The salting-out effect and phase separation in aqueous solutions of electrolytes and poly(ethylene glycol)

The compositions of coexisting phases have been determined for aqueous two-phase systems containing poly(ethylene glycol) (PEG) of nominal molecular weight 8000 and a series of eight electrolytes: NaOH, Na₂CO₃, Na₂SO₄, Na₂HPO₄, Na₃PO₄, (NH₄)₂SO₄, MgSO₄, ZnSO₄. The salting-out effects of the electrolytes on the polymer were obtained by fitting a Setschenow-type equation to the tie line data to derive a salting-out coefficient for each electrolyte. For the sodium salts the relative effectiveness of the anions in forming biphasic mixtures follows the Hofmeister series. The relative salting-out effectiveness of the sulphate salts, however, is probably influenced by complexation of the cations by PEG. The values of the salting-out coefficients reflect the extent of preferential hydration of the ethylene oxide units in the polymer chains.     

Synthesis and characterization of cassava starch graft poly(acrylic acid) and poly[(acrylic acid)‐co‐acrylamide] and polymer flocculants for wastewater treatment

Starch‐g‐poly(acrylic acid) and poly[(acrylic acid)‐co‐acrylamide] synthesized via chemically crosslinking polymerization were then each mixed with inorganic coagulants of aluminum sulfate hydrate [Al₂(SO₄)₃·18H₂O], calcium hydroxide [Ca(OH)₂], and ferric sulfate [Fe₂(SO₄)₃] in a proper ratio to form complex polymeric flocculants (CPFs). All CPFs exhibited low water absorbency than those of the uncomplexed superabsorbent copolymers. The color reduction by the CPFs was tested with both synthetic wastewater and selected wastewater samples from textile industries. The synthetic wastewater was prepared from a direct dye in a concentration of 50 mg dm^?3 at pH 7. The CPFs of poly[(acrylic acid)‐co‐acrylamide] with calcium hydroxide at a ratio of 1:2 is the most effective CPF for the wastewater color reduction. The CPF concentration of 500 mg dm^?3 could reduce the color of the synthetic wastewater containing the direct dye solution by 95.4% and that of the industrial wastewater by 76%. Starch‐g‐poly(acrylic acid)/Ca(OH)₂ CPF can reduce the synthetic direct dye and the industrial wastewater by 74% and 18%, respectively. Chemical oxygen demand, residual metal ion concentrations, pHs, turbidity of the wastewater were also investigated and the potential use of the complex polymer flocculants for textile wastewater treatment was indicated. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 2915–2928, 2006     

Unique Solubility of Switchable Alkyl-Amine Surfactants in Water

Because many amine surfactants are soluble in both water and CO₂ phases, they attract interest with regard to stabilizing CO₂-in-water dispersion systems. In our recent research, we find that the solubility of alkyl-amine surfactant in water can be significantly enhanced by salts, even though the salts are usually “salting-out” to other surfactants. The influence of various anions (NO₃⁻, Br⁻, Cl⁻, and SO₄²⁻) and cations (Na⁺, Ca²⁺, and Mg²⁺) on the alkyl-amine surfactants is investigated. The results are contrary to Hofmeister series and show that all the anions can enhance the solubility (salting-in) in the order of: NO₃⁻ > Br⁻ > Cl⁻ > SO₄²⁻, while the impact of the cations is insignificant. A physical–chemistry model based on the switchable property of the surfactant is proposed and well explains the experimental results. Therefore, the switchable alkyl-amine surfactants have potential to be applied under high-salinity and high-temperature conditions, for example, in enhanced oil recovery processes for a hot and salty carbonate reservoir.     

How the Influence of Different Salts on Interfacial Properties of Surfactant–Oil–Water Systems at Optimum Formulation Matches the Hofmeister Series Ranking

In this work, we present the effects of salts on sodium dodecyl benzene sulfonate micellization and on the interfacial performance of a sodium dodecyl benzene sulfonate–heptane–brine system at optimum formulation, i.e., hydrophilic–lipophilic deviation (HLD) = 0. In order to do that, interfacial tension and dilational interfacial rheology properties of surfactant–heptane–water systems at optimum formulation are measured using an interfacial spinning drop tensiometer with an oscillating velocity, which can accurately measure interfacial rheology properties at both low and ultralow interfacial tensions. The brines used contain one of the following salts: MgCl₂, CaCl₂, NaCl, NH₄Cl, NaNO₃, CH₃COONa, or Na₂SO₄. We performed a one-dimensional salinity scan with each of these salts to achieve an optimum formulation. In relation to the Hofmeister series, we found that, at optimum formulation, systems with chaotropic ions (NH₄⁺, NO₃⁻) present interfaces with ultralow interfacial tensions, very low dilational modulus, and a low phase angle, whereas kosmotropic ions (Mg²⁺, Ca²⁺, SO₄⁻²) generate high interfacial tension and high rigidity monolayers. Intermediate ions in the Hofmeister series (Na⁺, CH₃COO⁻, Cl⁻) present interfaces with intermediate properties. Furthermore, according to the Hofmeister series, interfaces can be respectively ordered from higher to lower rigidity for surfactant counterions Mg²⁺ > Ca²⁺ > Na⁺ > NH₄⁺ and coions SO₄²⁻ > CH₃COO^– > Cl⁻ > NO₃⁻, which correspond to a salting-out (highest rigidity) and salting-in (lowest rigidity) effect. We observed that counterions have a more significant effect on surfactant–oil–water system properties than those that act as coions.     

A redox poly(ionic liquid) hydrogel: Facile method of synthesis and electrochemical sensing

In this article, a redox-responsive poly(ionic liquid) (redox-PIL) hydrogel Poly(1-vinyl-3-propionate imidazole phenothiazine sulfonic acid)-chitosan [Poly(VPI⁺PTZ-(CH₂)₃SO₃⁻)-CS] was produced by using chitosan (CS) crosslinking with redox-PIL Poly(1-vinyl-3-propionate imidazole phenothiazine sulfonic acid [Poly(VPI⁺PTZ-(CH₂)₃SO₃⁻)]. The incorporation of redox-active counter anions 3-(phenothiazine-10-yl) propane 1-sulfonic acid anions (PTZ-(CH₂)₃SO₃⁻) into cationic PIL-polyimidazole rendered Poly(VPI⁺PTZ-(CH₂)₃SO₃⁻) with electron catalytic ability, ionic conductivity, and electron conductivity. Poly(VPI⁺PTZ-(CH₂)₃SO₃⁻)-CS combines the properties of hydrogel and redox-PIL, thus offering intrinsic porous conducting frameworks and promoting the transport of charges, ions, and molecules, leading hydrogel with excellent electrochemical properties. The crosslinking occurrence of Poly(VPI⁺PTZ-(CH₂)₃SO₃⁻) and CS resulting from the synthetic process of hydrogel was verified by differential scanning calorimetry and thermogravimetric analysis. A three-dimensional polymer network hydrogel with good biocompatibility and permeability was formed after crosslinking. In addition, only 64% weight loss within 600 °C was observed in Poly(VPI⁺PTZ-(CH₂)₃SO₃⁻)-CS representing its thermally stable performance. When used as an electrochemical sensor, the hydrogel-modified gold electrode improved the electrocatalytic oxidation of cysteine. Differential pulse voltammetry results indicated that the detection range was from 5 × 10⁻⁸ to 5 × 10⁻³ M and the limit of detection was 6.64 × 10⁻⁸ M. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48051.     

Formation of porous aggregations composed of Al2O3 platelets using potassium sulfate flux

Porous aggregations, with about 10 μm diameter, composed of Al₂O₃ platelet crystals were formed by heating a powder mixture consisting of Al₂(SO₄)₃+2K₂SO₄ (mol ratio) in an alumina crucible at temperatures 1000–1300°C for 3 h and removing the flux component with hot hydrochloric acid after heating. The specific surface area of the aggregations obtained by heating at 1000°C for 3 h was maximum and its value was 5·2 m² g⁻¹. Since the size of Al₂O₃ platelets increased and the number of Al₂O₃ platelets decreased, the specific surface area decreased to 0·7 m² g⁻¹ at 1100°C. When heated at 1300°C, the size of the Al₂O₃ platelets increased with increasing amount of K₂SO₄ in the starting powder mixture. ©     

1H NMR,thermal, and conductivity studies on PVAc based gel polymer electrolytes

The lithium‐ion conducting gel polymer electrolytes (GPE), PVAc‐DMF‐LiClO₄ of various compositions have been prepared by solution casting technique. ¹H NMR results reveal the existence of DMF in the gel polymer electrolytes at ambient temperature. Structure and surface morphology characterization have been studied by X‐ray diffraction analysis (XRD) and scanning electron microscopy (SEM) measurements. Thermal and conductivity behavior of polymer‐ and plasticizer‐salt complexes have been studied by differential scanning calorimetry (DSC), TG/DTA, and impedance spectroscopy results. XRD and SEM analyses indicate the amorphous nature of the gel polymer‐salt complex. DSC measurements show a decrease in T_g with the increase in DMF concentrations. The thermal stability of the PVAc : DMF : LiClO₄ gel polymer electrolytes has been found to be in the range of (30–60°C). The dc conductivity of gel polymer electrolytes, obtained from impedance spectra, has been found to vary between 7.6 × 10^?7 and 4.1 × 10^?4 S cm^?1 at 303 K depending on the concentration of DMF (10–20 wt %) in the polymer electrolytes. The temperature dependence of conductivity of the polymer electrolyte complexes appears to obey the VTF behavior. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

A study of phase evolution and crystal growth for nano-sized monoclinic Y4Al2O9 as a novel thermal barrier coatings

Nano-sized monoclinic Y₄Al₂O₉ was produced by sol-gel process as a novel potential candidate material for thermal barrier coatings. The thermal behavior, structural evolution of the products and the morphological characteristics of the compacted bodies were investigated by Thermogravimetric analysis and differential scanning calorimeter (TG-DSC), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and Field emission scanning electron microscopy (FESEM). Qualitative analyses indicate that monoclinic Y₄Al₂O₉ was formed at about 1000 °C, and exhibited good phase stability throughout the annealing temperature ranging from 1000 °C to 1400 °C. The thermophysical properties of Y₄Al₂O₉ ceramics were also evaluated compared with 8YSZ and La₂Zr₂O₇. The determined activation energy of crystal growth is about 72.71 ± 0.31 kJ mol⁻¹. Meanwhile, Y₄Al₂O₉ represents low thermal conductivity (1.71 W m⁻¹ K⁻¹), moderate thermal expansion coefficient (8.73 × 10⁻⁶ K⁻¹), and high sintering-resistance ability. Such results reveal that nano-sized Y₄Al₂O₉ is favorable for the application of TBCs.     

Ionization equilibria in solution of nickel(II) chloride in N,N-dimethylformamide

Visible absorption spectra and the molar conductance curve at NiCl₂ dissolved in dimethylformamide (DMF) have been determined at 25°C. Absorption spectra of ternary system Ni(ClO₄)₂ + Et₄NCl + DMF and NiCl₂ + chlorobenzene + DMF have also been determined at 25°C. It has been found that at lower concentrations of NiCl₂ monochloride nickel complex NiCl(DMF)⁺₅ and outer-sphere ion-pair {NiCl(DMF)⁺₅Cl⁻}⁰ coexist in the solution. The presence of pseudotetrahedral complex NiCl₃DMF⁻ and the existence of coordinative disproportionation equilibrium have been established in the more concentrated solutions of NiCl₂. The formation constant of outer-sphere ion-pair equal to (1.33 ± 0.2) × 10² has been derived from the conductometric data. The equilibrium constant of disproportionation reaction equal to (3.89 ± 0.2) × 10² has been determined on the basis of the absorption spectra of NiCl₂ in DMF.     

Investigation of the effect of agglomeration time, pH and various salts on the cleaning of Zonguldak bituminous coal by oil agglomeration

In this study, the effects of bridging liquid concentration, agglomeration time, pH and various salts on the combustible recovery and ash contents of the agglomerated products have been investigated. Kerosene was used as bridging liquid. The optimum values of kerosene concentration, pH and agglomeration time have been determined as 20 wt%, 7.5 and 15 min, respectively. Metallic salts, such as FeSO₄, NaCl, FeCl₃, Al₂(SO₄)₃ were used in the experiments in which the effects of salts were investigated. While the combustible recovery slightly increased depending on the increase in the concentration of NaCl, very small decreases have been recorded in the recoveries depending on the increase in the concentration of the FeCl₃. A considerable reduction occurs in the agglomeration recovery with the increasing concentration of FeSO₄, while the combustible recovery slightly decreases at low concentration of Al₂(SO₄)₃.     

The conductivity and characterization of the plasticized polymer electrolyte based on the P(AN-co-GMA-IDA) copolymer with chelating group (II): The effect of free ion in the plasticized polymer electrolyte

A new gel-type polymer electrolyte (GPE) was made by the copolymerizing acrylonitrile (AN) and (2-methylacrylic acid 3-(bis-carboxymethylamino)-2-hydroxy-propyl ester) (GMA-IDA). The copolymer mixed with a plasticizer—propylene carbonate (PC) and lithium salt to form GPE. The lithium salts are LiCF₃SO₃, LiBr and LiClO₄. FT-IR spectra show that the lithium ion in the LiClO₄ system has the strongest interaction with the group based on the plasticized polymer. FT-IR spectra also indicate that CF₃SO₃⁻ prefers producing anion-cation association. Moreover, the ¹³C solid state NMR spectra for the carbons attached to the PC of GPE exhibited different level of chemical shift (158.5 ppm) when the different lithium salts were added to the electrolyte. The results of differential scanning calorimeter (DSC) also indicate that the LiClO₄ system has more free lithium ions; therefore, it has the maximum conductivity. In this study, the highest conductivity 2.98 × 10⁻³ S cm⁻¹ exists in AG2/PC = 20/80 wt.% system which contain 3 mmole (g-polymer)⁻¹ LiClO₄. Additionally, the polymer electrolytes, which contain GMA-IDA have better interfacial resistance stability with lithium electrode.     

Soap-based detergent formulations: XXIII. Synthesis of p-sulfobenzyl ammonium inner salts and structural correlation with analogous amphoterics

Two series of p-sulfobenzyl ammonium inner salts, RN⁺(CH₃)₂CH₂C₆H₄SO₃⁻ and RCONH(CH₂)₃N⁺−(CH₃)₂CH₂C₆H₄SO₃⁻, where R is a straight chain alkyl group, were prepared by sulfonation of the corresponding quaternary ammonium chlorides. Although both series have excellent lime soap dispersion properties, the former series gave optimum detergency at considerably shorter alkyl chain length than the latter serires. The detergency, lime soap dispersion ability, and solubility of these compounds were compared with those of structurally analogous aliphatic sulfobetaines. Structural variations, such as length and nature of the bridge between the cationic and anionic groups, length of the lipophilic chain, and insertion of an amidopropyl group into the lipophilic portion of the molecule, significantly altered the detergency and solubility but not the lime soap dispersing ability of the amphoterics.     

Phase behavior and mechanism of formation of protofiber morphology of solution spun poly(acrylonitrile) copolymers in DMF‐water system

Phase diagrams of a series of copolymers of acrylonitrile (AN) and acrylic acid (AAc) were constructed using linearized cloud point correlation. The miscibility region in the phase diagram was found to increase with the increase in AAc content of the copolymers. For various compositions, χ₁₃ (polymer–water interaction parameter) values were estimated by sorption experiment. As the hydrophilic nature of the polymer increased with the increase in the content of acrylic acid, the χ₁₃ interaction parameter was found to decrease from poly(acrylonitrile) homopolymer to its copolymer with 50 mol % acrylic acid (AA50B). The polymer–solvent interaction parameters (χ₂₃) and composition at the critical points for all the polymers were determined by fitting the theoretical bimodal curves to the experimental cloud point curves using Kenji Kamide equations. The polymer composition at the critical point was found to increase by 400% with increasing AAc content. The polymers were solution spun in DMF‐water coagulation bath at 30°C and their protofiber structures were investigated under scanning electron microscopy. The observed morphological differences in protofibers were explained on the changes brought about in the phase separation behavior of the polymer–solvent–nonsolvent systems. The copolymers with higher acrylic acid content could be solution spun into void free homogeneous fibers even at conditions that produced void‐filled inhomogeneous fibers in poly(acrylonitrile) and its copolymers with lower AAc content. The experiments demonstrate the important role of thermodynamics in deciding the protofiber morphology during coagulation process. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Effect of grain size on tribological behavior of hot-pressed boron carbide sliding against alumina balls

Boron carbide ceramics (B₄C) have extraordinary hardness and well-abrasive resistance, while the tribological behavior of ceramic materials is complicated, which are affected by microstructures, mechanical properties, and surface characteristics, and so on. In this paper, the effect of grain size on the mechanical properties especially the wear resistance of hot-pressed B₄C was investigated. The average coefficient of friction of the B₄C/Al₂O₃ friction pair ranges from .41 to .66. The sample with the minimum grain size possesses the lowest wear rate of about 2.15 × 10⁻⁶–7.66 × 10⁻⁶ mm³∙N⁻¹∙m⁻¹. The analysis of the wear rate (W_R) and grain size (G) indicates that the wear resistance (W_R⁻¹) and the reciprocal of the square root of grain size (G^−1/2) are in line with the Hall–Petch relation. Fracture and the resulting abrasive wear are the main wear mechanisms of B₄C in the dry sliding process. This success provides a theoretical basis and a design approach of microstructure to improve the tribological behavior of ceramic materials.     

Evaluation of a modified spray-applied interfacial polymerization method for preparation of nanofiltration membranes

Nanofiltration (NF) membranes were fabricated by using piperazine (PIP) and trimesoyl chloride (TMC) by conventional and spray-applied interfacial polymerization methods, studying the effect of the application method for both phases, the number of applied layers, and the displacement speed for the spray application. A polysulfone ultrafiltration membrane was used as support. NF membranes were characterized by different spectroscopic, microscopic, and physicochemical techniques. Rejection capacity was evaluated for sodium chloride (NaCl), sodium sulfate (Na₂SO₄), and magnesium sulfate (MgSO₄) salts; the decreasing rejection order was Na₂SO₄ > MgSO₄ > NaCl for each NF membrane. NF membrane prepared with one layer of the sprayed out TMC solution and conventional application of PIP solution exhibited the highest salt rejection (99% for 1000 ppm Na₂SO₄) and a permeated flux of 10.28 L m⁻² h⁻¹ at 0.55 MPa. The modified method is a facile-reproducible preparation methodology that reduces the consumption of time, effort, and reagents leading to a scalable manufacturing process for separation technology. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48129.     

Ionization equilibria in solutions of cobalt(II) bromide in N,N-dimethylformamide

Visible absorption spectra and the molar conductance curve of CoBr₂ dissolved in N,N-dimethylformamide (DMF) have been determined at 25°C. Absorption spectra of ternary systems Co(ClO₄)₂ + Et₄NBr + DMF and CoBr₂ + chlorobenzene + DMF have also been determined at 25°C. The results indicate the formation of the CoBr(DMF)⁺₅. CoBr₃DMF⁻ complex electrolyte controlling the electrolytic properties of the solution. The stability constants of the individual bromo-complexes of cobalt(II) have been calculated.     

Novel fluorene-based copolymer with pendant aza-crown ether: Highly sensitive and specific detection for CuSO4 and concurrent effect of anions

A novel fluorene-based copolymer with aza-15-crown-5 as pendant group was synthesized by Suzuki-coupling reaction, and characterized by ¹H NMR, ¹³C NMR, EA, and GPC. The polymer was brightly blue emissive in common organic solvents, such as CHCl₃, CH₂Cl₂, and THF. Fluorescent titration experiments carried out in THF-MeOH system indicate that the polymer has quite good selectivity and high sensitivity for CuSO₄, which is contrasting to the weak responses for other copper salts such as Cu(ClO₄)₂, CuCl₂, Cu(NO₃)₂, and Cu(OAc)₂. Molecular simulation result suggests that this unique phenomenon may come from the synergistic effect of the bivalent counterion SO₄²⁻. This new system utilizing the strong luminescent property of polyfluorene as reporter and concurrent effect of the counterion SO₄²⁻ may be developed as chemosensor for the special detection for CuSO₄.     

Design and construction of two new polymers featuring macrocyclic subunits based on a rigid clamp-like ligand

Reaction of a rigid conjugated clamp-like ligand N,N′-bis(pyridin-3-yl)-2,6-pyridinedicarboxamide (bppdca) with ZnSO₄·7H₂O or CoSO₄·7H₂O resulted in the formation of two new polymers, namely, {[Zn₂(bppdca)(SO₄)₂(DMF)₂]·(DMF)}_n (1) and {[Co(bppdca)(SO₄)(CH₃OH)(DMF)]·H₂O}_n (2). Both 1 and 2 feature one-dimensional double-chain structures with macrocyclic subunits, and the chains further self-assemble into a higher-dimensional framework via the hydrogen-bonding and π–π stacking interactions. Fluorescence studies show that the free ligand displays a strong fluorescence emission in solid state at room temperature, but in 1 and 2, the complexation of the ligand with metal ions and weak intermolecular interactions make the fluorescence emission partial quenching.     

Impact of the aluminum sulfate 18-hydrate particle size on the coordination crosslinking behaviors of acrylonitrile–butadiene rubber–aluminum sulfate 18-hydrate composites

In this study, aluminum sulfate 18-hydrate [Al₂(SO₄)₃·18H₂O] particles of different sizes, which were obtained via high-energy ball-milling technology, were successfully compounded with acrylonitrile–butadiene rubber (NBR) to fabricate crosslinked rubber composites. The results suggest that high-energy ball milling had no significant change on the crystal structure of Al₂(SO₄)₃·18H₂O, but it significantly reduced the particle size. The effects of the particles size on the coordination crosslinking behaviors and mechanical properties of the NBR–Al₂(SO₄)₃·18H₂O composites were fully explored. The coordination crosslinking reaction was demonstrated to occur between the nitrile group (─CN) and Al(III). Moreover, with the decreasing particle size, the composites achieved a better interfacial adhesion and more crosslinking points, and this led to significant increases in the crosslinking density and the mechanical properties. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47717.     

Effect of reaction medium on radical copolymerization of acrylonitrile with vinyl acids

Radical polymerization of acrylonitrile (AN) with methacrylic acid (MAA) and itaconic acid (IA) was carried out in a mixture of dimethylformamide (DMF) and water at 70°C using α, α′‐azobisisobutyronitrile (AIBN) as an initiator. Monomer feed in the polymerization vessel was 98:2 (AN:MAA/IA) in the molar ratio, and the DMF:H₂O ratio was varied between 20:80 and 80:20 (w/w). Copolymers were characterized by FTIR, carbon, hydrogen, nitrogen elemental CHN analysis, ¹H‐ and ¹³C‐NMR, and viscometry. The rate of polymerization (R_p) was found to decrease with an increase in DMF concentration in the reaction medium, that is, in 20% DMF for AN–MAA system, the R_p is 1.23% min⁻¹ in 1 h of polymerization, while in 80% DMF, R_p is reduced to 0.37% min⁻¹. The nature of the vinyl acid also affects the R_p. It has been shown that the rate of polymerization is higher for an AN–MAA system as compared to an AN–IA system (R_p = 1.0% min⁻¹) and the methacrylic or itaconic acid content in the copolymer increases with an increase in the DMF concentration. The MAA content in the poly(AN–MAA) polymer produced in 20% DMF is 3.2 mol %, which increases to 6.1 mol % (calculated through FTIR spectra) when DMF is increased to 80% in the reaction medium. The intrinsic viscosity [η] of the poly(AN–IA) and poly(AN–MAA) copolymers in DMF was found to be in the range of 0.67–2.90 dLg⁻¹ depending on the reaction medium. In determining the intrinsic viscosity, a definite deviation from rectilinearity of the concentration dependence in the high‐dilution region is observed, thereby demonstrating the polyelectrolyte behavior of these polymers. Through FTIR and NMR spectral studies, PAN homopolymer and other copolymers have shown the formation of a small quantity of acrylamide units. In addition copolymer P₁₀, which contains 10.1 mol % IA, has shown anhydride formation. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1640–1652, 2001