In the poor solvent condition for neutral block, diverse anisotropic micelles are presented; candy-like conventional micelles of hydrophobic cores and PE patches coexist with inverted candy-like micelles of PE cores and hydrophobic patches and with Janus micelles of semi-neutral aggregate and semi-PE cluster in the presence of divalent and trivalent counterions. The formation of conventional or inverted micelle is largely determined by the type of micellar fusion, which results from the nucleation competition between electrostatic correlation and hydrophobic interaction. The merge of micelles mediated by hydrophobic attraction leads to conventional hydrophobic cores, and the fusion induced by electrostatic correlations results in PE cores micelles. At strong electrostatic strengths, the PE chains exhibit rich conformations at trivalent counterions, ranging from a fully collapsed state to a rod-like state, and parallel alignment of PE chains is found.

Multivalent Ion-Mediated Polyelectrolyte Association and Structure

Multivalent Ion-Mediated Polyelectrolyte Association and Structure

Formation of compounds with diverse polyelectrolyte morphologies and nonlinear ion conductance in a two-dimensional nanofluidic channel.

Aqueous electrolytes subjected to angstrom-scale confinement have recently attracted increasing interest because of their distinctive structural and transport properties, as well as their promising applicability in bioinspired nanofluidic iontronics and ion batteries. Here, we performed microsecond-scale molecular dynamics simulations, which provided evidence of nonlinear ionic conductance under an external lateral electric field due to the self-assembly of cations and anions with diverse polyelectrolyte morphologies (e.g., extremely large ion clusters) in aqueous solutions within angstrom-scale slits. Specifically, we found that the cations and anions of Li2SO4 and CaSO4 formed chain-like polyelectrolyte structures, whereas those of Na2SO4 and MgSO4 predominantly formed a monolayer of hydrated salt. Additionally, the cations and anions of K2SO4 assembled into a hexagonal anhydrous ionic crystal. These ion-dependent diverse polyelectrolyte morphologies stemmed from the enhanced Coulomb interactions, weakened hydration and steric constraints within the angstrom-scale slits. More importantly, once the monolayer hydrated salt or ionic crystal structure was formed, the field-induced ion current exhibited an intriguing gating effect at a low field strength. This abnormal ion transport was attributed to the concerted movement of cations and anions within the solid polyelectrolytes, leading to the suppression of ion currents. When the electric field exceeded a critical strength, however, the ion current surged rapidly due to the dissolution of many cations and anions within a few nanoseconds in the aqueous solution.

A Novel Family of Stable Polyelectrolyte Complexes Based on Mixed Olefins-Maleic Anhydride Copolymer.

In the present study, the copolymer of mixed olefins included in unetherified gasoline and maleic anhydride (PUGM) was prepared by self-stabilized precipitation polymerization (2SP) and employed for the synthesis of a new family of stable polyelectrolyte complexes (PECs). Polyanionic saponified PUGM partially grafted with methoxy poly(ethylene glycol) (PUGMS-g-mPEG) and polycationic quaternized PUGM (PUGMQ) were both derived from PUGM via the facile modification of anhydride groups. The particle size, zeta potential, morphology, and stability of self-assembled PEC particles were investigated thoroughly. Strikingly, the introduction of long mPEG side chains (Mn = 4000) had a remarkable effect on the self-assembled particles, which displayed a constant particle size of ∼200 nm regardless of varying n+/n-. Moreover, it also enhanced the salt tolerance and long-term stability of PEC particles significantly. Our work not only provides an effective approach to PECs from petroleum resources with low cost but also deepens the understanding of the relationship between the chain structure of polyelectrolytes and the stability of PECs.

Rearrangements in the Conformational Structure of Polyelectrolytes on the Surface of a Flattened Metal Nanospheroid in an Alternating Electric Field

Rearrangements in the Conformational Structure of Polyelectrolytes on the Surface of a Flattened Metal Nanospheroid in an Alternating Electric Field

Rethinking nucleic acids from their origins to their applications.

Reviewed are three decades of synthetic biology research in our laboratory that has generated alternatives to standard DNA and RNA as possible informational systems to support Darwinian evolution, and therefore life, and to understand their natural history, on Earth and throughout the cosmos. From this, we have learned that: • the core structure of nucleic acids appears to be a natural outcome of non-biological chemical processes probably in constrained, intermittently irrigated, sub-aerial aquifers on the surfaces of rocky planets like Earth and/or Mars approximately 4.36 ± 0.05 billion years ago; • however, this core is not unique. Synthetic biology has generated many different molecular systems able to support the evolution of molecular information; • these alternatives to standard DNA and RNA support biotechnology, including DNA synthesis, human diagnostics, biomedical research and medicine; • in particular, they support laboratory in vitro evolution (LIVE) with performance to generate catalysts at least 104-105 fold better than standard DNA libraries, enhancing access to receptors and catalysts on demand. Coupling nanostructures to the products of LIVE with expanded DNA offers new approaches for disease therapy; and • nevertheless, a polyelectrolyte structure and size regular building blocks are required for any informational polymer to support Darwinian evolution. These features serve as universal and agnostic biosignatures, useful for seeking life throughout the Solar System. This article is part of the theme issue 'Reactivity and mechanism in chemical and synthetic biology'.

Efficient Synthesis of High-Performance Anion Exchange Membranes by Applying Clickable Tetrakis(dialkylamino)phosphonium Cations.

Tetrakis(dialkylamino)phosphonium (TKDAAP) compounds exhibit extraordinary base resistance, a prerequisite feature for high-performance anion exchange membranes (AEMs). It is, however, challenging to synthesize a TKDAAP compound with reactive functionality that can be used to link the cation to a polymer backbone. In this study, two TKDAAP compounds with alkyne functionality were synthesized and incorporated into an azide-modified SBS triblock copolymer backbone via Cu(I)-catalyzed alkyne-azide cycloaddition (CuAAC) "click" chemistry. The properties of the resulting AEMs were characterized. It was found that (1) the triazole linker between the cation and the polymer backbone was stable under alkaline conditions; (2) varying the substituents of TKDAAP compounds could dramatically alter the stability; and (3) increasing the hydrophilicity of the AEM was an efficient way to enhance its ionic conductivity. Using clickable TKDAAP compounds makes it easy to combine various cations into polymer backbones with adjustable cation content, thus potentially leading to an efficient way to screen a wide variety of polyelectrolyte structures to identify the most promising candidates for high-performance AEMs.

Insights into Extended Structures and Their Driving Force: Influence of Salt on Polyelectrolyte/Surfactant Mixtures at the Air/Water Interface.

This paper addresses the effect of polyelectrolyte stiffness on the surface structure of polyelectrolyte (P)/surfactant (S) mixtures. Therefore, two different anionic Ps with different intrinsic persistence length lP are studied while varying the salt concentration (0-10-2 M). Either monosulfonated polyphenylene sulfone (sPSO2-220, lP ∼20 nm) or sodium poly(styrenesulfonate) (PSS, lP ∼1 nm) is mixed with the cationic surfactant tetradecyltrimethylammonium bromide (C14TAB) well below its critical micelle concentration and studied with tensiometry and neutron reflectivity experiments. We kept the S concentration (10-4 M) constant, while we varied the P concentration (10-5-10-3 M of the monomer, denoted as monoM). P and S adsorb at the air/water interface for all studied mixtures. Around the bulk stoichiometric mixing point (BSMP), PSS/C14TAB mixtures lose their surface activity, whereas sPSO2-220/C14TAB mixtures form extended structures perpendicular to the surface (meaning a layer of S with attached P and additional layers of P and S underneath instead of only a monolayer of S with P). Considering the different P monomer structures as well as the impact of salt, we identified the driving force for the formation of these extended structures: compensation of all interfacial charges (P/S ratio ∼1) to maximize the gain of entropy. By increasing the flexibility of P, we can tune the interfacial structures from extended structures to monolayers. These findings may help improve applications based on the adsorption of P/S mixtures in the fields of cosmetic or oil recovery.

Nano-Sized Polyelectrolyte Complexes Formed between Poly(vinyl benzyl trimethyl ammonium chloride) and Insulin

Novel biohybrid homo-polyelectrolyte-based nanocarriers were formed by the complexation of insulin (INS) with a biocompatible and cationic polyelectrolyte, namely, poly(vinyl benzyl trimethylammonium chloride) (PVBTMAC). According to light-scattering techniques, the hydrophilic PVBTMAC homo-polyelectrolyte forms single chains in aqueous media. The resulting biohybrid PVBTMAC/INS nanocarriers were formed via electrostatic co-assembly. The effects of polyelectrolyte structure and content on the characteristics of the formed PVBTMAC/INS complexes were studied. A significant aggregation tendency of the PVBTMAC/INS complexes was observed, based on the physicochemical results, especially at high protein concentration, corroborating the effective electrostatic interaction of INS with the cationic polyelectrolyte. The physicochemical properties of the formed PVBTMAC/INS nanocarriers depended on the concentration of the stock polymer and INS solutions. A neat PVBTMAC homo-polymer and PVBTMAC/INS nanocarriers demonstrated good serum stability in the presence of fetal bovine serum (FBS) proteins. Fluorescence spectroscopy (FS) studies revealed no INS conformational changes after its complexation with the cationic PVBTMAC polyelectrolyte. The obtained PVBTMAC/INS complexes demonstrated considerable and promising characteristics for potential use as insulin delivery systems.

Effects of Salt Aggregation in Perfluoroether Electrolytes

Electrolytes comprised of polymers mixed with salts have great potential for enabling the use of Li metal anodes in batteries for increased safety. Ionic conductivity is one of the key performance metrics of these polymer electrolytes and achieving high room-temperature conductivity remains a challenge to date. For a bottom-up design of the polymer electrolytes, we must first understand how the structure of polyelectrolytes on a molecular level determines their properties. Here, we use classical molecular dynamics to study the solvation structure and ion diffusion in electrolytes composed of a short-chain perfluoroether with LiFSI or LiTFSI salts. Density functional theory is also used to provide some insights into the structures and energies of the salt interactions with the perfluoroether. We observe the formation of aggregates of salts in the fluorinated systems even at low salt concentrations. The fluorine-fluorine attraction in the solvent is the governing factor for creating the salt aggregates. The aggregates’ size and lifetime change with concentration and anion. These simulations provide an insight into the structure and dynamics of perfluoroether based electrolytes that can be used to improve Li-ion batteries.

Regulated Polyion Complex Vesicles for Efficient Photothermal Therapy

AbstractPolyion complex (PIC) vesicles have attracted considerable attention as soft yet functional delivery vehicles. However, most of the PIC vesicles suffer from insufficient stability and functionality which hinder their applications. Herein, a new type of PIC vesicles obtained by co‐assembly of neutral‐cationic diblock copolymers with a supramolecular coordination polyelectrolyte is reported. The latter exhibits tunable structures and properties that endows regulated stability and functionalities of the vesicles. With lanthanide‐based coordination polymers, PIC vesicles are constructed with not only enhanced stability against salt, but also tunable fluorescent or magnetic properties associated with particular Ln3+ ions. Moreover, the vesicle lumen is applied to load PEGlated indocyanine green as a model photothermal transduction agent. The designed vesicles finally display high stability, good biocompatibility, and efficient photothermal conversion, and therefore behave well for thermal ablation of both tumor cells and tumor in mice. The well‐regulated stability and functions of the PIC vesicles are assigned the adaptive structure and properties of the supramolecular coordination polyelectrolytes, which hardly be achieved with conventional covalent polyelectrolytes. This study therefore demonstrates a facile strategy to regulate the stability and function of PIC vesicles, and shall be inspirational for developing novel vesicular materials for potential biomedical applications.

Structures of cationic and anionic polyelectrolytes in aqueous solutions: the sign effect.

In this study, we use molecular dynamics simulation to explore the structures of anionic and cationic polyelectrolytes in aqueous solutions. We first confirm the significantly stronger solvation effects of single anions compared to cations in water at the fixed ion radii, due to the reversal orientations of asymmetric dipolar H2O molecules around the ions. Based on this, we demonstrate that the solvation discrepancy of cations/anions and electrostatic correlations of ionic species can synergistically cause the nontrivial structural difference between single anionic and cationic polyelectrolytes. The cationic polyelectrolyte shows an extended structure whereas the anionic polyelectrolyte exhibits a collapsed structure, and their structural differences decline with increasing the counterion size. Furthermore, we corroborate that multiple cationic polyelectrolytes or multiple anionic polyelectrolytes can exhibit largely differential molecular architectures in aqueous solutions. In the solvation dominant regime, the polyelectrolyte solutions exhibit uniform structures; whereas, in the electrostatic correlation dominant regime, the polyelectrolyte solutions exhibit heterogeneous structures, in which the likely charged chains microscopically aggregate through counterion condensations. Increasing the intrinsic chain rigidity causes polyelectrolyte extension and hence moderately weakens the inter-chain clustering. Our work highlights the various, unique structures and molecular architectures of polyelectrolytes in solutions caused by the multi-body correlations between polyelectrolytes, counterions and asymmetric dipolar solvent molecules, which provides insights into the fundamental understanding of ion-containing polymers.

Fundamentals and mechanics of polyelectrolyte gels: Thermodynamics, swelling, scattering, and elasticity

Polyelectrolyte gels are ionizable, crosslinked polymer networks swollen in a solvent. These materials are prevalent in biological and synthetic applications ranging from the extracellular matrix to personal care products because they swell and deswell according to changes in the solution environment and internal structure. These environmental and internal factors include temperature, solvent, salt, pH, polymer volume fraction, and crosslink density. In order to predict useful properties like swelling and modulus, 70+ years of effort have been taken to understand the thermodynamic driving forces that affect polyelectrolyte gels. Here, we consider the current thermodynamic model of polyelectrolyte gel behavior, which includes balancing the mixing, electrostatic, Donnan, and elastic osmotic pressures, and we present current experimental results in the context of this model. Since the internal free energy of polyelectrolyte gels results in structural and modulus changes, we also review how thermodynamics are linked to rheological and scattering studies. Due to the complex nature of polyelectrolyte gels, the influence of the solution environment on gel behavior and structure has been investigated; however, the current findings are convoluted with multiple equilibrium states and there is a need for greater understanding of the influence of counterion condensation, interfaces, and inhomogeneities. By describing the current state of the thermodynamic model for polyelectrolyte behavior, we emphasize the complexity and tunability of polyelectrolyte gels for future applications. We propose the future direction of polyelectrolyte gel research to focus on gels at interfaces, in human biology, and on gel inhomogeneities. However, these future directions require an understanding of polyelectrolyte gel mechanical properties, structure, and complex nature that can be understood using the current thermodynamic model.

Hole transporting electrodeposited PEDOT–polyelectrolyte layers for perovskite solar cells

Thin layers of poly(3,4-ethylenedioxythiophene) complexes with various sulfonated polyelectrolytes were formed electrochemically in a galvanostatic regime. These transparent hole transport layers were used in CH3NH3PbI3 perovskite solar cells and the influence of the polyelectrolyte structure on the device performance was featured.

New insight in the operation mechanism of Organic Memristive Devices: The role of PEO-based polyelectrolyte solute ions

The operation mechanism of polyaniline-based Organic Memristive Devices, synapse-like devices particularly important for neuromorphic applications, are further investigated to better clarify their principle of operation and in view of improving their performance, stability and reliability. In this framework, even though they have been studied extensively in the past, aspects of their operation mechanism require a better understanding. In earlier studies, an important role in terms of the promotion of device switching is attributed to lithium ions present in polyethylene oxide (PEO), which serves as the solid polyelectrolyte (SPE). In a recent work, the role of dopant ions as well as the material of the gate electrode have been assessed, suggesting that it is the chloride ions and silver, respectively, that are relevant for the system's memristive switching. The present paper further investigates the role of the solute ions in devices with various polyethylene oxide-based polyelectrolytes. In a series of experiments using a number of different polyelectrolyte dopant salts, we provide additional evidence that cations have no decisive effect on the memristive switching of the device, while the nature of the dopant anion, on the contrary, plays a crucial role. Moreover, giving an improved insight about the effects of the dopant in the SPE, this study shows that the polyelectrolyte is crucial for the performance of the device. To this end, it is shown that in addition to the hygroscopicity of the salt additive, it is quite important to consider also the lyotropicity of its ions to establish a favourable SPE structure. The results of our study provide a deeper understanding of the factors that cause the device's degradation and suggest novel approaches to improve stability, performance and endurance of the solid polyelectrolyte-based Organic Memristive Device. • Solid polyelectrolyte dopant cations play no significant role in OMD switching. • Lithium ions can be replaced by any other SPE dopant cation. • The nature of the dopant anion is crucial for the operation mechanism of OMD. • Hygroscopic and lyotropic salts provide favourable solid polyelectrolyte structure.

Spatial segregation of mixed-sized counterions in dendritic polyelectrolytes

Langevin dynamics simulations are utilized to study the structure of a dendritic polyelectrolyte embedded in two component mixtures comprised of conventional (small) and bulky counterions. We vary two parameters that trigger conformational properties of the dendrimer: the reduced Bjerrum length, lambda _B^*, which controls the strength of electrostatic interactions and the number fraction of the bulky counterions, f_b, which impacts on their steric repulsion. We find that the interplay between the electrostatic and the counterion excluded volume interactions affects the swelling behavior of the molecule. As compared to its neutral counterpart, for weak electrostatic couplings the charged dendrimer exists in swollen conformations whose size remains unaffected by f_b. For intermediate couplings, the absorption of counterions into the pervaded volume of the dendrimer starts to influence its conformation. Here, the swelling factor exhibits a maximum which can be shifted by increasing f_b. For strong electrostatic couplings the dendrimer deswells correspondingly to f_b. In this regime a spatial separation of the counterions into core–shell microstructures is observed. The core of the dendrimer cage is preferentially occupied by the conventional ions, whereas its periphery contains the bulky counterions.

IMPLEMENTATION OF THE DРIE METHOD IN TECHNOLOGIES OF OBTAINING STRUCTURED SYSTEMS

Within the framework of the work, experimental and laboratory studies of a complex of heat and mass transfer processes in multicomponent disperse systems that exhibit emergent properties have been carried out.&#x0D; The aim of the work is to determine the key factors that affect the properties of the final product, and bifurcation points for complex dispersed systems in terms of the mechanisms of structure formation.&#x0D; The authors determined the influence of key parameters such as the process temperature and shear stresses that arise in systems during processing in rotary-pulsating devices of the disk-cylindrical type.&#x0D; For systems with polyelectrolyte structures, the temperature ranges have been determined at which the intensity of the solvation process is maximum.&#x0D; The investigated multicomponent systems are sensitive to shear stress and the duration of its exposure. The limiting shear stresses are determined at which the destruction of structures begins and the system becomes fluid.&#x0D; Based on the results of the complex of works, a schematic diagram and a pilot plant for obtaining poly-component structured systems were proposed. Вatches of bactericidal sanitary-hygienic means and application medical-prophylactic means were obtained at the proposed installation and transferred for testing.

Physicochemical features assessment of acemannan-based ternary blended films for biomedical purposes

The exploitation of natural origin macromolecules, as complex physical mixtures or drugs, increases in biomedical or tissue engineering (TE) solutions. Aloe Vera is a highly explored medicinal plant, from which the main polysaccharide is acemannan (ACE). The ACE combination with chitosan and alginate results in interactions that lead to mixed junction zones formation, predicting membrane functionality improvement.This work proposes the development and characterization of ACE-based blended films as a promising strategy to design a nature-derived bioactive platform.The results confirmed that stable complex polyelectrolyte structures were formed through different intermolecular interactions. The films present good dimensional stability, flexibility, an adequate swelling ability with mostly radial water uptake, and a sustainable ACE release to the medium. Positive biological performance of the ACE-based blended films with L929 cells also suggested that they can be applied in TE solutions, with the potential to act as bioactive topical platforms.

Нитрон талшығы қалдықтарының негізінде к-30 қасиеттерін зерттеу

The purpose of the work is study the structure of polyelectrolytes for obtaining of hydrogels for water-retention in sandy soil of Aral region.To study the time of hydrolysis of nitron fiber waste and the IR spectra of the materials obtained. Thus, a method for producing hydrogels based on hydrolyzed OVN and polyvalent metal salts has been developed. The crosslink density of macromolecules is determined by the concentration of the polymer. There are shown dynamics of changes in the structural and mechanical characteristics in the process of gelation.