Aqueous Solutions Of Polyethylene Glycol Research Articles

Prediction of gas solubility in binary polymer+solvent mixtures

This paper is devoted to a theory of gas solubility in highly asymmetrical mixed solvents composed of a low molecular weight (such as water, alcohol, etc.) and a high molecular weight (such as polymer, protein, etc.) cosolvents. The experimental solubilities of Ar, CH 4, C 2H 6 and C 3H 8 in aqueous solutions of polypropylene glycol and polyethylene glycol were selected for comparison with the theory. The approach for predicting these solubilities is based on the Kirkwood–Buff formalism for ternary mixtures, which allowed one to derive a rigorous expression for the Henry constant in mixed solvents. Starting from this expression, the solubilities could be predicted in terms of those in each of the two constituents and the properties of the mixed solvent. This expression combined with the Flory–Huggins equation for the activity coefficient in a binary mixed solvent provided very accurate results, when the Flory–Huggins interaction parameter was used as an adjustable quantity. A simple expression in which the solubility could be predicted in terms of those in each of the two constituents and the molar volumes of the latter was also derived. While less accurate that the previous expression, it provided more than satisfactory results.

Morphological study of fluorinated asymmetric polyetherimide ultrafiltration membranes by surface modifying macromolecules

Phase inversion polyetherimide (PEI) flat sheet membranes were surface modified using fluorinated surface modifying macromolecules (SMMs) additives. Two SMM formulations were used. Each SMM was blended into polyetherimide casting solutions containing the solvent N, N-dimethyleacetamide and the non-solvent hydroxybutyric acid γ-lactone (GBL). The effects of the SMM and the PEI base polymer concentrations on the morphological properties of the prepared membranes have been investigated. Contact angle measurements indicate that PEI membrane surface becomes more hydrophobic after adding the SMMs to the PEI casting solutions, while X-ray photoelectron spectroscopy analysis shows enrichment of fluorine on the PEI membrane surfaces. The SMM modified and unmodified PEI membranes were also characterized by means of atomic force microscopy (AFM), gas permeation tests and ultrafiltration experiments using aqueous solutions of polyethylene glycol (PEG) and polyethylene oxide (PEO) of various molecular weights. Pore sizes and nodule sizes obtained from AFM images were remarkably fitted to the log-normal probability distribution curves. Mean pore sizes, pore size distributions, nodule sizes, nodule size distributions and roughness parameters of the membranes were determined. It was found that SMM actively migrated to the air surface and changed the surface properties of the PEI membranes. The mean pore size and the molecular weight cut-off (MWCO) of the SMM modified PEI membranes were lower than those corresponding to the unmodified membranes, while the nodule sizes were larger. The surface roughness parameters were reduced when SMMs were added.

The effect of electrolytes on the cloud point of poly ethylene glycol aqueous solutions

Cloud points of aqueous solutions of poly ethylene glycol (PEG)/inorganic salts are measured using the particle counting method. The average molecular weights of PEG are 3,350 and 10,000. NaH2PO4, Na2HPO4, KH2PO4 and K2HPO4 are the inorganic salts used. Measurements are done for different weight percentage of PEG and salts in water.

Changes in cisplatin delivery due to surface-coated poly (lactic acid)-poly(epsilon-caprolactone) microspheres.

Smooth muscle cell proliferation plays a major role in the genesis of restenosis after angioplasty or vascular injury. Local delivery of agents capable of modulating vascular responses, have the potential to prevent restenosis. However, the development of injectable microspheres for sustained drug delivery to the arterial wall is a major challenge. We demonstrated the possibility of entrapping an antiproliferative agent, cisplatin, in a series of surface coated biodegradable microspheres composed of poly(lactic acid)poly(caprolactone) blends, with a mean diameter of 2-10 pm. The microspheres were surface coated with poly ethylene glycol (PEG), chitosan (Chit), or alginate (Alg). A solution of cisplatin and a 50:50 blend of polylactic acid (PLA)-polycaprolactone (PCL) dissolved in acetone-dichloromethane mixture was poured into an aqueous solution of PEG (or polyvinyl alcohol or Chit or Alg) with stirring using a high speed homogenizer, for the formation of microspheres. Cisplatin recovery in microspheres ranged from 25-45% depending on the emulsification system used for the preparations. Scanning electron microscopy revealed that the PLA-PCL microspheres were spherical in shape and had a smooth surface texture. The amount of drug release was much higher initially (20-30%), this was followed by a constant slow-release profile for a 30-day period of study. It has been found that drug release depends on the amount of entrapped drug, on the presence of extra cisplatin in the dispensing phase, and on the polymer coatings. This PEG or Alg-coated PLA/PCL microsphere formulation may have potential for the targeted delivery of antiproliferative agents to treat restenosis.

Heat Transfer Coefficient Prediction for Falling Film Evaporation Used for Solvent Removal from Highly Viscous Liquids

The paper deals with the mixture effect correction for falling film evaporation of solutions containing dissolved solids. It is shown that the correction arises from vapour-liquid equilibrium effects similar to those observed for boiling of multi-component liquid mixtures. The predictive method reported here uses the HTFS correlation 1 to obtain the heat transfer coefficient for the highly viscous equivalent pure fluid, and then applies a mixture effect correction to it. Data for falling film evaporation from aqueous solutions of polyethylene glycol are predicted reasonably well by the method.

Vapor Pressure Osmometry and Its Applications in the Osmotic Coefficients Determination of the Aqueous Monomer Glycol and Polymer Polyethylene Glycol Solutions at Various Temperature

AbstractBased on the principle and calibration of vapor pressure osmometer and its application in the thermodynamics of the aqueous solutions, the results on aqueous solutions of monomer glycol, PEG200, PEG400, PEG1500 and PEG2000, over the different concentration range at various temperatures were reported. Using a linear least‐square fitting routing, the osmotic coefficients were fitted by a simple polynomial equation. It was found that the relationship between the molar osmotic coefficients (ϕ) and the molar concentration (c) of the solutions are in a quite good agreement with the fitted polynomial equation at various temperatures over the different concentration range. The experimental results also show that over the studied concentration range and at various temperatures, the concentration dependence of the molar osmotic coefficients of the aqueous solution systems with the solutes of PEG200, PEG400, PEG1500 and PEG2000 are totally presented in a rising trend, and their temperature dependence of the osmotic coefficients of the aqueous solution systems of the molar concentration exhibits their own regularities, respectively. The aqueous glycol solution system exhibits the properties of the dilute solution.

Effect of polymer and temperature on the critical micellar concentration of aqueous sodium dodecyl sulfate

The critical micellar concentrations (cmc) of SDS in aqueous polyethylene glycol (M.W. 35000) solutions have been determined at different temperatures. The cmc of SDS increases with the increase in concentration of PEG and decreases with increase of temperature. The critical aggregation concentration (CAC) and polymer saturation point (PSP) decrease with increase in temperature. The effect of the increase in polymer concentration of CAC and PSP has been determined. The thermodynamic quantities associated with the PSP are computed. Intrinsic viscosity [η] of the PEG increases with increase in SDS concentration.

A new module arrangement for plasmapheresis

On-line plasmapheresis using microporous membranes for filtration normally requires two external circulations (double treatment) before the detoxified plasma can be returned to the patient. The duomodule, a new filter arrangement developed by our group, integrates both steps in one equipment module using only one external circuit. Separations of aqueous polyethylene glycol (PEG) solutions as well as human plasma were carried out using the duomodule arrangement. The results revealed a considerable decrease of higher molecular substances in the feed solutions and a significant increase of these components in the permeate solution accumulated in the external compartment of the module. In conclusion, the duomodule arrangement seems to be an useful tool for the therapeutic apheresis.

Measurement of solution viscosity by atomic force microscopy

We report on studies aimed at employing the atomic force microscope (AFM) to measure the viscosity of aqueous solutions. At ambient temperature, the AFM cantilever undergoes thermal fluctuations that are highly sensitive to the local environment. Here, we present measurements of the cantilever’s resonant frequency in aqueous solutions of glycerol, sucrose, ethanol, sodium chloride, polyethylene glycol, and bovine plasma albumin. The measurements revealed that variations in the resonant frequency of the cantilever in the different solutions are largely dependent on the viscosity of the medium. An application of this technique is to monitor the progression of a chemical reaction where a change in viscosity is expected to occur. An example is demonstrated through monitoring of the hydrolysis of double stranded deoxyribonucleic acid by DNase I.

Ultrasonic Velocity and Absorption Measurements for Polyethylene glycol and Water Solutions

Ultrasonic velocity at 3 MHz using the pulse echo overlap method over the temperature range of 10–90°C and absorption coefficient over the frequency range of 0.2–2 MHz using the plano-concave resonator method at 30°C were measured in an aqueous solution of polyethylene glycol over the concentration range of 5% to 25% by weight. The velocity exhibited a maximum value at approximately 30°C, 40°C, 50°C, 60°C and 70°C in 25%, 20%, 15%, 10%, and 5% solutions, respectively. The velocity increased with concentration at a given temperature. The ultrasonic relaxation in polyethylene glycol aqueous solutions, which may be the result of structural fluctuations of polymer molecules such as the internal motion of the polymer chains, was observed, and the change of α/f2 was greater at lower frequencies, especially below 0.5 MHz. The shear viscosity decreased with temperature and increased with concentration.

Physical solubility of hydrogen sulfide in several aqueous solvents

AbstractThe solubility of hydrogen sulfide in several aqueous solutions was measured over the temperature range 25°C to 60°C. The solvents investigated in this work include 0 to 50% aqueous solutions of polyethylene glycol, ethylene glycol, methyldiethanolamine and diethanolamine. The amine solutions used in this work were neutralized by the addition of hydrochloric acid in order to suppress the hydrogen sulfide reaction (H2S → H+ + HS−) so that only the physical solubility of hydrogen sulfide would be measured. The solubility data determined in this work are expressed in terms of Henry's law. The Henry's law constants found in this work were correlated well by a particularly simple empirical formula based on the molecular weight of the solvent.

Colchicine Encapsulation within Poly(Ethylene Glycol)-Coated Poly(Lactic Acid)/Poly(?-Caprolactone) Microspheres-Controlled Release Studies

Smooth muscle cell proliferation plays a major role in the genesis of restenosis after angioplasty or vascular injury. Local delivery of agents capable of modulating vascular responses have the potential to prevent restenosis. However, the development of injectable microspheres for maintaining high tissue levels of drugs at the site of vascular injury is a major challenge. We demonstrated the possibility of entrapping an antiproliferative agent, colchicine, in polyethylene glycol (PEG)-coated biodegradable microspheres composed of poly(lactic acid)/poly(epsilon-caprolactone) blends, with a mean diameter of 3-6 microm. A solution of colchicine and blends of polylactic acid (PLA)/polycaprolactone (PCL) dissolved in acetone-dichloromethane mixture was poured into an aqueous solution of PEG (or polyvinyl alcohol) with stirring by a high-speed homogenizer to form microspheres. Colchicine recovery in microspheres ranged from 30-50% depending on the emulsification system and the ratio of polymer blends used for the preparations. Scanning electron microscopy revealed that the PLA/PCL microspheres were spherical in shape and had a smooth surface texture. Results of in vitro release studies showed that it is possible to control the colchicine release by choosing the appropriate particle size, loading, and PLA/PCL composition. Water permeability through the PLA membrane was greater, when compared with PCL blends. The amount of drug release also was much higher (58.3%) in PLA compared with PCL (39.3%) microspheres, for 30 days. Therefore, we concluded that the drug release from the microspheres followed a diffusion mechanism where bulk erosion and surface deposition were negligible. These PEG-coated PLA/PCL microspheres may have potential for targeting antiproliferative agents for prolonged periods to treat restenosis.

Benzotriazole as inhibitor for copper with and without corrosion products in aqueous polyethylene glycol

Electrochemical methods, including polarization experiments and impedance spectroscopy, were used to evaluate the eAectiveness of benzotriazole (BTA) in an aqueous solution of polyethylene glycol (PEG) in protecting polished archaeological copper or archaeological copper covered with corrosion products. The adsorption of PEG on the polished copper significantly limited the corrosion current. The presence of benzotriazole enhanced the protection of the polished copper, giving maximum protection at a concentration of 10 ˇ2 mol l ˇ1 of BTA in 20 vol % PEG 400 solution. On the other hand, PEG solutions caused degradation of the corrosion products of the copper. This degradation increased with time. When BTA was added, the corrosion products were preserved and, the higher the BTA concentration, the more the corrosion current decreased. In PEG 400 solution protection of the corrosion products of the copper by BTA improved over time.

Study on heat transport rate of an osmotic heat pipe: III. Estimation of heat transport limits

This paper describes an experimental and theoretical study on the heat transport limits of an osmotic heat pipe operated under atmospheric pressure, using an aqueous solution of polyethylene glycol 600 (0.1 to 1.0 kmol/m 3 ) as the working fluid and 18 tubular-type acetyl cellulose osmotic membranes. The correlation between the heat transport rate and the effective osmotic area is clarified. Also, the effects of the physical properties of the solution and the geometry of the osmotic heat pipe (e.g., inside diameters of flow lines) on the heat transport rate are theoretically examined. The heat transport rate of the present osmotic heat pipe is found to be about 85% compared with that under an ideal condition such that the solution circulation flow rate is very large, that is, the average concentration in a membrane module is equal to that in the solution loop.

The wall effect on viscosity measurement of dilute aqueous solutions of polyethylene glycol and polyvinyl alcohol using a paraffin-coated capillary viscometer

The relative viscosities of aqueous solutions of a polyethylene glycol sample and a polyvinyl alcohol sample were measured in a viscometer, the capillary wall surface of which was coated with paraffin. The results were compared with the data obtained from the original non-coated viscometer. Slippage occurs in the former case due to the hydrophobic nature of paraffin, while in the latter case, conventional viscous flow operates since both the solvent water and solution either wet and/or are adsorbed on to the glass capillary surface of the viscometer. The experimental data were analyzed with the aid of the recently proposed theory of the effect of solute adsorption on relative viscosity measurements. The formula, accounting for the effect of solute adsorption of polymer solutions down to the extremely dilute concentration region, are also applicable to non-wetting polymer solutions in which solute adsorption is eliminated. The results obtained were compared and analyzed using the idea of extrapolation length of slip flow proposed by de Gennes PG. CR Acad Sci Paris 1979;288B:219. The extrapolation length could be evaluated unambiguously from the relative or reduced viscosity data for polymer solutions down to the extremely dilute concentration region.

Part 1. Direct Measurement of Depletion Attraction and Thin Film Viscosity between Lipid Bilayers in Aqueous Polyethylene Glycol Solutions

Using the surface forces apparatus, we have measured the static and hydrodynamic forces between two substrate supported lipid bilayers in water and semidilute aqueous solutions of 8000 MW poly(ethylene glycol) (PEG), a neutral polymer for which water is a good solvent. At small separations (D < RF, Flory radius), an enhanced adhesion due to depletion attraction was measured. Conversely, at larger separations we found a repulsive barrier, which is not predicted by mean-field theories. Dynamic measurements of the viscosity as a function of film thickness reflected the same pattern of behavior as exhibited in the static force experiments: Thus, in the absence of polymer, the shear plane was at the lipid-water interface, while in the 8000 MW polymer solution the viscosity decreased as a function of decreasing surface separation due to a polymer-depleted layer of lower viscosity at the bilayer surface. We discuss our results in terms of depletion attraction, depletion stabilization, thin film lubrication, the...

Ultrasonic behaviour of aqueous solutions of polyethylene glycols on the temperature of adiabatic compressibility minimum of water

The effect of Polyethylene Glycol-200 (PEG-200), Poly-ethylene Glycol-300 (PEG-300), Polyethylene Glycol-400 (PEG-400) and Polyethylene Glycol-600 (PEG-600) on the temperature corresponding to the adiabatic compressibility minimum (TACM) of water has been studied using the ultrasonic interferometer. Studies on the variation of adiabatic compressibility of aqueous solutions of nonelectrolytes at temperatures near the adiabatic compressibility minimum yield information regarding the structural propensities of the solutes in water. The present studies indicate that PEG-200,PEG-300, PEG-400 and PEG-600 act as water structure breakers throughout the concentration range studied and the structure breaking ability increases with an increase in polymeric chain length.

Role of Brij micelles in the quenching of fluorescence of Safranine T by inorganic ions

The results of quenching of fluorescence of the dye Safranine T (ST) by the inorganic ions [Fe(CN)6]3−, [Fe(CN)6]4−, Cu2+, Co2+, Ni2+ and Mn2+ in aqueous micellar solutions of the surfactants diethylene glycol hexadecyl ether (Brij 52), decaethylene glycol hexadecyl ether (Brij 56) and cicosaethylene glycol hexadecyl ether (Brij 58) are presented. The quenching results have been processed in the light of Stern-Volmer (SV) equation and its modified forms to evaluate the extents of interaction between the fluorophore (ST) and the quencher. The magnitudes of the Stern-Volmer constant (KSV) in quencher micelles follow the trend [Fe(CN)6]3− > [Fe(CN)6]4− > Co2+ > Cu2> Ni2+> Mn2+ in all the Brij media; for each ion the trend in terms of the surfactants is Brij 52> Brij 56> Brij 58, which is the order of the polarity of the Brij environment. The ion Co2+ appears to partly quench the emission process by the static mode. The solvent parameters of the Brij micellar media like the Kosower Z value, the transition energy for the intramolecular charge transfer, ET30 and the dielectric constant, D, have been estimated from the shift between the absorption and emission frequencies. A comparison of the quenching behaviours of inorganic ions on ST fluorescence in different media viz., aqueous, aqueous polyethylene glycol and aqueous micellar solutions of Tweens and Brijs has been presented.

Application of the thermodynamics of mobile order and disorder to explain the solubility of temazepam in aqueous solutions of polyethylene glycol 6000

The aqueous solubility of temazepam, a poorly water-soluble drug, markedly increased when polyethylene glycol (PEG) 6000 was added to the solvent. To a first approximation this enhancement is proportional to the weight fraction of the polymer, and at a concentration of 15% w/w of PEG 6000, the solubility increased by a factor of two at 24°C. Similar observations were made at 34 and 46°C. The linearity of the solubility effect was investigated using the new thermodynamics of the mobile order and disorder. It is hypothesized that random mixing is unlikely to occur, but instead, a segregation of the binary solvent in zones with a high or low polymer concentration is suggested.

Investigation of aqueous solutions by modulated temperature differential scanning calorimetry

The influence of variables on the observation of thermal events and on the determination of heats of transformation at freezing and thawing in aqueous solutions was investigated using modulated temperature differential scanning calorimetry (MTDSC, ODSC). The investigated systems were pure water and dilute aqueous solutions of polyethylene glycol (PEG) 6000. The influence of eleven combinations of frequency, amplitude and underlying heating rate was analyzed in heating–cooling scans. The selection of variables had a great impact on the shape of the c p component curve as well as on the amount of heat expressed by the c p component, Δ H c , of the thermal event. The conventional Δ H-values were not influenced to the same extent. The ratio Δ H c /Δ H of the melting process might be an expression of the degree of relative crystallinity in frozen aqueous solutions. The requirement of operational setting is an appropriate degree of oscillation in combination with a number of modulations over a distinct transformation temperature. The selection of variables must produce a heating–cooling scan.