Water Polyethylene Glycol Research Articles

Effect of Phosphate Concentration on the Corrosion of Iron in Water—Polyethylene Glycol Mixtures

Abstract Various electrochemical measurement techniques (polarization, electrochemical impedance spectroscopy [EIS], and electrochemical quartz microbalance [EQCM]) and accelerated corrosion tests were used to show that phosphates can be used as iron corrosion inhibitors in 20% polyethylene glycol (PEG 400) solutions. Their action mechanisms were found to modify the anodic behavior of the iron. In solutions with low-phosphate concentrations (<5 × 10−3 M), an iron oxide film formed, as in the case of aqueous solutions. But this oxide film did not provide protection and pitting occurred. At a phosphate concentration of 5 × 10−3 M or more, the iron was protected but by a film that was different from the one observed in aqueous solutions. A deposit, composed of PEG and phosphates, adsorbed preferentially on the anodic sites of the iron.

The Characterization and Cytotoxicity of Mixed PEG-DSG Modified Liposomes

It is known that polyethyleneglycol (PEG) modification of the liposome surface leads to the formation of a fixed aqueous layer around the liposomes due to interaction between the PEG polymer and water molecules, which prevents the attraction of opsonins. When a combination of PEG-distearolyglycerol (PEG-DSG) whose characteristics are remarkably different is used, interaction between molecules occurs, leading to increased fixed aqueous layer thickness (FALT). From this speculation, we studied the effect of both modification of PEG900-DSG and PEG2000-DSG modified liposome on FALT, cell uptake and biodistribution. The FALT of mixed PEG modified liposome increased, compared to that of each single PEG modified liposome. In this mixed modification, maximum FALT was shown at liposome modified by added PEG-2000:PEG-900=2:1. This most suitable additional ratio was equal to actual incorporated ratio. On the other hand, cell uptake of mixed modified liposome containing doxorubicin (DOX) was similar with that of PEG2000 modified liposome. Furthermore, mixed PEG modification of liposome was tendency to increase cytotoxicity, compared to that of other modifications. After DOX contained liposome treatment, DOX distribution in the tumor and antitumor activity of DOX increase by mixed PEG modification. In conclusion, it was suggested that mixed PEG liposome (PEG-2000:PEG-900=2:1) was useful for cancer chemotherapy.

Low-flow limit in slot coating of dilute solutions of high molecular weight polymer

Slot coating is a common method in the manufacture of a wide variety of products. It belongs to a class of coating method known as premetered coating: the thickness of the coated liquid layer in principle is set by the flow rate fed to the die and the speed of the substrate moving past, and is independent of other process variables. Thus, premetered methods are ideal for high precision coating. An important operating limit of slot coating is the minimum thickness that can be coated at a given substrate speed, generally referred to as the low-flow limit. The mechanism that defines this limit balances the viscous, capillary and inertial forces in the flow. Although most of the liquids coated industrially are polymeric solutions and dispersions that are not Newtonian, previous analyses of the low-flow limit in slot coating dealt only with Newtonian liquids. In this paper, the low-flow limit in slot coating of an extensional thickening polymer solution is examined both by theory and by experiment. The continuity and momentum equations coupled with an algebraic non-Newtonian constitutive equation that relates stress to the rate-of-strain and relative-rate-of-rotation tensors were solved by the Galerkin/finite element method to model the flows. The flows themselves were visualized by video microscopy and the low-flow limit was found by observing, at given substrate speed, the feed rate at which the flow becomes unstable and breaks up. Various solutions of low molecular weight polyethylene glycol (PEG) and high molecular weight polyethylene oxide (PEO) in water were used in order to evaluate the effect of mildly viscoelastic behavior on the process. At the concentration level of the high molecular weight polymer explored here, the viscoelastic behavior of the solutions could not be accessed by oscillatory tests; the only measurable response to the addition of PEO was the rise of the apparent extensional viscosity.

Low-flow limit in slot coating of dilute solutions of high molecular weight polymer

Slot coating is a common method in the manufacture of a wide variety of products. It belongs to a class of coating method known as premetered coating: the thickness of the coated liquid layer in principle is set by the flow rate fed to the die and the speed of the substrate moving past, and is independent of other process variables. Thus, premetered methods are ideal for high precision coating. An important operating limit of slot coating is the minimum thickness that can be coated at a given substrate speed, generally referred to as the low-flow limit. The mechanism that defines this limit balances the viscous, capillary and inertial forces in the flow. Although most of the liquids coated industrially are polymeric solutions and dispersions that are not Newtonian, previous analyses of the low-flow limit in slot coating dealt only with Newtonian liquids. In this paper, the low-flow limit in slot coating of an extensional thickening polymer solution is examined both by theory and by experiment. The continuity and momentum equations coupled with an algebraic non-Newtonian constitutive equation that relates stress to the rate-of-strain and relative-rate-of-rotation tensors were solved by the Galerkin/finite element method to model the flows. The flows themselves were visualized by video microscopy and the low-flow limit was found by observing, at given substrate speed, the feed rate at which the flow becomes unstable and breaks up. Various solutions of low molecular weight polyethylene glycol (PEG) and high molecular weight polyethylene oxide (PEO) in water were used in order to evaluate the effect of mildly viscoelastic behavior on the process. At the concentration level of the high molecular weight polymer explored here, the viscoelastic behavior of the solutions could not be accessed by oscillatory tests; the only measurable response to the addition of PEO was the rise of the apparent extensional viscosity.

Zirconium-containing mesoporous silica Zr-MCM-48 for alkali resistant filtration membranes

Zirconium-containing mesoporous silica (Zr-MCM-48) membranes were synthesized on a porous alumina support from an aqueous solution containing tetraethylorthosilicate (TEOS), zirconium propoxide (ZrPr) and cetyltrimethylammonium bromide (C 16TAB). The Zr-MCM-48 membranes show high resistance in alkaline solutions at pH 9–12 although the structure of the pure silica MCM-48 membranes collapsed even at pH 10. Zirconium species is considered to present near the pore surface of MCM-48 because the reactivity of ZrPr with surfactant (C 16TAB) molecules is much higher than TEOS in the starting solution. Zr-MCM-48 shows more stable in alkaline solutions than Ti-containing MCM-48 (Ti-MCM-48). The gas permeation and permporometry measurements suggest that there are no large pinholes and cracks in the Zr-MCM-48 membranes. From permporometry the average pore size of the Zr-MCM-48 membrane is estimated to be 2.5 nm. The filtration of polyethylene glycol (PEG) in water shows that the membranes has molecular weight cutoff (MWCO) of about 3800 u. The corresponding molecular size is 2.3 nm. The sharp increase in the rejection of PEG with increase in molecular weight shows narrow pore size distribution of the membrane. These results show that Zr-MCM-48 membranes have great potential for nanofiltration and ultrafiltration with high performance.

Study of the corrosion layer on iron obtained in solutions of water-polyethylene glycol (PEG 400)-sodium phosphate

The iron behaviour in phosphate/water/polyethylene glycol (PEG) was studied in-situ and ex-situ by spectrometry Raman, ESCA spectroscopy, X-ray diffraction, Auger spectroscopy were used as surface analysis methods. It changes with phosphate concentration. At low phosphate concentration (5 × 10−4 M-10−3 M-5 × 10−3 M), iron is corroded. The thin corrosion layer is a mixture of iron oxides (γ-Fe2O3, Fe3O4) and iron phosphate(Fe3(PO4)2, 8H2O). At high phosphate concentration (10−2 M-5 × 10−2 M), the iron is protected. The protection could be due to an heterogenous layer containing PEG 400 and phosphates.

Mechanism of iron corrosion in water–polyethylene glycol (PEG 400) mixtures

The properties of water–polyethylene glycol (PEG 400) solutions vary with the PEG content. The highest acidity and conductivity values were observed in 20% PEG 400 solutions. Oxygen solubility in such solutions decreased as the PEG 400 content increased. Adsorption of PEG 400, estimated by EQCM, varied with the PEG 400 concentration, also reaching a maximum in 20% PEG 400 solutions, with the weight of the adsorbed layer reaching 3.5 μg cm −2. Iron corrosion in water–PEG 400 solutions was studied by monitoring the corrosion potential and the polarization curves. Iron corrosion was highest in the 20% PEG 400 solution due to the compromise between the evolution of acidity, dissolved oxygen content and the adsorption and complexation properties of the PEG solutions. Through adaptation of the Bockris mechanism, PEG adsorption at the metal surface constituted the first stage in the iron corrosion mechanism. Iron (ions)/PEG complexes were then formed, which diffused in solution.

Phase Formation in Extraction of Metals from Aqueous Salt Solutions with Polyethylene Glycol: 2. Polyethylene Glycol-Water Binary System

The experimental data on water activity in PEG solutions as influenced by the PEG concentration and its molecular weight were analyzed in terms of the polymer solution theory. This analysis shows that nonideality of PEG-water solutions is mainly caused by the athermal effect, namely, by a large difference in the size of water and PEG molecules which, according to Flory theory, causes the increase in the entropy of mixing. The influence of van der Waals interactions and hydration on the solution nonideality was also considered. The PEG hydration number is 2 at the critical temperature of formation of the two-phase system and increases to 4 at lower temperatures. Adequate simulation of the nonideality of the systems concerned is reached with the finite value of the coordination number. In spite of weakness of the van der Waals interactions in the PEG-water systems, their contribution to the nonideality is sufficient to provide a two-phase system. The phase diagrams of the PEG-water system at elevated temperatures are discussed.

Experimental sodium phosphate and polyethylene glycol induce colonic tissue damage and oxidative stress.

Bowel washout solutions may damage colonic mucosa and cause shallow ulceration, which may result in diagnostic errors and complications. The effects of polyethylene glycol (PEG) and sodium phosphate on rat colon were investigated histologically and by measurement of indicators of oxidative stress. Thirty Wistar albino rats were divided into three groups and received PEG, sodium phosphate or tap water alone (control). After 8 h, histological changes in colonic mucosa were evaluated. The tissue concentration of malonyldialdehyde (MDA), superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) in colon homogenates was also measured. Animals in the sodium phosphate and PEG groups had significantly more colonic mucosal damage than controls, the damage induced by sodium phosphate being worse than that caused by PEG. MDA levels were significantly higher in the sodium phosphate and PEG groups than in controls and were higher in the sodium phosphate group than in the PEG group, whereas differences in SOD and GSH-Px activities were significant only between control and both sodium phosphate and PEG groups. Sodium phosphate and PEG cause histological damage and trigger oxidative stress on colonic mucosa. The tissue damage and oxidative stress induced by sodium phosphate is more profound than that produced by PEG.

Network formation in polyethyleneglycol solutions. An intradiffusion study

Intradiffusion coefficients of binary mixtures, water–polyethyleneglycol (PEG) (molecular weight 200, 400, 2000, 3400, 10000 Da), were measured by pulsed gradient spin echo (PGSE)-NMR to determine the mass and concentration effects. The properties of polydisperse samples are compared with those of oligomers, and the effect of polydispersity is discussed. The PEG diffusion coefficients approach a constant value at high concentration, indicating the formation of a dynamic network between water and PEG molecules. The stochiometry of this network is evaluated and compared with the result of a model derived from an extension of gelation theory. It was found that at infinite dilution limiting self and mutual diffusion coefficients are not equal: this has been interpreted as an effect of polydispersity.

Effect of adsorption on the viscosity of dilute polymer solution

Measurements of the dilute solution viscosities of polyethylene glycol and polyvinyl alcohol in water were carried out. The reduced viscosities of both polymer solutions show an upward turning of curvature at the extremely dilute concentration region and this is similar to the phenomena observed for many polymer solutions in the early 1950s. Upon the changes of the flow time of pure water and the wall surface wettability of the viscometer after measuring solution viscosity, a judgement was formed that the observed viscosity abnormality at the extremely dilute concentration region is solely due to the effect of adsorption of polymer chains on the viscometer wall surface. A theory of the adsorption effect based on the Langmuir isotherms was proposed and a mathematical analysis for data treatment was performed. The theory could adequately describe the existing viscosity data. It seems necessary to correct the viscosity of a dilute polymer solution measured by a glass capillary viscometer for effect of adsorption in all cases.

Lamellar biogels comprising fluid membranes with a newly synthesized class of polyethylene glycol-surfactants

A series of four polymer–surfactant macromolecules, each consisting of a double-chain hydrophobic moiety attached onto a monofunctional polyethylene glycol (PEG) polymer chain, were synthesized in order to study their effect upon the fluid lamellar liquid crystalline (Lα) phase of the dimyristoylphosphatidylcholine/pentanol/water system. The main finding of this study is that the addition of these compounds induces a new lamellar gel, called Lα,g. We have determined the phase diagrams as a function of PEG–surfactant concentration, cPEG, and weight fraction water, ΦW. All phase diagrams are qualitatively similar and show the existence of the gel. Unlike more common polymer physical gels, this gel can be induced either by increasing cPEG or by adding water at constant cPEG. In particular, less polymer is required for gelation as water concentration increases. Moreover, the gel phase is attained at concentrations of PEG–surfactant far below that required for classical polymer gels and is stable at temperatures comparable to the lower critical solution temperature of free PEG–water mixtures. Small angle x-ray experiments demonstrate the lamellar structure of the gel phase, while wide angle x-ray scattering experiments prove that the structure is Lα, not Lβ′ (a common chain-ordered phase which is also a gel). The rheological behavior of the Lα,g phase demonstrates the existence of three dimensional elastic properties. Polarized light microscopy of Lα,g samples reveals that the Lα,g is induced by a proliferation of defect structures, including whispy lines, spherulitic defects, and a nematiclike Schlieren texture. We propose a model of topological defects created by the aggregation of PEG–surfactant into highly curved regions within the membranes. This model accounts for both the inverse relationship between ΦW and cPEG observed along the gel transition line and the scaling dependence of the interlayer spacing at the gel transition with the PEG molecular weight. These Lα hydrogels could serve as the matrix for membrane-anchored peptides, proteins or other drug molecules, creating a “bioactive gel” with mechanical stability deriving from the polymer–lipid minority component.

Determination of polyethylene glycols in water by reversed-phase high-performance liquid chromatography

This paper describes an RP-HPLC method to characterize the ozonation products of polyethylene glycols (PEGs) (general formula HO(CH 2CH 2O) n -H) with original mass 5000. Samples with different pH and ozonation times were studied. The amounts of individual products up to n = 56, the percentage of PEGs as a final product and the molecular distribution ( M w/ M n) were calculated. The samples were concentrated by liquid-liquid extraction.

Effect of a Liquid–Liquid Phase Separation on the Slopes of Density vs. Concentration Plots

Abstract The densities were measured for dextran (Dex)–polyethylene glycol (PEG)–water, poly(1-vinyl-2-pyrrolidone (PVP)–PEG–water, and poly(vinyl alcohol) (PVA)–PEG–water systems. In all cases, the linear relationship of the density vs. concentration plots was not affected by the occurrence of liquid–liquid phase separation. The partial specific volumes were calculated from the slopes of the straight lines of the density.

Separation of outer cysts from metacercariae of Fasciola gigantica in an aqueous two-phase system.

The outer cysts (Oc) of Fasciola gigantica metacercariae (Mc) were separated in an aqueous two-phase system composed of polyethylene glycol and dextran in distilled water. A large number of separated Mc without Oc were recovered in the bottom layer rich in dextran in the system. Ten separated Mc in the layer were used to inoculate the mouse with a syringe and juveniles were recovered from the animals on the 14th day. When the number of juveniles recovered was compared with that from the mice infected orally with the same number of Mc, there was a significant difference between them (P < 0.05). The former method is easier than the latter for inoculation.

Representation of binodal curves for aqueous polymer solutions using a new local composition model

A new local composition model is used to reproduce the phase separation phenomena of aqueous polymer solutions. The energy parameters can be expressed by a quadratic function of temperature. Solutions of polyethylene glycol or polypropylene glycol in water are studied. The phase equilibria of these binary solutions are represented with sufficient accuracy.

Theory of solvation-induced reentrant phase separation in polymer solutions.

A simple model of solvation is introduced to describe lower critical solution points in polymer solutions. Our theory predicts that physical bond formation between polymer segments and solvents can be a major cause of miscibility gaps showing a closed-loop or hourglass shape. Relative positions of upper and lower critical solution points are examined for the various molecular weights of the polymer. The result is compared with the observed phase diagram of polyethylene glycol in water.

EFFECT OF DRAG REDUCING POLYMER ADDITIVES ON FLOW THROUGH COMMERCIAL BENDS AND TEES.

Experimental studies of the total loss coefficient and pressure distribution, for turbulent Newtonian and drag reduction flows in bends and tees are presented. Dilute solutions of polyethylene glycol in water were used as the drag reducing fluids. Drag reduction was deduced from plots of experimental pipe flow data, on Prandtl-Karman coordinates. Two main test sections were studied. The first test section was a commercial 90° bend,while the second was a commercial tee section. The later test section was studied in different situations such as a distributer , a collector, a by-pass and a bend. Estimation of the total loss coefficient required an evaluation of a kinetic energy correction factor. Based on previous theoretical and experimental verifica-tions, this factor was determined from the friction factor Reynolds number pipe flow data, for the different flowing fluids. Thus, a reasonally accurate evaluation of the total loss coeffi-cient could be obtained. The results showed that drag reducing polymer additives cause a reduction in the total loss coefficient for all flow situations studied. Pressure distributions along the different sections were presented both with physical inter-pretations and discussion of some flow separation aspects. The results showed that the pressure distributions along the studied sections had the same trend for both Newtonian and drag reduction flows.

A thermoanalytic method for the study of the solubility of polyethylene glycols in ethanol and water

A simultaneous TG-DSC method has been used for the determination of the solubility of polyethylene glycols in ethanol-water solutions. As a comparison precipitation was studied in test tubes at cooling to 15 or 20°C as well as dissolution at heating to temperatures between 25 and 60°C. The results are shown in ternary diagrams for polyethylene glycols with molecular weights from 1500 to 35000.

Inclusion properties of freeze-thaw polyvinyl alcohol hydrogel.

A solution of a mixture of polyvinyl alcohol (PVA) and polyethylene glycol (PEG) in water gave a PVA hydrogel including PEG by a given cycle of freezing and thawing. The rate of the release of PEG from the gel decreased with increasing the molecular weight of PEG and the freezing cycle number. Diffusion coefficients of PEG in the gel were determined by the relationship between the release amounts and square root of release time. Diffusion coefficient decreased with increasing the cycle number, then becoming horizontal after a definite number of cycle which depended on the molecular weight of PEG. We found that emulsified triolein was also included in the gel by the freezing and thawing method.