Polyelectrolytes In Water Research Articles

Bioinspired Self-Assembly of Metalloporphyrins and Polyelectrolytes into Hierarchical Supramolecular Nanostructures for Enhanced Photocatalytic H2 Production in Water.

Polypeptides, as natural polyelectrolytes, are assembled into tailored proteins to integrate chromophores and catalytic sites for photosynthesis. Mimicking nature to create the water-soluble nanoassemblies from synthetic polyelectrolytes and photocatalytic molecular species for artificial photosynthesis is still rare. Here, we report the enhancement of the full-spectrum solar-light-driven H2 production within a supramolecular system built by the co-assembly of anionic metalloporphyrins with cationic polyelectrolytes in water. This supramolecular photocatalytic system achieves a H2 production rate of 793 and 685 μmol h-1 g-1 over 24 h with a combination of Mg or Zn porphyrin as photosensitizers and Cu porphyrin as a catalyst, which is more than 23 times higher than that of free molecular controls. With a photosensitizer to catalyst ratio of 10000 : 1, the highest H2 production rate of >51,700 μmol h-1 g-1 with a turnover number (TON) of >1,290 per molecular catalyst was achieved over 24 h irradiation. The hierarchical self-assembly not only enhances photostability through forming ordered stackings of the metalloporphyrins but also facilitates both energy and electron transfer from antenna molecules to catalysts, and therefore promotes the photocatalysis. This study provides structural and mechanistic insights into the self-assembly enhanced photostability and catalytic performance of supramolecular photocatalytic systems.

Bioinspired Self‐Assembly of Metalloporphyrins and Polyelectrolytes into Hierarchical Supramolecular Nanostructures for Enhanced Photocatalytic H2 Production in Water

AbstractPolypeptides, as natural polyelectrolytes, are assembled into tailored proteins to integrate chromophores and catalytic sites for photosynthesis. Mimicking nature to create the water‐soluble nanoassemblies from synthetic polyelectrolytes and photocatalytic molecular species for artificial photosynthesis is still rare. Here, we report the enhancement of the full‐spectrum solar‐light‐driven H2 production within a supramolecular system built by the co‐assembly of anionic metalloporphyrins with cationic polyelectrolytes in water. This supramolecular photocatalytic system achieves a H2 production rate of 793 and 685 μmol h−1 g−1 over 24 h with a combination of Mg or Zn porphyrin as photosensitizers and Cu porphyrin as a catalyst, which is more than 23 times higher than that of free molecular controls. With a photosensitizer to catalyst ratio of 10000 : 1, the highest H2 production rate of >51,700 μmol h−1 g−1 with a turnover number (TON) of >1,290 per molecular catalyst was achieved over 24 h irradiation. The hierarchical self‐assembly not only enhances photostability through forming ordered stackings of the metalloporphyrins but also facilitates both energy and electron transfer from antenna molecules to catalysts, and therefore promotes the photocatalysis. This study provides structural and mechanistic insights into the self‐assembly enhanced photostability and catalytic performance of supramolecular photocatalytic systems.

Neutral polymer-pseudo polyelectrolyte transition of a post irradiated polymer dissolved in water

The purpose of this study is to study the conformation transition of a post irradiated polymer dissolved in water. In fact, polyvinylpyrrolidone (PVP) in powder(Mw = 1.300.000 g/mol), is irradiated with various doses, D, ranged from 0.3 to 50 kGy of 60Co-gamma. The irradiated polymer, PVP*, is dissolved in water to obtain post irradiated solutions of different concentration. After the stabilization of the obtained solutions (48 h), refractometry and viscosity measurements, are used to characterize the post irradiated aqueous solutions at 25 °C. The specific volume of PVP* dissolved in water was determined according modified Lorentz-Lorenz and Gaston-Dale equations, showing two dependence on the dose, D. For D ≤ Dc = 20 kGy, the specific volume increases and for D ≥ Dc, the specific volume decreases. The reduced viscosity of PVP*(Mw = 1.300.000 g/mol) aqueous solution permits to delimit the dilute and semi dilute regimes concentration and deduce the overlapping concentration, C*PVP*(D), which found to be insensitive to the dose value. For D < Dc, the intrinsic viscosity PVP* dissolved in water is determined according a modified Huggins equation and so the irradiated polymer behaves as neutral polymer. However, when D = DC the intrinsic viscosity values calculated according modified Fuoss and Fedors equations are very close and the irradiated polymer behaves as a polyelectrolyte in water. For D > Dc, the modified Fedors equation describes perfectly the evolution of the reduced viscosity versus irradiated polymer concentration. So, PVP* behaves as a polyelectrolyte in water and a neutral polymer – pseudo polyelectrolyte transition occurs under gamma irradiation effect. The irradiated polymer molar mass, MwPVP∗(D), was determined by comparing its intrinsic viscosity to these established according the Mark Howink Shakurada equation. MwPVP∗(D) decreases by increasing the dose value, which confirm the scission the polymer chain under gamma irradiation effect.

Engineering the Coacervate Microdroplet Interface via Polyelectrolyte and Surfactant Complexation.

Complex coacervate microdroplets, which are formed via spontaneous liquid-liquid phase separation by mixing two oppositely charged polyelectrolytes in water, have emerged as a new paradigm in the fields of origin of life, membraneless subcellular compartmentalization, bioreactors, and drug delivery. However, how to further improve its stability and enhance its selectivity in one particular coacervate system remains a challenge. By generating a membrane-like layer at the surface of coacervate microdroplets via electrostatic interactions between oppositely charged surfactants and polyelectrolytes, we here achieve tunable permeability and enhanced stability of the coacervates at the same time. Depending on the surfactants used, membrane-like layer-coated coacervate microdroplets exhibit different selectivity over solute sequestration and can promote or inhibit DNA hybridization. Our approach provides a practical tool to engineer functional bioinspired microcompartments with potential applications in the fields of controlled drug release and microreactor technology.

On The Use of Polyelectrolytes in Water and Wastewater Treatment.(Dept.P)

On The Use of Polyelectrolytes in Water and Wastewater Treatment.(Dept.P)

Hydrogen-bonded network enables polyelectrolyte complex hydrogels with high stretchability, excellent fatigue resistance and self-healability for human motion detection

Polyelectrolyte complex hydrogel (PECH) is an emerging ion conductive hydrogel made from non-covalent interacted oppositely charged polyelectrolytes in water. However, the construction of PECH with high stretchability, excellent fatigue resistance and self-healability is heavily demanded while remaining a profound challenge. Herein, a hydrogen-bonded network densification strategy is presented for preparing a highly stretchable and deformation-tolerant PECH hydrogel (Fe/CS/PAA), which is composed of an anionic Fe3+-coordinated polyacrylic acid network (Fe-PAA) and cationic Fe3+-coordinated chitosan network (Fe-CS). Benefiting from the formation of dense hydrogen-bonded network between the Fe-PAA and Fe-CS networks activated by salt impregnation, the resultant densified hydrogen-bonded Fe/CS/PAA hydrogel (DHB-Fe/CS/PAA) exhibits large tensile strength (~0.34 MPa), high stretchability (~1370%), low-temperature resistance to −25 °C, and heat-accelerated self-healability. Due to its high stretchability, excellent fatigue resistance and high ionic conductivity, the DHB-Fe/CS/PAA can readily work as a stretchable ionic conductor for skin-inspired ionic strain sensor, displaying high sensitivity in a wide strain range (0.5%–500%), fast response time (<180 ms) and excellent durability for 500 cycles at a 100% strain. Besides, the as-assembled ionic sensor is capable of maintaining high ionic conductivity and mechanical robustness at a sub-zero temperature of −25 °C ascribing to the presence of high-concentration charged functional groups and impregnated salts. As a demonstration, a wearable DHB-Fe/CS/PAA ionic sensor in a resistive mode is assembled, demonstrating high sensitivity, wide response range and excellent cyclability in detecting and distinguishing complex human motions rapidly and in real-time.

Studies of aggregation properties of surfactant with and without polyelectrolyte in water and binary mixture of methanol-water from the surface tension measurements

The critical aggregation concentration (cac), polymer saturation concentration (psc), critical micellar concentration (cmc) and the apparent critical micellar concentration (cmc*) of cetyltrimethylammonium bromide (CTAB) and sodium polystyrene sulfonate (NaPSS) system are studied from the surface tension method. The standard free energy of micellization (∆Gmο), maximum surface excess concentration (Γmax), area occupied by per surfactant molecule (Amin), surface pressure (πcmc), solution surface tension (γcmc), solvent surface tension (γo), the effect of NaPSS concentration and CTAB/NaPSS molar ratio, slope (dγdlogC), correlation of ∆Gmο with Gordon parameter (G), correlation of γoγcmc with the binary mixture of methanol-water, free energies of adsorption (Gadsο), the efficiency of adsorption (pC20), Gibbs energy difference (∆Gpsο), degree of binding (β), packing parameter (P), effective Gibbs free energy (∆Geffο), aggregation number (N), the relation between Amin and πcmc, correlation of ΓΓmax, cmcC20, ΔGadsοΔGmο, cmcpC20, C20 and Gmin with the binary mixture of methanol-water are also discussed.

Solvation Behaviors of Poly(acrylic acid) in Mixed Solvents of 2-Butoxyethanol + Water

Poly(acrylic acid) (PAA) is a well known weak polyelectrolyte in water but little is known about the solvation behavior of PAA in the mixtures of alcohol + water. In this study, the solvation behavior of PAA in the mixed solvents composed of 2-butoxyethanol (2BE) + water were investigated by measurements of volumetric properties, electrical conductivity, resonance light scattering and dynamic light scattering. All the measured experimental properties showed extrema or abrupt changes at a 2BE mole fraction of about 0.017 in 2BE + water. This may be explained by the formation of aggregates of 2BE and water, which is a poor solvent for PAA and results in cononsolvency of PAA in the mixture of the two good solvents, 2BE and water. We found that the volumetric property is sensitive to the occurrence of the specific aggregate of 2BE and water and the interactions in the complex fluid mixtures.

Polyelectrolyte complex coacervation by electrostatic dipolar interactions.

We address complex coacervation, the liquid-liquid phase separation of a solution of oppositely charged polyelectrolyte chains into a polyelectrolyte rich complex coacervate phase and a dilute aqueous phase, based on the general premise of spontaneous formation of polycation-polyanion complexes even in the homogeneous phase. The complexes are treated as flexible chains made of dipolar segments and uniformly charged segments. Using a mean field theory that accounts for the entropy of all dissociated ions in the system, electrostatic interactions among dipolar and charged segments of complexes and uncomplexed polyelectrolytes, and polymer-solvent hydrophobicity, we have computed coacervate phase diagrams in terms of polyelectrolyte composition, added salt concentration, and temperature. For moderately hydrophobic polyelectrolytes in water at room temperature, neither hydrophobicity nor electrostatics alone is strong enough to cause phase separation, but their combined effect results in phase separation, arising from the enhancement of effective hydrophobicity by dipolar attractions. The computed phase diagrams capture key experimental observations including the suppression of complex coacervation due to increases in salt concentration, temperature, and polycation-polyanion composition asymmetry, and its promotion by increasing the chain length, and the preferential partitioning of salt into the polyelectrolyte dilute phase. We also provide new predictions such as the emergence of loops of instability with two critical points.

Synthesis of Clay Composites of Polyacrylamide and Poly-2-Hydroxyethylacrylate and Sorbtion Ability in the Case of Cetylpyridinium Bromide

&lt;p&gt;By the three-dimensional polymerization of nonionic (polyhydroxyethylacrylate and polyacrylamide) &lt;br /&gt;polymers and bentonite clay from Manyrak deposit (East Kazakhstan Region) and with using of process &lt;br /&gt;preliminary intercalation of monomers in an aqueous suspension of bentonite (polymerization in situ) the &lt;br /&gt;chemically crosslinked composite gels were synthesized. Optimal conditions of synthesis and physical-chemical properties of composition gels were established. It was shown, that yield of gel fraction increases &lt;br /&gt;with increasing contents of bentonite clay. Insignificant adding of negative charged particles of bentonite clay &lt;br /&gt;gives to polymer gels of nonionic type polyelectrolyte character, that comes out in decreasing of swelling &lt;br /&gt;degree of gels under effect of ionic strength. By using physical and chemical methods of research: equilibrium &lt;br /&gt;swelling, IR spectroscopy, scanning electron microscope (SEM), sorption-desorption, etc. were shown the &lt;br /&gt;formation of compatible, homogeneous, swelling in water polyelectrolyte gels formed via hydrogen bonds &lt;br /&gt;between the components of the gel, stabilized by hydrophobic interactions of the organic polymer chains. &lt;br /&gt;The possibility of the regulation of swelling ability of the composite gels through varying of the outside and &lt;br /&gt;inside factors as: consist of the composition, conditions of intercalation, pH of the environment, temperature &lt;br /&gt;and ionic strength was established, that is stimulus sensitivity of gels. The sorbtion capacity of polymer-clay composites in attitude surface active substance cetylpyridinium bromide were estimated. Increasing of &lt;br /&gt;temperature of environment and content of bentonite clay in composite promotes the process of sorbtion &lt;br /&gt;of surface-active substances. Considerably high sorption capacity of polymer clay composition based on &lt;br /&gt;more hydrophilic polymer – polyacrylamide was established. By the results of investigations one may, that &lt;br /&gt;synthesized polymer clay composites after suitable investigations can be recommend as sorbents of cationic &lt;br /&gt;surface active substances.&lt;/p&gt;

Preconcentration and spectrophotometric determination of polyDADMAC in treated water by in situ co-precipitation with naphthalene

Polydiallyldimethylammonium chloride (polyDADMAC) is a water-soluble cationic polyelectrolyte used as a flocculant in water treatment works. Unreacted traces in water react with chlorine to produce a carcinogenic compound during the disinfectation process. This study reports on a preconcentration procedure and spectrophotometric determination of polyDADMAC at trace levels in treated water by in situ co-precipitation with naphthalene with a view to come up with an analytical tool that will be used by water works to routinely monitor the polycation in an effort to supply safe water to consumers. Preconcentration of polyDADMAC polyelectrolyte in water at trace levels was achieved by co-precipitating the polyelectrolyte with naphthalene. This resulted in the formation of a water insoluble adsorbent with a high affinity for azo dyes. The formation of this material was based on multilayer assembly of organic polyelectrolyte systems resulting to multilayers through a layer-by-layer self-assembly process. The co-precipitate was formed by mixing aqueous solutions containing varying concentrations of polyDADMAC with different volumes of solutions containing 0.75g of naphthalene dissolved in acetone. The resulting respective precipitates were packed in different glass columns and a solution of the dye was eluted through each column. The contents of each column were then dissolved in 10mL of dimethylformamide (DMF) and the absorbance readings of the resulting solutions recorded. The wavelength of maximum absorption was found to be 540nm at pH 12.0. A linear calibration for polyDADMAC solutions was obtained with a correlation coefficient of 0.976. The detection limit was found to be 1.90×10−4μgmL−1 and the method was applied to determine the concentration of polyDADMAC residue in treated water.

Study of the structure dependent behavior of polyelectrolyte in water

We examine the effect of pendant architecture on linear polyelectrolytes in solution using molecular dynamics simulations. A comparison is done between the standard bead-spring polyelectrolyte system and a system which has the charged beads pendant to neutral backbone beads. Recent simulations of ionomer melts have found significant differences in the structure between the two architectures, but we find the structure is not dramatically affected by the different geometry. In general, the backbone architecture is slightly more compact than the pendant architecture. The counterion condensation is typically larger for the backbone systems, which yields the more compact structures. Only when both the Bjerrum length is much larger than the spacing between charges and the spacing between pendants is twice the backbone bead spacing, is the peak in the monomer-counterion radial distribution function larger for the pendant architecture. The radius of gyration for the pendant remains larger than backbone architecture because of the extra excluded volume of the pendant.

Highly Disordered Carbon as a Superior Anode Material for Room‐Temperature Sodium‐Ion Batteries

Highly Disordered Carbon as a Superior Anode Material for Room‐Temperature Sodium‐Ion Batteries

High-throughput cellular screening of engineered ECM based on combinatorial polyelectrolyte multilayer films

The capacity to engineer the extracellular matrix is critical to better understand cell function and to design optimal cellular environments to support tissue engineering, transplantation and repair. Stacks of adsorbed polymers can be engineered as soft wet three dimensional matrices, with properties tailored to support cell survival and growth. Here, we have developed a combinatorial method to generate coatings that self assemble from solutions of polyelectrolytes in water, layer by layer, to produce a polyelectrolyte multilayer (PEM) coating that has enabled high-throughput screening for cellular biocompatibility. Two dimensional combinatorial PEMs were used to rapidly identify assembly conditions that promote optimal cell survival and viability. Conditions were first piloted using a cell line, human embryonic kidney 293 cells (HEK 293), and subsequently tested using primary cultures of embryonic rat spinal commissural neurons. Cell viability was correlated with surface energy (wettability), modulus (matrix stiffness), and surface charge of the coatings.Our findings indicate that the modulus is a crucial determinant of the capacity of a surface to inhibit or support cell survival.

A Simple and Effective Approach to Vesicles and Large Compound Vesicles via Complexation of Amphiphilic Block Copolymer With Polyelectrolyte in Water

This work reports for the first time a simple and effective approach to trigger a spheres-to- vesicles morphological transition from amphiphilic block copolymer/polyelectrolyte complexes in aqueous solution. Vesicles and large compound vesicles (LCVs) were prepared via complexation of polystyrene-block-poly(ethylene oxide) (PS-b-PEO) with poly(acrylic acid) (PAA) in water and directly visualized using cryo-TEM. The complexation and morphological transitions were driven by the hydrogen bonding between the complementary binding sites on the PAA and PEO blocks of the block copolymer. The findings in this work suggest that complexation between amphiphilic block copolymer and polyelectrolyte is a viable approach to vesicles and LCVs in aqueous media.

Does cation dehydration drive the binding of metal ions to polyelectrolytes in water? What we can learn from the behaviour of aluminium(iii) and chromium(iii)

Much stronger binding is seen in aqueous solutions between the anionic polyelectrolyte potassium poly(vinyl sulfate) and the substitution labile aluminium(III) than with the kinetically inert chromium(III). This strongly supports the idea that entropy driven water loss from the hydration sphere of the metal ion plays a major role in driving binding of the trivalent metal ion to the polyelectrolyte.

Novel inorganic-organic composite coagulants based on aluminium

In this study, the preparation of a novel coagulant is examined, by introducing into PACl a cationic polyelectrolyte (CPE). For this purpose, poly-diallyldimethylammonium chloride (p-DADMAC) was used, a commonly applied cationic polyelectrolyte in water and wastewater treatment. Several possible derivatives of the composite coagulant were prepared, based on different CPE content (Al/CPE ratio, w/w). The products were characterized by means of polymerization degree (aluminium species distribution), chemical bonding (FT-IR spectroscopy), conductivity, turbidity and pH, in order to examine the impact of CPE addition in the properties of PACl. Moreover, their coagulation performance was evaluated for the treatment of contaminated tap water and compared to the respective performance of the combined application of PACl and CPE but as separated reagents. Finally, the kinetics of coagulation-flocculation was studied by aims of a Photometric Dispersion Analyzer (PDA). From the results obtained it was revealed that despite the deterioration of the charge neutralization capability when the two reagents are combined into one, the composite coagulants are more efficient in water treatment due to more effective particles aggregation. The most important advantages of the new coagulants are the significant reduction of CPE dosage (or content) and the lower residual aluminium concentration. Specific attention has to be given to the CPE content, in order to produce an improved coagulant which can achieve efficient charge neutralization combined with enhanced particles aggregation, leading to more efficient and cost-effective treatment.

A model for the Gibbs energy of aqueous solutions of polyelectrolytes

A new model for the excess Gibbs energy of aqueous solutions of polyelectrolytes is presented and applied for the correlation of the activity of water in aqueous solutions of polyelectrolytes without as well as with an added (single) salt. The model considers the phenomenon of counterion condensation, i.e., the partial dissociation of highly charged polyelectrolytes in water. Three parameters (a binary interaction parameter between polymer segments, the equilibrium constant of the dissociation reaction and a parameter which accounts for the polymer configuration) were fitted to the experimental results. The model allows for a reliable correlation of experimental results for the osmotic coefficient of aqueous solutions of a single polyelectrolyte (without as well as with an added salt).

Ultrahydrophobicity of Polydimethylsiloxanes-Based Multilayered Thin Films

The formation of polydimethylsiloxanes (PDMSs)-based layer-by-layer multilayer ultrathin films on charged surfaces prepared from water and phosphate buffer solutions has been investigated. The multilayer films prepared under these conditions showed different surface roughness. Nanoscale islands and network structures were observed homogeneously on the multilayer film prepared from pure water solutions, which is attributing to the ultrahydrobic property of the multilayer film. The formation of nanoscale islands and network structures was due to the aggregation of PDMS-based polyelectrolytes in water. This work provides a facile approach for generating ultrahydrophobic thin films on any charged surfaces by PDMS polyelectrolytes.

Specifics of solvation of sulfonated polyelectrolytes in water, dimethylmethylphosphonate, and their mixture: A molecular simulation study

Sulfonated polyelectrolyte membranes (PEMs), such as Nafion and styrene-olefin block copolymers, are explored as permselective membranes for fuel cells as well as suitable barrier materials against chemical agents. The permselective properties of PEM are determined by their microphase segregation into hydrophilic and hydrophobic domains. We performed classical molecular dynamics simulations of solvation of the hydrophilic fragments of PEM exemplified on sulfonated polystyrene (sPS) with potassium, calcium, and aluminum as counterions, in water, phosphor-organic nerve agent simulant dimethylmethylphosphonate (DMMP), and their binary mixture. The force field for the sulfonate group has been developed by optimizing the potential parameters to fit the benzenesulfonate conformations obtained from the density functional theory. For a comparison, we considered perfluorosulfonate oligomers representing fragments of Nafion polymer. We found a noticeable difference between the geometries of the polymer backbone in different solvents. The polymer backbone is stiffer in DMMP for both sPS and Nafion. An anisotropic structuring of the solvent around the phenylsulfonate group is substantially stronger than around the Nafion sidechain due to the rigidity and the anisotropy of the phenylsulfonate group. The counterion significantly affects the conformations of solvated sPS: the rigidity of the backbone increases when potassium or calcium ions are replaced by trivalent aluminum ions.