Heteropoly Anion Research Articles

Speciation of the Oxide Phase of Molybdenum‐Based HDS Catalysts Enhanced with Organic Additives Using an EXAFS/Raman Coupling Methodology

AbstractThe ability to gain access to the speciation of hydrodesulfurization (HDS) catalysts used for removing sulfur and nitrogen from transportation fuels is becoming a key feature in the understanding and improvement of their catalytic activity with the aim of reducing greenhouse gas emissions of fossil fuels. A novel coupling methodology between Raman spectroscopy and X‐ray absorption spectroscopy (XAS) was developed, which allows for precise qualitative and quantitative analysis of the oxide phase of Mo‐based catalysts. This enabled the detailed study of various impregnation parameters and the characterization of HDS catalysts before sulfidation. To illustrate this methodology, the effects of two additives (triethylene glycol and citric acid) were studied. The results demonstrated that organic additives exert a profound influence on the speciation of oxide precursors of molybdenum‐based catalysts. The presence of these additives enhances the dispersion of Keggin or Dawson heteropolyanions (HPAs) on the support by maintaining a high phosphorus‐to‐molybdenum ratio in solution. This is achieved by two strategies: triethylene glycol (TEG) exhibits a pronounced affinity for alumina hydroxyls, while citric acid compensates for phosphate adsorption through the formation of a stable Mo‐citrate complex.

Effect of metal cation coaddition in phosphovanadomolybdate anion catholytes on the redox flow polymer electrolyte fuel cell performance

Redox flow polymer electrolyte fuel cells (RFFCs) employing heteropolyanions (HPAs) as cathode redox mediators enable continuous power generation through the electrochemical reduction of the HPAs at the carbon cathode and subsequent reoxidation of the reduced-form HPAs in the cathode tank. Currently, effective reoxidation methods are required to achieve both high performance and long-term stability. Heteropolyanions such as α–[PW12O40]3– and α–[SiVW11O40]5– have increased reoxidation rates in the presence of radical species. In this study, fuel cell performance is investigated by adding Fe3+ and Cu2+ to the aqueous solution of [PV3Mo9O40]6–, which is used as a catholyte in RFFCs to increase the concentration of radicals in the system. Current–voltage measurements show that the added metal cations in the catholyte increase the power density. A temporary improvement in cell performance is observed during a prolonged current passage test.

SYNTHESIS OF SODIUM HETEROPOLY DECATUNGSTOEUROPATE(III) WITH PLATE-LIKE SURFACE MICROMORPHOLOGY

In order to develop an express procedure for the synthesis of the Eu(III)-containing heteropoly compound Na9[Eu(W5O18)2]·35H2O, a study of the interaction in an aqueous solution of the Na2WO4 – HNO3 – Eu(NO3)3 – H2O system acidified to an acidity of Z = ν(H+)/ν(WO42–) = 0.80 was carried. A procedure for obtaining a single-phase sample of Na9[Eu(W5O18)2]·35H2O is proposed, which is performed by a simple technique in a short time, which does not exceed 5 days from the addition of reactants to obtaining the target product with a yield of more than 90%. It was established that during salting out, the addition of an organic solvent (propan-2-one) results in the crystallization of Na9[Eu(W5O18)2]·35H2O normal salt with plate-like surface micromorphology. The set of oscillations characteristic for the heteropoly tungstate anion with the Peacock–Weakley type of structure, [Eu(W5O18)2]9–, was established by the methods of FT-IR spectroscopy and FT-Raman spectroscopy. By the method of FT-IR spectroscopy the absence of organic solvent molecules (propan-2-one) in the composition of the crystalline product was established. The revealed set of vibrations in the FT-IR and Raman spectra of the isolated salt (the most intense valence vibrations at 710, 797, 849, and 935 cm-1 in the FT-IR spectrum; intense bands in the region of 930–980 cm-1 in the Raman spectrum) is characteristic of the site group of the heteropoly anion [Ln(W5O18)2]9– (Ln = La–Lu) and is identical to the FT-IR and Raman spectra of salts, the crystal structure of which has been reliably established by single crystal X-ray diffraction analysis. By the method of scanning electron microscopy, it was shown that the grain size of Na9[Eu(W5O18)2]·35H2O powder is up to 500 nm. The single phase of the salt was confirmed by the uniform surface contrast in the backscattered electron imaging (BEI) mode and by the uniform distribution of Eu, Na, W, and O during the scanning of the surface in the characteristic X-ray radiation.

Adaptability of Heteropolytungstate Anions as Efficient Anode Redox Mediators in Redox Flow Polymer Electrolyte Fuel Cells.

Heteropolyanions (HPAs) are known as the candidate for an anode redox mediator for redox flow polymer electrolyte fuel cells (PEFCs). The electrochemical properties of HPAs differ depending on the transition elements and heteroatoms in HPAs. For example, heteropolytungstate anions (W-HPAs), in which the transition element is tungsten, have a lower one-electron reduction potential than other HPAs. Therefore, it has been reported that redox flow PEFCs adapted with W-HPAs exhibit high power generation performance. On the other hand, studies on the heteroatoms of HPAs are limited only to electrochemical properties, and statistical and comprehensive studies on the power generation performance of redox flow PEFCs are lacking. Thus, it is beneficial to clarify the optimal heteroatom in order to design anolytes suitable for redox flow PEFCs. In this study, heteropolytungstate anions with different heteroatoms were adapted as anodic redox mediators in a redox flow PEFC. In power generation tests, the redox flow PEFC with an anolyte of zinctungstate anion showed the highest performance. Zinctungstate anion exhibited the fastest reduction and oxidation rates among the W-HPAs investigated in this study.

Heteroelements in polyoxometalates: a study on the influence of different group 15 elements on polyoxometalate formation.

In the field of polyoxometalate (POM) chemistry, different heteroelements are integrated into the cage-like structures, to obtain different structural types of so-called heteropolyanions (HPAs). While it is generally accepted, that some elements favor certain types of structure, a systematic study is still missing. In this article, we present a systematic investigation of the influence of the group 15 elements nitrogen, phosphorous, arsenic, and antimony on the formation of different POM structure types. Our study is comprised of DFT calculations and corresponding experimental structural analysis. In this context, the DFT study establishes the thermodynamics of formation of different coordination geometries with various heteroelements on two POM structure types, the Keggin and the Anderson-Evans structures. Our POM synthesis experiments were performed at two different pH values (1 and 5) and resulted in a variety of heteropolytungstates, which were identified and characterized by elemental analysis as well as single crystal X-ray diffraction and vibrational spectroscopy. With these methods, we were able to establish a clear trend, showing that heavier elements lead to formation of different structure types than lighter elements. These results signify a large step towards a better understanding of POM formation specifically with respect to the choice of heteroelement.

Development of electrocatalytic hybrid film based on conducting polypyrrole–heteropolyanion

The investigation focused on integrating heteropolyanions (HPAs) into a polymeric matrix of polypyrrole (PPy), aiming to achieve effective immobilisation for potential electrocatalytic applications. Specifically, the successful immobilization of a Dawson-type mixed addenda HPA, α2 – K8[P2W17V4+O62].10H2O, within conductive PPy films was achieved. These [P2W17V4+O62]-doped PPy films exhibited robust stability at both pH 2 and pH 7 during continuous potential cycling involving the V5+/4+ redox process. However, it was noted that in the negative potential range leading to polymer backbone reduction, the HPA tended to leach out from the film. In terms of catalytic assessments, the [P2W17V4+O62]-dopped PPy films displayed noteworthy electrocatalytic performance in the oxidation of ascorbic acid. Notably, they demonstrated a sensitivity of 8.18 (+/-0.15) μA mM−1 and a limit of detection (LOD) of 1.65 mM at pH 2.0. Furthermore, under neutral conditions, the films exhibited a sensitivity of 6.97 (+/-0.30) μA mM−1 and a LOD of 4.24 mM. Further, endeavours were made to immobilise alternative variations of HPAs, specifically, the crown HPA, K28Li5H7P8W48O184·92H2O, and Cu2+ substituted Krebs HPA, KxNa(10-x)Bi2W20Cu2O70(H2O)6·30H2O (with × ranging from 1 to 10), into PPy films. Initial findings from these attempts are also briefly discussed in this study.

Lacunary silicotungstic heteropoly salts as high-performance catalysts in oxidation of cyclopentene

• Development of lacunary Keggin heteropoly anions by one-pot simplified process. • Functionalized ionic liquid-based catalysts for efficient oxidation of cyclopentene. • The di-lacunary heteropoly anions shows higher intramolecular oxidative capacity and stability. • In situ FT-IR reveals the reaction trend of intermediates and active species. The development of polyoxometalates for olefin oxidation is critical to achieving the green chemical process of the C5 fraction further processing. Di-lacunary silicotungstic anions were easily obtained by continuously adjusting the pH instead of the traditional step-by-step method, which exhibited excellent performance in the catalytic oxidation of cyclopentene to aldehydes or alcohols. The 93.69% CPE conversion and 97.15% total product selectivity (41.38% for GA and 55.77% for 1,2-diol) were achieved by using H 2 O 2 as the oxidant and acetonitrile as the solvent. Through complementary characterization, it was found that the optimized di-lacunary silicotungstic polyoxometalate retained a complete Keggin structure, and exhibited better catalytic activity and stability than the mono-lacunary or saturated silicodecatungstate because it exposed more catalytic active centers. Furthermore, in situ FT-IR spectra was utilized to monitor the reaction process, revealing the formation of the active species W(O 2 ) on the di-lacunary silicotungstic polyoxometalate and the intermediate epoxycyclopentane during the catalytic oxidation of cyclopentene.

Hydrolysis-oxidation of cellulose to formic acid in the presence of micellar vanadium-containing molybdophosphoric heteropoly acids

OxFA-processing of inedible cellulose is considered as a perspective way for the production of biogenic formic acid (FA) which appeared to be a promising source for sustainable energy. In our work, the one-pot hydrolysis-oxidation of cellulose to FA was studied in the presence of the micellar acidic catalysts based on Mo–V–P heteropoly acids [Cn-MIM]y/H3+x-yPMo12-xVx (n = 6, 10 and 16; x = 1, 2 and 4; y = 2–6). The influence of amount of V, substitution of H+ by [Cn-MIM] and the length of alkyl group Cn of the cation was revealed. The optimization of the reaction conditions was also performed. To our knowledge, heterogeneous catalysts of such a composition were applied in cellulose hydrolysis-oxidation to FA for the first time. In the presence of C10-MIM/HPMo11V catalyst, the optimal reaction conditions were determined: 10 g/L of cellulose, 1.25–10 g/L of catalyst, 5 MPa of gas mixture (O2/N2 - 20/80 vol/vol) and 170–180 °C. Decreasing the alkyl group length of Cn-MIM+ cation or V content into framework of heteropoly anion were revealed to rise up the yield of the target product. These correlations were caused by the following factors. First, the decreasing acidity of micellar catalysts. Senond, the change in distribution of electron density in heteropoly anion due to the interaction between hydrogen atoms of alkyl group of Cn-MIM cation and oxygen atom of heteropoly anion. Third, blocking of V active sites for reagents. Influence of acidity on catalytic properties of micellar catalysts was also revealed in the course of screening samples with the different degree of protons substitution by C16-MIM+. The reaction rate was demonstrated to rise with increasing degree of protons substitution by C16-MIM + cation in C16-MIM/HyPMo11V and C16-MIM/HyPMo8V4 samples. The yield of FA up to 45 mol% can be reached over micellar HPA catalysts studied.

The Effect of Nanosized Silicon Molybdate Anions on the Plasma Membrane of Human Fetal Fibroblasts

We used time-of-flight secondary ion mass spectrometry (ToF-SIMS) to study changes in the composition of the plasma membranes of human fetal fibroblasts under the action of nanosized anions of silicon molybdic acid. The dependences of the mass spectra of the main lipids of the plasma membranes on the silicon molybdate concentration were measured and interpreted; the dependences correlate with the layer-by-layer distributions and with the affinity of cholesterol for phospholipids. A new effect for cell biochemistry was discovered, that is, a significant decrease in the relative concentrations of cholesterol and sphingomyelin in plasma membranes under the effect of multiply charged heteropoly anions (HPAs). In aqueous silicon molybdate solutions with a concentration of c ≈ 10 µM/L and an exposure time of 48 h, the amount of cholesterol in plasma membranes decreased by 2–2.5 times, while the amount of sphingomyelin decreased by 20–25%. A new mechanism is proposed for the initial effect of HPA on plasma membranes, which consists of selective etching by multiply charged anions. According to the proposed mechanism, cholesterol and sphingomyelin, the main regulators of permeability and microviscosity of plasma membranes, are extracted from the plasma membrane at the first stage of the interaction of the polyoxometallate anion with the cell. As a consequence of the increased permeability of the plasma membranes in cells, acceleration of vital transmembrane and lateral processes may occur.

Investigation of Acid Characteristics of Oxo Complex Catalysts of Isomerization of Pentane—Hexane Fractions

A new catalyst, based on newly synthesized inorganic superacids, was developed for the isomerization of light hydrocarbons. A series of mixed heteropoly anions with a modified Keggin structure containing different transition metals (including platinum group metals) were synthesized for this purpose. The technology for the production of superacidic catalysts with a coating of modified heteropoly complexes of the Keggin series on different supports was developed. The Bronsted and Lewis acid sites of the developed superacidic oxo complex catalyst deposited on various supports were investigated.

PH‐Dependent Interactions between Keggin Heteropolyanions in Dilute Solutions

Keggin phosphotungstate heteropolyanions (HPA), PW12O403–, are known to interact via short‐range attraction and long‐range repulsion (SALR) at moderate and high solution concentrations and low‐pH (pH = 1). These interactions were identified through the observation of structure factor peaks in small‐angle X‐ray scattering (SAXS) data reported previously (J. Phys. Chem. C 2016, 120, 1317). Here we describe the interactions between the same heteropolyanions with extremely low concentrations at low (pH = 0) and high pH (pH = 4.7) conditions. The solution chemistry of Keggin heteropolyanions at these two pH values provides a unique way to change the charge of the cluster anions without changing the structure (from the perspective of SAXS) and, at the same time, changing the hydrogen bonding interactions. The structure factors obtained from concentration dependent SAXS data reveal that the change in pH changes the nature of SALR interactions, consistent with the presence of the plenary PW12O403− anion at pH = 0 and the monovacant lacunary PW11O397– anion at pH = 4.7. At the low pH condition, the attractive interactions dominate to provide a peak near Q = 0 Å−1 momentum transfer in the structure factors, whereas at pH = 4.7 the repulsive interactions dominate, thereby eliminating the peak near Q = 0 Å−1. The experimental results presented here are in agreement with the recent liquid state theory and computer simulation predictions on SALR interactions.

A polyoxometalate gel electrolyte with enhanced electrochemical performance

A novel hybrid gel electrolyte has been synthesized by self-assembling of 1-(3-sulfonic group) propyl pyridine (PyPS) cation and the heteropoly anion. The results of FTIR spectra and XRD patterns indicate the synthesized hybrid gel electrolyte [PyPS]5SiMo[Formula: see text]VO[Formula: see text] possesses lamellar structure with [Formula: see text]-spacing of 2.09[Formula: see text]nm. The electrochemical stability potential window is up to 3[Formula: see text]V. Ionic conductivity of [Formula: see text][Formula: see text]S[Formula: see text]cm[Formula: see text] was observed above the phase transformation temperature under ambient condition. The conductivity enhances with increasing temperatures.

An Atom‐Economical Route to Substituted β‐Arylethyl Ketones: Phosphomolybdic Acid‐Catalyzed Carbohydroxylation of Terminal Alkynes in Organic Carbonate

AbstractA highly efficient and atom‐economical route for the synthesis of substituted β‐arylethyl ketones was developed by using cheap phosphomolybdic acid (H3PMo12O40) as catalyst and non‐volatile propylene carbonate (PC) as green solvent via the carbohydroxylation of terminal alkynes with benzylic alcohols under mild conditions. Various functional groups on the benzylic alcohols and terminal alkynes were tolerated, giving the corresponding substituted β‐arylethyl ketones as products in good to excellent yields (up to 95%). It is worth noting that a turnover number (TON) of up to 520 was achieved in the protocol. The mechanism investigation showed that PC might stabilize the heteropoly anion and the carbocation intermediate thus facilitating the carbohydroxylation reaction.magnified image

Screening of Novel Materials for Biodiesel Production Through the Esterification of Oleic Acid

The present contribution screens the specific activity of various inorganic and enzymatic based materials in the esterification of oleic acid that is typically used as a test reaction for the production of biodiesel from high free fatty acid feedstocks. The inorganic materials investigated in this contribution are bulk fosfotungstic heteropoly acid of the Wells Dawson structure H6P2W18O62.nH2O (HPA), as well as dispersed on titanium dioxide 18 % w/w H6P2W18O62/TiO2 and the insoluble cesium salt of the Wells Dawson heteropoly anion Cs2H4P2W18O62. Additionally, the commercial biocatalyst Novozym® 435 (immobilized lipase B of Candida antarctica) and a self-supported lipase of vegetable origin obtained from the latex Araujia sericifera (ASL) were studied among the materials of enzymatic nature. The density and accessibility of Bronsted acid sites have a key role in the specific activity of the fosfotungstic based heteropoly compounds. The HPA dispersed over an oxide support catalyzed the esterification of the fatty acid in a heterogeneous fashion with the highest activity (6.4 µmol mg−1 h−1 at 85 °C) among the inorganic materials. In contrast, the enzymatic materials are more active at lower temperature than the inorganic ones. Particularly, ASL catalyzed the homogenous methanolysis with the highest specific activity (30.7 µmol mg−1 h−1 at 40 °C) at the lowest temperature among the materials assayed.

Synthesis and structure of dodecamolybdates of tetravalent cerium, thorium, uranium, neptunium, and plutonium

A series of isostructural compounds of the composition Na7H[EMo12O42]·12H2O, where E(IV) = Ce, Th, U, Np, or Pu, were synthesized and structurally characterized. In the [EMo12O42]8– heteropolyanion (HPA), the central E(IV) atom is surrounded by six Mo2O9 groups, each constituted by two octahedra sharing a common face. The coordination polyhedron (CP) of the central atom is a weakly distorted icosahedron with the mean E(IV)–О bond lengths of 2.498, 2.529, 2.500, 2.490, and 2.488 A for Ce, Th, U, Np, and Pu, respectively. In the structure of the compounds Na7H[EMo12O42]·12H2O, there are two crystallographically independent sodium atoms: Na(1) and Na(2). The oxygen surrounding of the Na(1) atom is formed by the terminal oxygen atoms of two heteropolyanions adjacent along [001], and its coordination polyhedron is an octahedron. The surrounding of the Na(2) atom (a six-vertex polyhedron) is formed by three terminal oxygen atoms of three Mo2O9 groups belonging to the same HPA and by three water molecules. The coordination polyhedra of the Na(2) atoms are linked with each other via common oxygen atoms of Ow(2) water molecules to form a chain “winding” around the 31 screw axis. The heteropolyanions and Na+ cations in the crystal form a framework constructed in a fashion characteristic of Dexter–Silverton type anions, with the coordination via three terminal oxygen atoms of three Mo2O9 groups. Excess negative charge of HPA is compensated by the proton localized on one of the six bridging O atoms. In the Mo2O9 doubled octahedra, the Mo–O bonds with the О atoms bonded to E(IV) and forming the edge of the common face are sensitive to the kind of the central atom.

CoMo sulfur-tolerant water-gas shift catalyst derived from an Anderson-type heteropolyanion precursor

The use of heteropolyanions (HPAs) as starting materials can be an interesting strategy for preparing highly active bimetallic catalysts. In this paper, an Anderson-type Co2Mo10-HPA was synthesized by precipitation method, and was further used as starting precursor to prepare a Co2Mo10/Al2O3 sulfur-tolerant water-gas shift (WGS) catalyst. It is shown that the close proximity of cobalt and molybdenum atoms in Co2Mo10-HPA precursor leads to a strong interaction between Co and Mo species and an easy second-step reduction of Mo oxides on the obtained catalyst, and thus remarkably improves the catalytic activity in sulfur-containing WGS reaction.

Aggregation of Heteropolyanions Implicates the Presence of Zundel Ions Near Air‐Water Interfaces

AbstractProtons play crucial roles in the interactions between heteropolyanions (HPAs) in aqueous solutions and solid acid salts. We report the aggregation behaviours of Keggin HPAs near the surfaces of heteropolyacid solutions. The structure of the aggregated HPA layer near the solution–vapour phase boundary closely resembles the solid‐state crystal structure of the heteropolyacids in which the HPAs are connected by Zundel ions. The resemblance not only implicates the presence of protons in the form of planar Zundel ions near the air‐water interface but, also, suggests that these align parallel to the interface. This study demonstrates an indirect means of assessing the impact of protons on HPA interactions near air‐water interfaces and, in general, provides new insights about interfacial proton chemistry of heteropolyacids.

Fe4(SiW12O40)3-catalyzed glycerol acetylation: Synthesis of bioadditives by using highly active Lewis acid catalyst

In order to investigate the effect of Lewis acidic metals on the acid properties of Keggin heteropolyacids catalysts, a set of metal-exchanged HPAs (i.e. M3/nPW12O40, M3/nPMo12O40 and M4/nSiW12O40 (M=Cu, Co and Mn, n=2; M=Fe, n=3) were synthesized and their activity on glycerol esterification with acetic acid was evaluated. This procedure avoids the use of corrosive Brønsted acid catalysts. Regardless of the heteropoly anion, the activity of catalysts in terms of metal cations followed the sequence: Fe3+>Cu2+>Mn2+>Co2+. It has been found that among the HPAs, only H4SiW12O40 has the acidic protons that can be successfully exchanged with Fe3+ cations, resulting in Fe4(SiW12O40)3 salt, the most active and selective catalyst. The highest conversion (ca.99.9%) was achieved in Fe4(SiW12O40)3-catalyzed esterification reactions, along with the highest selectivity for di and triacetyl glycerol (ca.55 and 42%, respectively). Effects of temperature, stoichiometry of reactants, concentration and nature of catalysts were assessed. A kinetic study of Fe4(SiW12O40)3 or H4SiW12O40-catalyzed reactions was conducted and the activation energy determined.

Hydroprocessing catalysts based on transition metal sulfides prepared from Anderson and dimeric Co2Mo10-heteropolyanions. A review

Hydroprocessing catalysts based on transition metal sulfides have been extensively used worldwide in refineries for upgrading heavy fractions to better quality fuels. The present work reviews the studies dealing with Anderson heteropolyanions (HPAs) and the derived dimeric structure for synthesizing hydrotreating catalysts. The development of new preparation methods based on HPA catalysts led to efficient catalytic systems due to better sulfidation allowed by a better dispersion of the oxidic precursor even at high metallic loadings. The increase of the Co/Mo ratio in the heteropolycompounds up to 0.5 was possible due to the formation of dimer cobalt salt. The association of Co and Mo at the molecular level in the same heteropolycompound preserved after the drying step during the catalyst preparation ensured the efficiency of the promoting effect with a higher quantity of the CoMoS active phase. This HPA-based system was further improved by the simultaneous use of HPAs and chelating agents. Les catalyseurs d’hydrotraitement à base de sulfures de métaux de transition sont utilisés en raffineries pour convertir les coupes pétrolières en carburants. Ce travail est une revue des études utilisant les hétéropolyanions de type Anderson et la structure dimérique qui en dérive pour la synthèse de catalyseurs d’hydrotraitement. Le développement de nouvelles méthodes de préparation de catalyseurs basées sur les HPA a permis l’obtention de systèmes catalytiques efficaces, pour lesquels la meilleure sulfuration est liée à une meilleure dispersion du précurseur oxyde. En particulier, l’association du Co et du Mo à l’échelle moléculaire dans le sel de cobalt du dimère d’Anderson, dont la structure est préservée après l’étape de séchage lors de la synthèse du catalyseur, explique l’efficacité de l’effet promoteur, qui se traduit par une quantité de sites CoMoS plus importante. Ce système a été amélioré par la suite par une utilisation simultanée des HPAs et d’agents chélatants.

Aggregation of Heteropolyanions in Aqueous Solutions Exhibiting Short-Range Attractions and Long-Range Repulsions

Charged colloids and proteins in aqueous solutions interact via short-range attractions and long-range repulsions (SALR) and exhibit complex structural phases. These include homogeneously dispersed monomers, percolated monomers, clusters, and percolated clusters. We report the structural architectures of simple charged systems in the form of spherical, Keggin-type heteropolyanions (HPAs) by small-angle X-ray scattering (SAXS) and molecular dynamics (MD) simulations. Structure factors obtained from the SAXS measurements show that the HPAs interact via SALR. Concentration and temperature dependences of the structure factors for HPAs with −3e (e is the charge of an electron) charge are consistent with a mixture of nonassociated monomers and associated randomly percolated monomers, whereas those for HPAs with −4e and −5e charges exhibit only nonassociated monomers in aqueous solutions. Our experiments show that the increase in magnitude of the charge of the HPAs increases their repulsive interactions and inhi...