Aggregation Behavior of Pluronic-L64 in Presence of Sodium Dodecyl Sulphate in Water

The effect of sodium dodecyl sulfate (SDS) on the micellization and aggregation behavior of a poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) (PEO-PPO-PEO) amphiphilic copolymer (Pluronic L64: EO₁₃ PO₃₀ EO₁₃) have been investigated by various techniques like, cloud point, viscosity, isothermal titration calorimetry (ITC), differential scanning calorimetry (DSC), fluorescence spectroscopy, room temperature phosphorescence (RTP), and small angle neutron scattering (SANS). Addition of SDS in L64 solutions shows mark alteration of different properties. We observed synergistic interaction between SDS and Pluronic L64. The changes in the critical micelle concentration (CMC), critical micelle temperature (CMT), cloud point (CP), micelle size, and shape has been correlated and reported in terms of structure dynamics and mechanics. The ITC titrations have been used to explore the different stages of binding and interactions of SDS with L64. The enthalpies of aggregation for copolymer-SDS aggregates binding, organizational change of bound aggregates, and the threshold concentrations of SDS in the presence of copolymer were estimated directly from ITC titration curves. The effect of temperature on enthalpy values has been reported in terms of different aggregation state. Fluorescence and RTP for L64 were used to investigate the change in micellar environment on the addition of SDS at different temperature. Appearance and shifting of SANS peaks have been used to monitor the size and inter micellar interaction on addition of SDS in L64 solution. Cloud point and viscosity elaborate the penetration of SDS molecule in L64 micelle and hence changing the micellar architect.     

线球状银颗粒的液相合成及其机理研究

本文在三嵌段共聚物Pluronic F127/十二烷基硫酸钠(SDS)混合表面活性剂体系中制备了直径为 3～4 μm的线球状 Ag 颗粒。实验发现随着体系中SDS浓度的增加,组成Ag微球的亚单元从椭球状经由棒状变成了纳米线。动态光散射数据表明随着SDS的加入,F127胶束被F127/SDS混合胶束所取代,且混合胶束尺寸随着SDS浓度的变化而变化。实验表明SDS的烷基链段与F127的憎水PPO链段的相互吸引作用,以及SDS亲水基团之间的静电排斥作用将影响产物的最终结构。     

Salt influence in the polymer-surfactant interaction in solution. A fluorescence probe investigation of the EHEC/SDS/ water system

 The effect of small amounts of salt on the interaction between two fractions of ethyl(hydroxy)ethyl cellulose, EHEC, and sodium dodecyl sulfate, SDS, has been investigated by means of steady-state fluorescence measurements. The two polymer fractions display different properties in hydrophobicity expressed as different cloud points. The results are discussed in relation to hydrodynamic (viscosity) and thermodynamic (equilibrium dialysis) properties. The micropolarity as sensed by the probe pyrene shows that the polymers begin to interact with SDS at a lower concentration in the presence of salt. The average aggregation numbers of polymer-bound clusters, N _p, were obtained by fluorescence-quenching data in combination with equilibrium dialysis experiments. N _p was found to increase in the presence of salt for the EHEC fraction with a high cloud point (CP). The polymer with a low CP displays higher N _p in the presence of salt at low SDS concentrations, but exhibit lower N _p at higher SDS concentrations than in the salt-free system. The microviscosity index as determined by intramolecular excimer formation of 1, 3-di(1-pyrenyl)propane (P3P) is highest for the lowest N _p and there is a corre-lation with N _p in the presence as well as absence of salt for both EHEC fractions. It is found that when the same fractional amount of SDS is bound to the polymers, 10–20% of the value of saturation, the increase in macroviscosity occurs and the microviscosity shows high rigidity. Received: 3 March 1997 Accepted: 23 May 1997     

INDUCTION OF CRYSTALLIZATION OF SPECIFIC CALCIUM OXALATE HYDRATES IN MICELLAR SOLUTIONS OF SURFACTANTS

ABSTRACT

The influence of octaethylene glycol mono-n-hexadecyl ether (C₁₆EO₈) and sodium dodecyl sulphate (SDS) on the crystallization of calcium oxalate from 0.3 mol dm^?3 sodium chloride solutions has been investigated. The critical micellar concentration (CMC) of C₁₆EO₈ in water and 0.3 mol dm^?3 NaCl was determined by surface tension measurements (CMC_H2O=CMC_NaCl = 7.2.10^?6 mol dm^?3). The kinetics of precipitation of calcium oxalate was followed by Coulter counter, and solid phases were characterized by polarized microscopy, thermal analysis and X-ray powder diffraction patterns. Under the precipitation conditions employed, the thermodynamically stable monohydrate, CaC₂O₄?H₂O (COM) was the predominant crystalline form. In the presence of micellar solutions of C₁₆EO₈ precipitation of this phase was facilitated as evidenced by higher initial precipitation rates and higher precipitate volume and number of particles, as compared to the controls. Micellar solutions of 50S retarded precipitation but induced crystallization of calcium oxalate dihydrate, CaC₂O₄?(2+×)H₂O (COD, x≤0.5). Thus at c(SDS>CMC the precipitates contained ≥85 mass % COD. The results are discussed in relation to previously reported data on the precipitation of calcium oxalate in the presence of dodecyl ammonium chloride     

Microcalorimetric Study on Interaction between PEO‐PPO‐PEO Triblock Copolymers and Sodium Dodecyl Trioxyethylenated Sulfonate in Aqueous Solutions

Interactions between three triblock copolymers of poly (ethylene oxide)‐poly (propylene oxide)‐poly (ethylene oxide), EO_mPO_nEO_m, and the ionic surfactant sodium dodecyl trioxyethylenated sulfonate, C₁₂E₃S, in aqueous solutions were investigated with titration microcalorimetry at 293.15 K. Values of enthalpies, entropies, and free energies of interaction have been derived. The thermodynamic data indicate that interactions between EO_mPO_nEO_m and C₁₂E₃S decrease with the increase of m/n.     

Effects of Surfactants on Phase Transition of Poly(N-isopropylacrylamide) and Poly(N-isopropylacrylamide-co-dimethylaminoethylmethacrylate)

The effect of surfactants on the phase transition of poly(N-isopropylacrylamide) (PNIPAM) and poly(N-isopropylacrylamide-co-dimethylaminoethylmethacrylate) (P(NIPAM-co-DMAEMA)) was extensively investigated by a turbidometry. When the concentration of cetyltrimethyl ammoniumchloride (CTAC) increased from 0.01 to 0.32%, the cloud point of PNIPAM increased from 32 to 38.5°C. When the concentration of sodium dodecyl sulfate (SDS) increased from 0.01 to 0.08%, the cloud point increased from 32.5 to 38°C. The cloud points with SDS were higher than the values obtained with CTAC. In addition, SDS suppressed the temperature sensitivity much more effectively than CTAC did. The adsorption of the ionic surfactants (CTAC, SDS) on the polymer chains may account for the increase in the cloud point. On the other hand, Tween 20 had little effect on the cloud point and the temperature sensitivity of the homopolymer, possible because it is nonionic. The effect of surfactants on the phase transition of P(NIPAM-co-DMAEMA) exhibited a trend similar to the effect on the phase transition of PNIPAM.     

Aqueous foam stabilized by polyoxyethylene dodecyl ether

Foaming properties of aqueous solutions of the nonionic surfactant polyoxyethylene dodecyl ether (C₁₂EO _n ) were studied at 298 K. Four different EO chain lengths, namely C₁₂EO₃, C₁₂EO₅, C₁₂EO₇, and C₁₂EO₉, were considered. The foams obtained from C₁₂EO₃ or C₁₂EO₅ were extraordinary stable retaining a constant volume for more than 20 h. The presence of lamellar liquid crystalline phases was mainly responsible for the super-stable aqueous foams.     

Salt‐Induced Micellization of Pluronic F88 in Water

The effect of potassium chloride on the micellization of a poly(ethylene oxide)‐poly(propylene oxide)‐poly(ethylene oxide) (PEO‐PPO‐PEO) triblock copolymer (Pluronic F88: EO₁₀₃PO₃₉EO₁₀₃.) in water was studied by fluorescence, FTIR, ¹H NMR, dynamic light scattering, and dye solubilization. The critical micellization temperature (CMT) values of the copolymer decreased with an increase of KCl concentration while micellar core gets progressively dehydrated. The results reveal the leading role of salt‐water interaction in promoting the micellization of PEO‐PPO‐PEO copolymer by the addition of salt. No significant micellar growth was seen even at temperatures close to cloud point.     

Phase conditions,hydrodynamic features and salt influence in the polymer-amphiphile interaction for the EHEC/SDS/water system

Two fractions of ethyl(hydroxy)ethyl cellulose, EHEC, and their interactions with sodium dodecyl sulphate, SDS, have been investigated. The effect of salt on these interactions was explored. The more hydrophobic fraction exhibits a cloud point (CP) of 30°C, and the more hydrophilic fraction has a CP around 65°C. The properties of the systems were studied by means of hydrodynamic (viscosity), equilibrium dialysis and cloud point measurements. Dye solubilization was used to obtain indications of cluster formation on the polymer backbone. The equilibrium dialysis shows a steep binding beginning at a critical surfactant concentration indicating a cooperative effect in the EHEC/SDS/water system. It is found that when the degree of binding is moderate and only 10–20% of the value at saturation, the specific viscosity effects occur and solutions containing high polymer concentrations pass a marked maximum in viscosity. It is shown that the maximum in viscosity and the collcoil interaction, expressed as Huggins constant,k _H, appear a composition with the same fractional amount of SDS adsorbed to both EHEC fractions. It was found that the onset of redistribution and increase in viscosity were shifted to higher SDS concentrations, although still below the normal CMC, for the EHEC fraction with a high CP. When small amounts of salt are present in the EHEC/SDS/water solutions, the CP curves develop a pronounced minimum at low SDS concentrations. The redistribution of SDS to the polymers starts immediately in the presence of salt, but the viscosity of the solutions is affected only in a very narrow composition interval.     

Interaction and solubilization of some phenolic antioxidants in Pluronic® micelles

The solubilization of four phenolic antioxidants, namely p-hydroxybenzoic acid (PHBAA), syringic acid, sinapic acid, and quercetin in micelles of an ethylene oxide (EO)–propylene oxide (PO) triblock copolymer Pluronic^® P104 (EO₂₇–PO₆₁–EO₂₇, PPO mol wt = 3540, % PEO = 40) was examined at different temperatures, pHs, and in the presence of sodium chloride. The nano-size core–shell micelles of P104 characterized by dynamic light scattering had hydrodynamic diameter of about 18–20 nm with low polydispersity. Antioxidants induced micellization and micellar growth were observed. The critical micellar concentration (CMC), critical micellar temperature (CMT), cloud point (CP) of P104 decreased due to solubilization and interactions of antioxidants. The solubilization was favored at higher temperature, pH and in the presence of salt and follows the order PHBA > syringic acid > sinapic acid > quercetin which corresponds to the trend in their aqueous solubility. The location of antioxidant in micelles observed from NOESY spectra. Structure and hydrophobicity of antioxidants were found to be governing factors for their interaction and location in the micelles.     

Micellization of sodium dodecyl sulfate and polyoxyethylene dodecyl ethers in solution

The effect of polyoxyethylene type nonionic surfactants (C₁₂E _n n = 3, 4, 5, 6, 7 and 8) on the aqueous solution of sodium dodecyl sulfate (SDS) in absence and presence of NaCl was examined using small-angle neutron scattering (SANS), dynamic light scattering (DLS), and viscosity measurements. Upon addition of C₁₂E _n , micellar size of SDS was found to increase significantly, and such micellar elongation was further enhanced in the presence of NaCl. Micellar growth is most significant in presence of shorter moieties of C₁₂E _n (e.g., n = 3, 4) as compared to higher ethereal oxygen content. The results of structural investigations with SANS and DLS to confirm this assumption are reported. The cloud point of C₁₂E _n has increased upon addition of SDS and decrease with NaCl, and a typical behavior is observed when both SDS and NaCl were present.     

Thermosensitive properties of a novel poly(methyl 2-acetamidoacrylate-co-methyl acrylate)

Copolymerizations of methyl 2-acetamidoacrylate (MAA) with methyl acrylate (MA) were carried out at 60 °C in chloroform. MAA-rich copolymers are soluble in water and MAA-poor copolymers insoluble. Among water-soluble copolymers obtained, only one (HP-77) which contains 77% of MAA units was thermosensitive. Thermal properties of HP-77 were investigated in the presence or absence of inorganic salts. The cloud point of aqueous HP-77 solution depended on polymer concentration: The cloud point decreased exponentially with an increasing concentration of the polymer. The cloud point of HP-77 was also affected significantly by the type and concentration of salts. The effectiveness of salts to reduce the cloud point is NaBr≈KBr<NaCl≈KCl<Na₂SO₄≈K₂SO₄. The salting-out coefficients were evaluated as 2.45 l/mol for sodium chloride and 14.56 l/mol for sodium sulfate, respectively, from the relationship (Setschenow's equation) between logarithm of the solubility of HP-77 and salt concentration. The salting-out coefficient of sodium sulfate is larger than that of sodium chloride.     

Effects of additives on the cloud points of selected nonionic linear ethoxylated alcohol surfactants

Effects of various additives including inorganic salts, nonionic and ionic surfactants, water-soluble polymers and alcohols on the cloud points of three linear nonionic surfactants, Tergitol 15-S-7, Tergitol 15-S-9 and Neodol 25-7, were investigated. These surfactants are readily biodegradable and either linear primary or secondary ethoxylated alcohols. Cloud points of these surfactants were functions of their concentrations and concentrations of additives. The cloud points of nonionic surfactant mixtures lay in between the cloud points of individual component surfactants. Presence of two ionic surfactants, sodium dodecyl sulfate (SDS) and cetyl trimethyl ammonium bromide (CTAB), increased the cloud point of 1 wt% Tergitol 15-S-7 micellar solution dramatically when concentrations of ionic surfactants approaching their critical micelle concentration. Addition of water-soluble polymers decreased the cloud point, while addition of inorganic salts can either increase or decrease the cloud points. However, the effect of an alcohol additive on cloud point was dependent on its chain length or its water solubility. Interestingly, synergistic effects between sulfate or phosphate and pentanol on depression of cloud points of Tergitol 15-S-9 were discovered. A linear model predicting cloud points of Tergitol 15-S-X (X = 7, 9 and 12) surfactants and Neodol 25-X (X = 7, 9 and 12) surfactants were proposed with a correlation to logarithm of their ethylene oxide numbers.     

Temperature-driven Precipitation of poly(N-isopropylacrylamide-co-methacrylic acid) in Cationic,Anionic and Nonionic Surfactant Solutions

The temperature-driven precipitation of poly(N-isopropylacrylamide-co-methacrylic acid) (P(NIPAM-co-MAA)) in anionic, cationic, and non-ionic surfactants solutions was investigated under an acidic (e.g. pH 3.0) and an alkali condition (pH 9.0). Under the acidic condition, sodium dodecyl sulfate (SDS, anionic) and cetyltrimethylammonium chloride (CTAC, cationic) increased the cloud point of the copolymer and they suppressed the temperature-sensitivity. Under the alkali condition, SDS suppressed the temperature sensitivity as under the acidic condition, but CTAC boosted the temperature sensitivity and it decreased the cloud point of the copolymer. The effect of CTAC on the phase transition under the alkali condition was opposite to the effect observed under the acidic condition. Tween 20 (non-ionic) had little effect on the cloud point and the temperature-sensitivity under both the acidic and the alkali conditions.     

Cloud Point Studies of Tween and Glycol in the Presence of Salts

This article deals with the cloud point studies of ethoxylated sorbitan ester, Tween in the presence of glycols, and salts. Cloud point temperature of Tween 20 (5 mol dm^?3) and Tween 80 (1 mol dm^?3) has been determined in the presence of various salts in addition to glycols. The glycols chosen for these studies were triethylene glycol (TEG), and ethylene glycol mono butylether (EGMBE). At concentration below 0.02 M these salts have no significant effect on cloud point temperature in all cases. The cloud point temperature of Tween+TEG and Tween+EGMBE found to decrease in the presence of sodium chloride (NaCl) and potassium chloride (KCl). The cloud point temperature of Tween 20 + TEG and Tween 20 + EGMBE found to increase in the presence of urea and nicotinamide. The change in cloud point was found to be more in case of nicotinamide as compare to urea. The influence of an additive on the cloud point depends on how it affects the intermicellar interactions. An effort has been made to understand the interaction between solvent and additives leading to a change in solubility of Tween.     

Cloud point extraction of 99Mo with Triton X-114

This paper reports the cloud point extraction (CPE) extraction behaviour of ⁹⁹Mo in non-ionic Triton X-114 (TX-114), sodiumdodecyl sulphate (SDS) + TX-114 and sodium diethyldithiocarbamate (DDTC) + TX-114. The high extraction of ⁹⁹Mo observed in all the CPE systems in pH 5 or less. The extent of extraction was almost unchanged with addition of SDS and DDTC in TX-114. Extraction behaviour was also studied in presence of common salts. It was observed the presence of salts dramatically decreased the amount of molybdenum extraction in the surfactant-rich phase.     

Phase Behavior of Poly(Oxyethylene)–Poly(Oxypropylene)–Poly(Oxyethylene) Block Copolymer in Water and Water–C12EO5 Systems

Abstract

The binary phase diagram of a triblock copolymer poly(oxyethylene) (PEO) poly(oxypropylene) (PPO) poly(oxyethylene) (PEO), (PEO)₃₇(PPO)₅₈(PEO)₃₇ or P105 in water and the ternary system of P105, water, and pentaoxyethylene dodecyl ether (C₁₂EO₅) has been studied to understand the miscibility of a small amphiphile, C₁₂EO₅ and a copolymer, as well as the mixing effect on the formed liquid crystalline structures. Phase diagrams, small angle x‐ray scattering (SAXS) and differential scanning calorimetry (DSC) were used to characterize these systems. The phase diagram of the binary system is presented together with the characteristic parameters for founded phases, namely, cubic, hexagonal, and lamellar phases. In the ternary system it was found that the small amphiphile and the block copolymer, despite having very different chain lengths are essentially miscible forming single phases. A large amount of C₁₂EO₅ can be solubilized in the P105 aggregates whereas P105 is most difficult to dissolve in the C₁₂EO₅ aggregates because of the difference in the molecular size. The copolymer is practically insoluble in the lamellar phase of C₁₂EO₅ due to the packing constraint. Hence, two lamellar phases coexist in a surfactant‐rich region, at W _s  = 0.66, where W _s is the weight fraction of the total amphiphile in the system. This indicates that the thickness of the lipophilic part of the C₁₂EO₅ lamellar phase is too small to allocate the large lipophilic chain of the P105 triblock copolymer.     

Effect of salts and sodium dodecyl sulfate on chaperone activity of camel αS1-CN: Insulin as the target protein

In this study camel αS₁-casein (αS₁-CN) was purified, using a two-step purification procedure. The anti-aggregation (chaperone-like) ability of the purified protein sample was examined in a wide range of experimental conditions and at different concentrations of camel αS₁-CN, in the presence of salts and sodium dodecyl sulfate (SDS). To examine chaperone-like activity of camel αS₁-CN, bovine pancreatic insulin was used as the target protein. Insulin aggregation performed chemically in the presence of 20 mM dithiotreitol (DTT) and was studied at 360 nm wavelength by UV–vis spectrophotometer. Camel αS₁-CN exhibited a dose-dependent chaperone-like activity as the molar ratios of chaperone/target protein varied between 0 and 0.07. The presence of salts or surfactants changing the protein properties had an influence on chaperone capacity of camel αS₁-CN. The results of UV–visible and fluorimetric measurements indicated that the salts neutralize the chaperone-like activity of casein due to dehydration effect and the increased association and aggregation of proteins, while SDS plays a role as chaperone and chaperone-like properties of camel αS₁-CN enhanced in the presence of SDS due to the binding of the hydrophobic tail of SDS and αS₁-CN to the exposed hydrophobic sites of insulin strongly preventing aggregation of insulin.     

Investigation of aqueous foam stability containing pigment colorant using polyoxyethylene nonionic surfactant

To improve foam stability in pigment foaming dispersions, a series of fatty alcohol polyoxyethylene ether (CmEOn) with different alkyl chain and ethylene oxide (EO) chain length (m = 12, 14, 16 and n = 5, 7, 9) were used as foam stabilizer to select the most superior structure for stabilizing foam. The effects of CmEOn on surface tension were investigated which revealed that the CMC of CmEOn in the pigment foaming dispersion decreased with the increase of surfactant hydrophobicity or the decrease of hydrophilicity. Compared to the alkyl chain, EO chain length influenced foam more significantly. C₁₄EO₅ in the pigment foaming dispersion showed lowest CMC and equilibrium surface tension. The presence of wormlike micelles and lamellar liquid crystal of SDS and C₁₄EO₅ endowed the C₁₄EO₅ pigment foaming dispersion with highest viscosity which was distinctly different with other CmEOn. C₁₄EO₅ showed the most superior stabilization effects with foam half-life of 172.9 min at 9 wt%. To further analyze the stabilization mechanism of C₁₄EO₅, the foam volume and bubble diameter change were observed with a digital microscope. The results demonstrated that the superior stabilization effects of C₁₄EO₅ were closely related to its high viscosity, which mainly resulted in the decrease of foam drainage and gas permeability. C₁₄EO₅, the optimal CmEOn structure for stabilizing foam, shows excellent foam stabilization capability in pigment foaming dispersions, which is a promising tool to realize pigment foam coloring.     

Mono- and Di-valent Salts as Modifiers of PEO-PPO-PEO Block Copolymer Interactions with Silica Nanoparticles in Aqueous Dispersions

Colloidal stabilization of nanoparticle dispersions is central to applications including coatings, mineral extraction, and dispersion of oil spills in oceanic environments, which often involves oil-mineral-aggregates (OMAs). We have an ongoing interest in the modulation of amphiphile micellization and adsorption behavior in aqueous colloidal dispersions in the presence of various additives. Here we evaluate the effect of added salts CaCl₂, MgCl₂, and NaCl on the micellization and adsorption behavior of the poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer Pluronic P105 (EO₃₇PO₅₆EO₃₇). In 0.10 wt% silica nanoparticle (10.6 nm average diameter) dispersion, adsorbed block copolymer layer formation begins at a critical surface micelle concentration (csmc) of 0.02 wt%, well below the critical micellization concentration of Pluronic P105 in water. Dye solubilization experiments demonstrate an increase in the csmc upon addition of each salt. Each added salt reaches a level of maximum effectiveness in its ability to disfavor Pluronic P105 adsorption at the silica surface. These peak levels occur at concentrations of 0.005, 0.03, and 0.05 M for CaCl₂, MgCl₂, and NaCl, respectively, in the presence of 0.10 wt% silica nanoparticles. We explain these results in the context of an electrostatic displacer mechanism and discuss possible connections to OMA-dispersant formation.