Polyelectrolyte Effect Research Articles

Effect of polyelectrolytes and polyelectrolyte mixtures on the electrokinetic potential of dispersed particles. 2. Electrokinetic potential of silica particles in electrolyte, polyelectrolyte and polyelectrolyte mixtures solutions

The effect pH, ionic strength (KCl concentration), weakly and medium charged anionic and cationic polyelectrolytes (PEs) as well as their binary mixtures on the electrokinetic potential of silica particles as a function of the polyelectrolyte/mixture dose, its composition, charge density (CD) of the PE, and way of adding the polymers to the suspension has been studied. It has been shown that addition of increasing amount of anionic PEs increases the absolute value of the negative zeta-potential of particles at pH > pH isoelectric point (IEP = 2.5); this increase is stronger the charge density of the polyelectrolyte is higher. Adsorption of cationic polyelectrolytes at these pH values gives a significant decrease in the negative ζ-potential and overcharging the particles; changes in the ζ-potential are more pronounced for PE samples with higher CD. In mixtures of cationic and anionic PE at pH > pHIEP, the ζ-potential of particles is determined by the adsorbed amount of the anionic polymer independently of the CD of PEs, the mixture composition and the sequence of addition of the mixture components. Unexpectedly, the ζ-potential of silica at pH = 2.1, i.e. < pHIEP, turned out to be positive in the presence of both anionic PE and cationic + anionic PE mixtures. This is explained by formation (and adsorption onto positively charged silica surface) of pseudo-cationic PEs from anionic ones due to transfer of protons from the solution to the amino-group of the anionic polymer. Considerations about the role of coulombic and non-coulombic forces in the mechanism of PE adsorption are presented.

Effect of Polyelectrolytes and Polyelectrolyte Mixtures on the Electrokinetic Potential of Dispersed Particles. 2. Electrokinetic Potential of Silica Particles in Electrolyte, Polyelectrolyte and Polyelectrolyte Mixtures Solutions

Effect of Polyelectrolytes and Polyelectrolyte Mixtures on the Electrokinetic Potential of Dispersed Particles. 2. Electrokinetic Potential of Silica Particles in Electrolyte, Polyelectrolyte and Polyelectrolyte Mixtures Solutions

Effect of Polyelectrolytes and Polyelectrolyte Mixtures on the Electrokinetic Potential of Dispersed Particles. 1. Electrokinetic Potential of Polystyrene Particles in Solutions of Surfactants, Polyelectrolytes and Their Mixtures

Effect of Polyelectrolytes and Polyelectrolyte Mixtures on the Electrokinetic Potential of Dispersed Particles. 1. Electrokinetic Potential of Polystyrene Particles in Solutions of Surfactants, Polyelectrolytes and Their Mixtures

83 Application of differential scanning calorimetry to measure the differential binding of ions, water, and protons in the unfolding of DNA molecules

The overall stability of DNA molecules globally depends on base-pair stacking, base pairing, polyelectrolyte effect, and hydration contributions. In order to improve our understanding of the role of ions, water, and protons in the stability and melting behavior of DNA structures, we report an experimental approach to determine the differential binding of ions (Δn ion), water (Δn W), and protons (Δn H+) in the helix-coil transition of DNA molecules. A combination of differential scanning calorimetry (DSC) and temperature-dependent UV and CD spectroscopic techniques to investigate the unfolding of a variety of DNA molecules: S.T. DNA, two dodecamers, one undecamer, nine short hairpins as a function of the GC content of their stem, and two triplexes. We determine complete thermodynamic profiles, including all the three linking numbers, for the unfolding of each molecule. The CD spectra indicated that all molecules adopted the B-conformation at low temperatures. Thermodynamic profiles obtained from the DSC curves indicate that the favorable folding of each molecule results from the typical compensation of favorable enthalpy and unfavorable entropy contributions, and negligible heat capacity effects. UV and DSC melting curves as a function of salt, osmolyte, and proton concentrations yielded releases of ions, water, and protons (for the triplex with C+GC base triplets). Therefore, the favorable folding of each DNA molecule results from the formation of base-pair stacks and uptake of water and counterions. The thermodynamic data will be discussed in terms of the effects of DNA length, loop contributions and type of water molecules.

Dissolution of DNA and F-Actin Bundles Stabilized by Polyelectrolyte Effects

When intracellular anionic polyelectrolyte filaments are released into the extracellular space due to cell damage, they are exposed to polyvalent cations such as antimicrobial peptides and other multications present in extracellular fluids. As a result, these filaments form large bundles stabilized by electrostatic interactions that cause a variety of pathologic states, including an abnormal increase in viscosity and elastic moduli in airway fluids and sputum from patients with respiratory disease.DNase has long been used as a therapeutic treatment to fluidize sputum in cystic fibrosis patients, but its effectiveness in some cases is limited by the presence of other polyelectrolytes such as F-actin and the inability to access large dense DNA bundles before the enzyme is inactivated by proteases. Polyelectrolyte theories suggest that DNA and F-actin bundles can also be destabilized by addition of small soluble co-anions such as oligo-aspartate that potentially could act additively or synergistically to promote the depolymerizing effects of DNase on DNA bundles or gelsolin on F-actin bundles. We have analyzed approximately 100 sputum samples from cystic fibrosis patients to document their DNA and F-actin content, their elastic and viscous parameters and their susceptibility to fluidization by DNase, gelsolin, and oligo-aspartate. We show a significant benefit of adding oligo-aspartate on the ability of DNase-1 to reduce the abnormally high shear modulus of CF sputum. The ability of oligo-aspartate and DNase-1 to reduce sputum stiffness strongly correlates with the amount of DNA present in the sputum and is further modulated by the co-mingling of DNA and F-actin. These studies suggest that the principles of polyelectrolyte theory are relevant to the formation of filament bundles in a complex biological fluid and that they can guide production of more effective methods to disrupt the formation of abnormal biopolymer assemblies.

Structure of pH sensitive self-assembled amphiphilic di- and triblock copolyelectrolytes: micelles, aggregates and transient networks

We have studied the self-assembly of aqueous dispersions of amphiphilic di- and triblock copolyelectrolytes using static and dynamic light scattering. The hydrophobic blocks contained both ionisable and hydrophobic units rendering the association dynamic and thus ensuring that thermodynamic equilibrium was reached. The incorporation of ionisable units into the hydrophobic blocks caused the self-assembly to be strongly influenced by the pH and the ionic strength. As in the case of neutral block copolymers, diblock copolyelectrolytes self-assembled into star-like micelles and triblock copolyelectrolytes formed flower-like micelles. The latter was not predicted to occur for block copolyelectrolytes. At higher concentrations a system spanning network was formed. The structure of the systems could be quantitatively described by a model of purely repulsive spheres for the diblocks and attractive spheres for the triblocks. The polyelectrolyte effect expressed itself by a sensitivity of the structure to the pH and the ionic strength. The attraction increased with decreasing pH and increasing ionic strength leading at high ionic strength to phase separation.

Effect of Dispersant Agent Amount in Colloidal Processing of Zirconia Dental Ceramic

The effects of a polyelectrolyte dispersant agent, polyethyleneimine (PEI), on the rheology of zirconia 3Y-TZP suspensions and the densification characteristics of sintered zirconia were investigated. The colloidal processing technique was used to minimize the agglomeration of nanoparticles during the fabrication of the samples. Five batches of 10% zirconia suspensions containing different amounts of PEI at 0.3, 0.4, 0.5, 0.6, and 0.7 wt% were prepared. The rheological properties of the zirconia suspensions were determined using a rotational viscometer. The optimum amount of PEI that can maximize powders dispersion was determined. The green samples were then prepared using the slip casting process. The samples were densely sintered at a final sintering temperature of 1300 °C. The result revealed that the zirconia suspension with 0.5 wt% PEI was the most optimum amount to obtain a well-dispersed suspension. The sintered density of zirconia 3Y-TZP reached its maximum by adding 0.5 wt% PEI.

Influence of triphenylphosphonium pendant groups on the rheological and morphological properties of new quaternized polysulfone

A new quaternized polysulfone with triphenylphosphonium pendant groups was synthesized by reacting chloromethylated polysulfone with triphenylphosphine. The molecular restructurations, generated by hydrogen bonding, electrostatic interactions, and association phenomena in ternary quaternized polysulfone/N,N-dimethylformamide (solvent)/water (nonsolvent) systems, were evaluated by rheological investigations. The polyelectrolyte effect, induced by enhanced dissociation of the ionizable groups and by mixed solvents' quality, modify the rheological functions, that is, dynamic viscosity, elastic shear modulus, and viscous shear modulus, as well as the thermodynamic parameters obtained from the rheological properties, such as apparent activation energy. These results were correlated with the morphological properties of the films obtained from solutions in solvent/nonsolvent mixtures and compared with other quaternized polysulfones, having different hydrophobic characteristics. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Effect of an Anionic Polyelectrolyte Adsorption on the Colloidal Stability of Aqueous 3Y-TZP Suspensions

The effects of an anionic polyelectrolyte on the dispersion of 3Y-TZP suspensions in aqueous medium have been systematically investigated. The results of rheological experiments show that at CD = 0.5 wt% (CD : dispersant concentration), the dispersant could afford well-dispersed 3Y-TZP suspensions over a wider range of solids loading, owing to the stronger electrostatic repulsion between particles resulting from the monolayer coverage of the particle. But as CD ≤ 0.5 wt% or CD ≥0.5 wt%, the stable 3Y-TZP suspensions can only be achieved at a relatively lower solids loading, which are ascribed to the reduced repulsion barrier between particles owing to the lower ζ values of particles and the higher ionic strength in the system, respectively.

Polyelectrolyte effects on the crystallization phenomena of the lithium carbonate

Anionic polyelectrolyte effects on the lithium carbonate crystallization phenomena were investigated. Li2CO3 crystals were obtained by reactive crystallization with seed crystals. Polyelectrolytes were dissolved into the reactive field before the reaction. Obtained crystals were observed with scanning electron microscopy (SEM) and crystal size and agglomeration degree were measured by the SEM images. The results show that Li2CO3 crystallized different shape and size from absence of polyelectrolyte in those reactive fields. Especially polyacrylic acid (PAA) improved on the agglomeration of the crystals and shaped them high aspect needles. Thus other experimental conditions including PAA molecular weight and concentration, reaction time, supersaturation by Li concentration were investigated in addition. As a result, obtained crystals were not different in each PAA molecular weight reactive fields. Meanwhile PAA concentration has optimum range. Li2CO3 formed less agglomeration and higher aspect around 1g/l. In the concentration, Li2CO3 did not agglomerate regardless of aging time and Li concentration. Moreover crystals became rectangle shape in higher Li concentration.(020) face intensity of the rectangle shape crystals increased according to XRD pattern. PAA affected the facial growth. These results may provide a method of morphological change and clearly crystallization of Li2CO3.

CTST-21: A Phase 2, Randomized, Double-Blind, Multi-Center Study Comparing 15G Cross-Linked Polyelectrolyte (CLP) versus Placebo in Heart Failure Patients with Chronic Kidney Disease

The goal of this double-blind, randomized, placebo-controlled trial was to evaluate the effects of a cross-linked polyelectrolyte (CLP) on serum potassium and measures of congestion in patients with heart failure (HF) and chronic kidney disease (CKD). The pre-specified primary endpoint was change in serum K+ over time, with an associated goal of facilitating the initiation of aldosterone blockers in patients at risk for hyperkalemia. Since CLP also removes fluid through the GI tract, we also hypothesized that this intervention would ameliorate congestion as assessed by serial weights and its associated symptoms, as assessed by NYHA class, quality of life (assessed by the Kansas City Cardiomyopathy Questionnaire (KCCQ), and 6 minute walk test (6MWT) after 8 weeks of CLP treatment.

Effect of polyelectrolytes on the degree of flocculation of papermaking suspensions

The effects of the surface charge type and density of polyacrylamides (PAMs) on the turbidity reduction, zeta potential, settling rates, floc sizes and effective floc density of papermaking suspensions were investigated at different pH values. Cationic C496 and C492, anionic A130LMW and non-ionic N130 PAMs were used in this study. At optimum dosage, anionic A130LMW PAM proved to be the most effective in the residual turbidity reduction among other PAMs investigated in this work. In contrast, the non-ionic N130 polyacrylamide showed an adverse effect on the degree of flocculation. On the other hand, the floc sizes were larger in the presence of the anionic PAM than the cationic PAMs due to the repulsive forces between the anionic PAM and particle surface, leading to the formation of open structure flocs of less effective density. The results also show that increasing the cationic surface charge from 10% to 35% reduces the floc size and increases the effective floc density. This work has been very successful in establishing the link between electrokinetic behaviour and the produced floc effective density for the flocculated papermaking-PAM suspensions.

Structure–rheology relationship in complex quaternized polysulfones/solvent/nonsolvent systems

Polymer chains consisting of water-soluble polysulfones with various amounts of ionic chlorine have been prepared via the quaternization reaction of chloromethylated polysulfones with N,N-dimethylethanolamine. Rheological investigations have reflected the importance of electrostatic interactions, hydrogen bonding, and association phenomena from the ternary systems consisting of a proton-acceptor polymer (polysulfones with different ionic chlorine content), a proton-donor solvent (N,N-dimethylformamide), and a proton-donor solvent (methanol). The specific interactions, the polyelectrolyte effect induced by enhanced dissociation of the ionizable groups and mixed solvents’ quality modify the rheological functions, i.e., dynamic viscosity, elastic shear modulus and viscous shear modulus, as well as the thermodynamic parameters obtained from the rheological properties, such as apparent energy of activation and flow activation entropy. These results were correlated with the surface properties of the polysulfonic films formed from solutions in solvent/nonsolvent mixtures.

Determination of absolute molecular weight of sodium lignosulfonates (NaLS) by laser light scattering (LLS)

Abstract The problems related to the determination of the absolute molecular weight (M w) of sodium lignosulfonate (NaLS) are the focus of the present work. Four narrow-dispersed NaLS fractions were collected by filtration, ultrafiltration, and gel permeation chromatography (GPC), and their M w measured by laser light scattering (LLS Mw ) was compared with that obtained by GPC (GPC Mw ). The LLS Mw values were much larger than GPC Mw , and this M w difference increased with increasing M w of NaLS. This finding confirms the known polyelectrolyte and aggregation effects of NaLS. The deviation is also partly due to the conformation differences between the GPC standard (sodium polystyrene sulfonate) and the NaLS molecules. The effects of polyelectrolytes and NaLS aggregates could be inhibited by adding enough NaCl salt in the NaLS solution and filtering the NaLS/NaCl solution through a syringe filter. As a result, the slow mode in dynamic LLS measurement disappeared. By this approach, the absolute LLS Mw values were only slightly larger than that determined by GPC due to the conformation differences between the GPC standard and the NaLS molecules.

Facile preparation of hierarchical porous carbons with tailored pore size obtained using a cationic polyelectrolyte as a soft template

Hierarchical porous carbons (HPCs) were obtained by carbonization of resorcinol-formaldehyde (RF) gels prepared in the presence of a cationic polyelectrolyte as a soft template. The porosity of the gels is maintained during air drying due to the stabilizing effect of a cationic polyelectrolyte on the sol–gel nanostructure. The proposed method greatly simplifies the production of porous carbon by making it unnecessary to use complex drying procedures, cumbersome solvent exchanges, and long curing times. Additionally, pore size of the HPCs can be tailored (from mesoporous to macroporous range) by controlling the amount of polyelectrolyte in the initial stage of RF polymerization. The HPCs have a high specific surface area (up to 675m2/g), large specific capacitance (up to 140F/g) and areal capacitance (up to 0.1F/cm2), in acidic media. Significantly retention of the specific and areal capacitances of 72% are observed at high scan rates of 200mV/s, making it suitable as an active material for fast supercapacitor applications.

Flocculative clarification of natural and industrial turbid waters in the of presence carboxide-, amide-, amine containing polyelectrolytes

The higher flocculation and clarification effect of polyelectrolytes 4-VP∙НСl:АА-3, 2-М-5-VP∙НСl:АА-3 и МAАА-3-Н compared with PAA and aluminum sulfate has been stated. The revealed distinctions are caused by different density, quantitative correlation, nature, charge sign and dissociative ability and availability of quarternized nitrogen in the composition of functional groups as well.

A double‐blind, randomized, parallel, placebo‐controlled study examining the effect of cross‐linked polyelectrolyte in heart failure patients with chronic kidney disease

This double-blind, randomized, parallel, placebo-controlled investigation evaluated the effects of cross-linked polyelectrolyte (CLP) on serum potassium and measures of congestion in patients with heart failure (HF) and chronic kidney disease (CKD). The primary endpoint was change in serum potassium over time. Exploratory endpoints included: weight, physician and patient assessment of exertional dyspnoea, effect on N-terminal pro brain natriuretic peptide (NT-proBNP) levels, New York Heart Association (NYHA) classification, 6 min walk test (6MWT), and quality of life by Kansas City Cardiomyopathy Questionnaire (KCCQ). Serum potassium was similar in CLP (n =59) and placebo (n =52) groups throughout the 8-week study. Weight loss was greater in the CLP than in the placebo group at Weeks 1 (P =0.014) and 2 (P =0.004), and this trend continued until the end of the study. After 8 weeks, by physician assessment, the percentage of patients experiencing marked or disabling dyspnoea tended to be lower in the CLP than in the placebo group (7.3% vs. 23.9%, P =0.128). Fewer patients in the CLP than in the placebo group had NT-proBNP levels >1000 pg/mL at Week 4 (P =0.039) and Week 8 (P =0.065). The proportion of patients improving by at least one NYHA functional class over the study was higher in the CLP than in the placebo group (48.8% vs. 17.4%; P =0.002). Effects on 6MWT at Week 8 (p =0.072) and quality of life (overall KCCQ score) at Week 4 (p =0.005) and 8 (P =0.062) all favoured the CLP cohort. Four treatment-unrelated deaths occurred in the CLP group and none in the placebo group (P =0.056). In advanced, symptomatic HF with CKD, CLP is associated with beneficial clinical effects without significant serum potassium changes. NCT01265524.

Polyelectrolyte complex nanoparticles from chitosan and poly(acrylic acid) and Polystyrene‐block‐poly(acrylic acid)

AbstractInterpolymer polyelectrolyte complexes of chitosan (CS) with poly(acrylic acid) homopolymers and polystyrene‐block‐poly(acrylic acid) diblock copolymers were prepared and characterized. The influence of the positive/negative charge balance (charge ratio), pH, and ionic strength were thoroughly studied by dynamic light scattering. The existence of a strong polyelectrolyte effect was also highlighted in this study. Domains of stability, in which nanoparticle sizes are smaller than 100 and 200 nm for complexes of CS with the homopolymer and copolymer, respectively, were identified and confirmed by scanning electron microscopy and atomic force microscopy. The charged nature of the surface of the nanoparticles was evidenced by Zeta potential measurements. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

On the origin of the unusual behavior in the stretching of single-stranded DNA

Force-extension curves (FECs), which quantify the response of a variety of biomolecules subject to mechanical force (f), are often quantitatively fit using worm-like chain (WLC) or freely jointed chain (FJC) models. These models predict that the chain extension, x, normalized by the contour length increases linearly at small f and at high forces scale as x ~ (1 - f(-α)), where α = 0.5 for WLC and unity for FJC. In contrast, experiments on single-stranded DNA (ssDNA) show that over a range of f and ionic concentration, x scales as x ~ ln f, which cannot be explained using WLC or FJC models. Using theory and simulations we show that this unusual behavior in FEC in ssDNA is due to sequence-independent polyelectrolyte effects. We show that the x ~ ln f arises because in the absence of force the tangent correlation function, quantifying chain persistence, decays algebraically on length scales on the order of the Debye length. Our theory, which is most appropriate for monovalent salts, quantitatively fits the experimental data and further predicts that such a regime is not discernible in double-stranded DNA.

Influence of polyelectrolytes on crystallization of zeolite Y

In this study, the influence of polyelectrolytes on the crystallization of zeolite Y is investigated. The prepared synthesis mixtures are aged at room temperature for 24h and then left to crystallize. The compositional and structural information are provided by elemental analysis obtained by ICP, X-ray diffraction spectroscopy (XRD), scanning electron microscopy (SEM), particle size analyzer and adsorption and desorption isotherms of nitrogen by a volumetric adsorption instrument. The first group of synthesis studies is conducted by using solutions containing no additive (WA), nonionic (NI), 100% anionic (100A), and 100% cationic (100C) polyelectrolytes. The crystallization temperature and crystallization time are kept at 100ºC and 48h, respectively. The experimental results show that nonionic polyelectrolyte has the most influence on the crystallization of zeolite NaY. In the second group of synthesis studies, the effects of polyelectrolytes with various degrees of anionic properties (10%, 50% and 70%) of the same chemical structure are investigated by conducting crystallization experiments at 100°C for a duration of 48h. The results suggest that; particle size, crystallinity and BET surface area (SBET) can be controlled by adding anionic polyelectrolytes to the solution.