Aqueous Solutions Of Polyethylene Glycol Research Articles

Formation of Spherical and Non‐Spherical Eutectic Gallium‐Indium Liquid‐Metal Microdroplets in Microfluidic Channels at Room Temperature

AbstractHere, the formation of eutectic Gallium‐Indium (EGaIn) liquid‐metal microdroplets, both spherical and non‐spherical, in microfluidic devices at room temperature is reported. Monodisperse microdroplets were created in an aqueous polyethylene glycol (PEG) solution, in oxygenated and in deoxygenated silicone oil. The volume of the droplets depends on the channel dimensions and flow rates applied, varying between 0.5 and 4 nL. Non‐spherical droplets were formed in oxygenated silicone oil due to the instantaneous formation of an oxide layer. These metal “micro‐rice” droplets retained their shape and did not spontaneously reflow to form shapes of the lowest interfacial energy on egress from the channel, unlike in aqueous PEG solution and in deoxygenated silicone oil. Liquid‐metal droplets with such tunable morphology can potentially be used in MEMS devices for optical and electrical switches, valves and micropumps.

Nanomechanical Properties of Polyethylene Glycol Brushes on Gold Substrates

A necessary step in advancing the use of polyethylene glycol (PEG) surface coatings in critical biotechnological applications such as cancer treatments is to provide direct and reliable nanoscale property characterization. Measurements for such characterization are currently provided by scanning probe methods, which are capable of assessing heterogeneity of both surface coverage and properties with nanoscale spatial resolution. In particular, atomic force microscopy (AFM) can be used to detect and quantify the heterogeneity of surface coverage, whereas atomic force spectroscopy can be used to determine mechanical properties, thereby revealing possible heterogeneity of properties within coatings. In this work, AFM and force spectroscopy were used to characterize the morphology and mechanical properties of thiol-functionalized PEG surface coatings on flat gold substrates in aqueous PEG solution. Thiol-functionalized PEG offers a direct and simple method of attachment to gold substrates without intermediate anchoring layers and therefore can be exploited in developing PEG-functionalized gold nanoparticles. AFM was used to investigate the morphology of the PEG coatings as a function of molecular weight; the commonly observed coverage was in the form of sparse, brushlike islands. Similarly, force spectroscopy was utilized to study the mechanical properties of the PEG coatings in compression and tension as a function of molecular weight. A constitutive description of the mechanical properties of PEG brushes was achieved through a combinatorial analysis of the statistical responses acquired in both compression and tension tests. Such a statistical characterization provides a straightforward procedure to assess the nanoscale heterogeneity in the morphology and properties of PEG coverage.

Concentration Dependence of the Interfacial Tension for Aqueous Two-Phase Polymer Solutions of Dextran and Polyethylene Glycol

We studied the interfacial tension between coexisting phases of aqueous solutions of dextran and polyethylene glycol. First, we characterized the phase diagram of the system and located the binodal. Second, the tie lines between the coexisting phases were determined using a method that only requires measuring the density of the coexisting phases. The interfacial tension was then measured by a spinning drop tensiometer over a broad range of polymer concentrations close to and above the critical point. In this range, the interfacial tension increases by 4 orders of magnitude with increasing polymer concentration. The scaling exponents of the interfacial tension, the correlation length, and order parameters were evaluated and showed a crossover behavior depending on the distance to the critical concentration. The scaling exponent of the interfacial tension attains the value 1.50 ± 0.01 further away from the critical point, in good agreement with mean field theory, but the increased value 1.67 ± 0.10 closer to this point, which disagrees with the Ising value 1.26. We discuss possible reasons for this discrepancy. The composition and density differences between the two coexisting phases, which may be taken as two possible order parameters, showed the expected crossover from mean field behavior to Ising model behavior as the critical point is approached. The crossover behavior of aqueous two-phase polymer solutions with increasing concentration is similar to that of polymer solutions undergoing phase separation induced by lowering the temperature.

Design and performance characterization of a new shear enhanced module with inbuilt cleaning arrangement

BACKGROUND: Shear enhanced membrane modules are becoming popular as they enable high permeate flux in almost all membrane filtration processes due to the high shear rate they generate at the membrane surface. In this article, the design of a new shear enhanced module with unique hydrodynamic cleaning facility is proposed. The device, presently at laboratory scale was named the Spinning Basket Membrane (SBM) module because of its inherent structural similarity with the well known Spinning Basket Reactor. An aqueous solution of polyethylene glycol was chosen as test fluid for the present study. RESULTS: The module was characterized under different parametric conditions of transmembrane pressure (TMP), feed concentration (C0) and rotational speed of the basket (Ω). It was observed that with its inbuilt cleaning facility the module was able to restrict the flux decline to within 15% of its start up value, even after 21 h of continuous running, with a maximum initial flux as high as 612 L m−2 h−1. CONCLUSION: Based on the performance of the module, it may be concluded that this module could be scaled up for nearly uninterrupted industrial operation with reduced requirement for chemical cleaning, which is rare in the membrane industry to date. Copyright © 2012 Society of Chemical Industry

Pressure Drop in Entrance Flows from Cavity to Slot of Viscoelastic Fluids inside Slot Die

In this work, entrance flows of viscoelastic fluids from a cavity to a slot in a slot die coating were investigated experimentally and numerically. Aqueous solutions of polyethylene glycol (PEG) and polyethylene oxide (PEO) mixtures, having viscoelasticity and Newtonian viscosity, were tested in order to clarify the effects of viscoelastic characteristics to the excess pressure drops at the entrance. The measured excess pressure drop changes corresponded to the flow pattern changes from a Newtonian-like flow pattern to vortex generation and growth patterns in an asymmetric entrance flow with a submillimeter slot. Numerical predictions of the transitions in the flow patterns and the pressure drops were also made utilizing exponential Phan-Thien-Tanner (EPTT) model with a finite element method. The predictions qualitatively indicated the increase in excess pressure drop and the vortex generation and growth.

Preparation of bioactive interferon alpha– loaded polysaccharide nanoparticles using a new approach of temperature-induced water phase/water-phase emulsion

The aim of this study was to develop a temperature-induced polyethylene glycol (PEG) water phase/polysaccharide water-phase emulsion approach for preparing interferon alpha-2b (IFNα-2b)-loaded polysaccharide nanoparticles. IFNα-2b was first added to a mixture of an aqueous solution of PEG and polysaccharide. The mixture solution was stirred in a magnetic stirrer at a rate of 2000 rpm for 45 seconds at 0°C ± 0.5°C. The solution was then prefrozen at different temperatures. The polysaccharide and IFNα-2b partitioned in the polysaccharide phase were preferentially separated out as the dispersed phase from the mixture solution during the prefreezing process. Then the prefrozen sample was freeze-dried to powder form. In order to remove the PEG, the powder was washed with dichloromethane. Once IFNα-2b was loaded into the polysaccharide nanoparticles, these nanoparticles could gain resistance to vapor–water and water–oil interfaces to protect IFNα-2b. The antiviral activity of the polysaccharide nanoparticles in vitro was highly preserved (above 97%), while the antiviral activity of IFNα-2b–loaded polysaccharide nanoparticles using the control water-in-oil-in-water method was only 71%. The antiviral activity of the IFNα-2b from blood samples was also determined on the basis of the activity to inhibit the cytopathic effects of the Sindbis virus on Follicular Lymphoma cells (FL). The antiviral activity in vivo was also highly preserved (above 97%). These polysaccharide nanoparticles could be processed to different formulations according to clinical requirements.

Mixed Micellization Behavior of m‐2‐m Gemini Surfactants with Some Conventional Surfactants at Different Temperatures

AbstractMixed micellization behavior of dimeric cationic surfactants ethanediyl‐1,2‐bis(dimethyl alkyl ammonium bromide) (m‐2‐m where m = 10, 12) with conventional single chain cationic surfactants like cetyltrimethyl ammonium bromide (CTAB), cetylpyridinium chloride (CPC), tetradecyl dimethyl benzyl ammonium chloride (C14BCl) and cetyl dimethyl benzyl ammonium chloride (C16BCl) were studied in aqueous and aqueous polyethylene glycol (PEG) solutions at 298.15, 308.15 and 318.15 K respectively using conductometric and viscometric methods. In aqueous solutions, all the combinations (except 12‐2‐12 + CTAB) were found to behave nonideally with mutual synergism which decreases with increase in temperature. Various thermodynamic parameters of micellization like , and were evaluated and discussed. Similarly in presence of PEG, the thermodynamic properties like , and associated with the transfer of surfactant monomers from the medium consisting of polymer‐free mixed micelles to polymer‐bound mixed micelles at various temperatures were also calculated. The negative values of show that aggregation process is more exothermic than micellization whereas the negative values of indicate that the presence of polymer bound mixed micelles decreases the degree of randomness of the system. Viscosity studies show that in aqueous solutions all the combinations of 10‐2‐10/12‐2‐12 display negative departure in the relative viscosity (ηr) from additivity rule which decreases with increase in temperature. Similarly in the presence of 5% PEG solutions the magnitude of the negative departure decreases for all the combinations and becomes positive in the case of C14BCl and CPC combinations with the studied gemini surfactants at higher temperatures.

Sonography of the small bowel after oral administration of fluid: an assessment of the diagnostic value of the technique

This study was performed to assess the feasibility and possible advantages of bowel sonography after fluid filling of intestinal loops compared with conventional sonography. Forty-five consecutive patients with known or suspected coeliac disease (35 females, ten males; age range 11-65 years) prospectively underwent sonography before and after ingestion of 750 ml of an aqueous solution of polyethylene glycol. Results before and after fluid distension were compared to assess whether luminal filling improved small-bowel visualisation. Luminal filling improved visualisation of intestinal features (luminal diameter, mucosal folds, parietal layers) in 77.6% of cases (marked, moderate or mild improvement in 2, 16 and 17 patients; 4.4%, 35.5% and 37.7%), respectively, and showed no change or worsening in 20% and 2.2% nine and one patient), respectively. Baseline examination showed abnormal features in 13/25 celiac patients (dilated fluid-filled loops, increased peristalsis, transient intussusception, mesenteric lymph nodes, intraperitoneal fluid). Reexamination after luminal filling showed additional abnormalities in six of the previous 13 and in three further coeliac patients. There were no false positive signs due to fluid administration. Luminal filling can improve visualisation of bowel walls and fold pattern and may be helpful in selected cases.

Effect of water-soluble polymers, polyethylene glycol and poly(vinylpyrrolidone), on the gelation of aqueous micellar solutions of Pluronic copolymer F127

The micellization of F127 (E98P67E98) in dilute aqueous solutions of polyethylene glycol (PEG6000 and PEG35000) and poly(vinylpyrrolidone) (PVP K30 and PVP K90) is studied. The average hydrodynamic radius (rh,app) obtained from the dynamic light scattering technique increased with increase in PEG concentration but decreased on addition of PVP, results which are consistent with interaction of the micelles with PEG and the formation of micelles clusters, but no such interaction occurs with PVP. Tube inversion was used to determine the onset of gelation. The critical concentration of F127 for gelation increased on addition of PEG and of PVP K30 but decreased on addition of PVP K90. Small-angle X-ray scattering (SAXS) was used to show that the 30wt% F127 gel structure (fcc) was independent of polymer type and concentration, as was the d-spacing and so the micelle hard-sphere radius. The maximum elastic modulus (Gmax′) of 30wt% F127 decreased from its value for water alone as PEG was added, but was little changed by adding PVP. These results are consistent with the packed-micelles in the 30wt% F127 gel being effectively isolated from the polymer solution on the microscale while, especially for the PEG, being mixed on the macroscale.

Analysis of an ultrafiltration model: Influence of operational conditions

Ultrafiltration is a widely used technique to remove hazardous pollutants from wastewaters. As ultrafiltration is a dynamic process, non steady-state UF models have been widely investigated and described in the literature. The main equations of most dynamic models found in the literature can be rearranged and simplified into a linear equation. In this work, experimental results from UF tests were expressed in terms of TMP 2 /J P 2 as a function of time to check linearity. Transmembrane pressure (TMP), feed concentration (FC), temperature and crossflow velocity (CFV) were varied during the experiments. The feed consisted in an aqueous solution of polyethylene glycol of 35 kg/mol molecular weight. The experimental results confirmed a linear relationship when TMP 2 /J P 2 was plotted vs. time. For severe fouling conditions, the linearity found when plotting experimental values of initial membrane fouling resistance vs. TMP was very high. A linear correlation between the initial membrane fouling resistance and the temperature was also found for the experimental conditions tested. However, it was found that, above 25 °C, increasing temperature did not result in a noticeable reduction of the gel layer resistance. The quotient r c /c g as a function of TMP and CFV was also evaluated to check if it followed any pattern.

Extraction of gold(III) from chloride media in aqueous polyethylene glycol-based two-phase system

Experimental results obtained for gold(III) extraction in aqueous polyethylene glycol (PEG)-based two-phase system using chloride ions as extracting agents are presented in this study. The experiments were performed by batch technique, using an aqueous two-phase system prepared by mixing equal volumes of 40% (w/w) PEG(1500) aqueous solution and 40% (w/w) (NH 4) 2SO 4 aqueous solution, both in absence and in presence of chloride ions extractants. The influence of several experimental parameters, such as initial gold(III) concentration, salt stock solution pH and chloride ions extractant concentration on gold(III) extraction efficiency was investigated. The experimental results have shown that gold(III) is quantitatively extracted (>98%) into PEG-rich phase in acid media (pH ⩽ 3.0) and at chloride ions concentration higher than 0.08 mol L −1. From the distribution coefficients determined as a function of chloride ions concentration into PEG-rich phase, the extracted species were identified. The comparison of the extraction behaviours of gold(III) and other metal ions (Cu(II), Co(II), Ni(II), Zn(II), Fe(III) and Pb(II)) was also examined. The validation of this method was done by recovery of gold from electrical wastes. The results present in this study show that the aqueous polyethylene glycol-based two-phase extraction system has potential for practical application in the extraction and separation of gold from chloride media.

The solubility of 17 beta-oestradiol in aqueous polyethylene glycol 400.

The solubility of 17 beta-oestradiol (E2) in aqueous solutions of polyethylene glycol (PEG) 400 has been measured at 35 degrees C. Up to 80% w/w PEG the solubility data conform to a log linear equation ln S = ln Sw + f sigma where S is the E2 concentration in the water/cosolvent mixture, Sw is E2 solubility in water, f is the weight fraction of PEG 400 and sigma is a parameter representing the solubilizing power of the cosolvent for the drug. Above 80% PEG the relationship becomes less convincing, with significant deviation from anticipated values. Reasons for these aberrations are discussed. It is suggested that conformational changes may be induced in the PEG by the addition of small quantities of water. Deviations noted for the melting point, viscosity and density data of PEG 400-water solutions may also confirm this suggestion.

Membranes of epitaxial-like packed, super aligned electrospun micron hollow poly(l-lactic acid) (PLLA) fibers

Novel epitaxial-like packed, super aligned, mono-layered hollow fibrous membranes were prepared by co-axial electrospinning technology. PLLA pellets were dissolved in solvent mixture of dichloromethane and dimethyl formamide (DCM/DMF=9:1) to prepare sheath solution dope with various concentrations (from 8 to 19wt.%). Aqueous solution of poly-ethylene glycol (PEG) was used as core solution dope. During the electrospinning process, dope concentrations and feed rate ratios were adjusted, separately, to evaluate the formation of resulting membranes. With lower shell solution concentration (from 8 to 15wt.%), the collected, flattened film showed arrangement of lower order. A stood-up film was clearly seen when concentration increased to 17wt.% and higher. As the collecting time went longer, these fibers piled up and eventually, stood up as a thin film from the surface of collector. Increasing flow rate ratio (FRR) also resulted similar outcomes and verify the cause of this phenomenon. After washing with water, scanning electron microscopy (SEM) revealed sheets of mono-layered, micron-sized hollow fiber arrays which were well aligned and tightly packed, just like the epitaxial growth of some semiconducting materials. These perfectly aligned and tightly packed hollow fiber arrays can be considered as highly anisotropic scaffolds that mimic tissue structures, such as nerve tissue, vascular structure as well as other application.

The inverse problem in granulation modeling—Two different statistical approaches

AbstractThis article is concerned with parameter estimation for a multidimensional population balance model for granulation. Experimental results were obtained by running a laboratory mixer with sodium carbonate and aqueous polyethylene glycol solutions. Subsequently, a prescan of suitable parameter combinations utilising the experimental results is performed, and a local surrogate model constructed around the best combination. For the actual estimation of the parameters and their uncertainties two different approaches are applied—a projection method and a Bayesian approach. It is found that the model predictions with the parameters obtained through both methods are similar. Furthermore, the uncertainties in the model predictions increase as the experimental uncertainties are increased. Studies of the marginal densities of two‐parameter combinations obtained through the Bayesian approach show a correlation between the collision and breakage rate constant, giving potential hints for further model development. Furthermore, a bimodal distribution of the compaction rate constant is observed. © 2011 American Institute of Chemical Engineers AIChE J, 2011

Rheological properties of aqueous solutions of polyethylene glycols with various molecular weights

The dependences of the kinematic viscosity of dilute aqueous solutions of polyethylene glycols (PEGs) with various molecular weights in the temperature range of 293.15–323.15 K were investigated. The intrinsic viscosity, the Huggins constant, and the activation energy of a viscous flow were calculated for these solutions. Proposals regarding the structure of polymer macromolecules in solution are made. The constants of the Mark-Kuhn-Hauvink equation required to estimate the polymer molecular weights were determined for PEG-water systems at various temperatures.

Extraction–thermal lens quantification of cobalt with Nitroso-R-Salt in two-phase aqueous systems with water-soluble polymer polyethylene glycol

A novel method is proposed for the extraction-thermal lens quantification of cobalt with Nitroso-R-Salt based on the distribution of the colored complex in a two-phase aqueous system on the basis of poly-ethylene glycol (PEG) and an ammonium sulfate solution followed by its thermal lens detection in the extract. The limit of detection is 0.3 μM (20 ng/mL); the lower limit of the analytical range is 0.7 μM (40 ng/mL); the relative standard deviation for the concentrations 1–50 μM makes 1–3% (n = 6, P = 0.95). In the determination of cobalt by spectrophotometry under the same conditions, the detection limit is 10 μM (0.6 μg/mL) and the lower limit of the analytical range is 40 μM (2.5 μg/mL). The precision of thermal lens measurements in PEG solutions is higher in comparison to that in aqueous ones because of the weaker interference of convection in aqueous solutions of PEG.

Relaxation dynamics and evidence of scaling behaviours in aqueous polymer solutions

Some Brillouin scattering experiments on aqueous solution of Polyethylene glycol and Polyethylene glycol dimethyl ether are presented. In all the systems non-Debye relaxation processes have been detected, occurring on the picosecond time scale. The average values of the relaxation time distributions fail to follow simple Arrhenius behaviours. The temperature evolution of the relaxation time is adequately fitted after the adoption of a phenomenological Vogel–Fulcher–Tamman model. In spite of the different temperature and concentration dependences observed for each system, a unique scaling behaviour has been evidenced, at relatively low water contents, when the real and imaginary parts of the loss modulus are plotted as a function of a reduced reverse temperature, T 0 /T, being T 0 the values of the arrest temperature as obtained by the Vogel–Fulcher–Tamman fits. The observation of a unique scaling law, for aqueous solutions of polymers characterized by the same average molecular weight but with different end groups, suggests for the establishment of similar hydrogen bonded local structures where water plays a main role, acting as a stabilizer bridging neighbouring polymer chains. The possible physical meanings of the phenomenological fitting parameters are discussed in the framework of recent approaches and the results are compared with literature reports on similar systems.

Investigation of PEG Crystallization in Frozen PEG–Sucrose–Water Solutions: II. Characterization of the Equilibrium Behavior During Freeze-Thawing

Our objective was to characterize, by DSC and XRD, the equilibrium thermal behavior of frozen aqueous solutions containing polyethylene glycol (PEG) and sucrose. Aqueous solutions of (i) PEG (2.5-50% w/w), (ii) sucrose (10% w/v) with different concentrations of PEG (1-20% w/v), and (iii) PEG (2% or 10% w/v) with different concentrations of sucrose (2-20% w/v), were cooled to -70 ° C at 5 ° C/min and heated to 25 ° C at 2 ° C/min in a DSC. Annealing was performed for 2 or 6 h at temperatures, ranging from -50 to -20 ° C. Experiments under similar conditions, on select compositions, were also performed in a powder X-ray diffractometer. Two endotherms, observed during heating of a frozen PEG solution (10% w/v), were attributed to PEG-ice eutectic melting and ice melting, and were confirmed by XRD. At higher PEG concentrations (≥ 37.5% w/w), only the endotherm attributed to the PEG-ice eutectic melting was observed. Inclusion of sucrose decreased both PEG-ice melting and ice melting temperatures. In unannealed systems with a fixed sucrose concentration (10% w/v), the PEG-ice melting event was not observed at PEG concentration ≤ 5% w/v. Annealing for 2-6 h facilitated PEG crystallization. In unannealed systems with a fixed PEG concentration (10% w/v), an increase in the sucrose concentration increased the devitrification but decreased the PEG-ice melting temperature. The PEG-ice melting temperatures obtained by DSC and XRD were in good agreement. In ternary systems at a fixed PEG to sucrose ratio, the T' g as well as the PEG-ice melting temperature were unaffected by the total solute concentration. XRD confirmed the absence of a PEG-sucrose-ice ternary eutectic. When the PEG to sucrose ratio was systematically varied, the PEG-ice and ice melting temperatures decreased with an increase in the sucrose concentration. However, at a fixed PEG to sucrose ratio, the PEG-ice melting temperature, was unaffected by the total solute concentration.

Analysis of ultrafiltration processes with dilatant macromolecular solutions by means of dimensionless numbers and hydrodynamic parameters

Fouling in ultrafiltration was modelled in terms of dimensionless correlations and the Sherwood number using a polyethylene glycol aqueous solution. The rheological nature of this solution was dilatant. Tubular ceramic membranes of 35 kDa molecular weight cut-off were used in the experiments that were performed in turbulent flow conditions. Steady-state fluxes were correlated with several hydrodynamic parameters: Sherwood number, transmembrane pressure, shear rate, shear stress, Reynolds number and crossflow velocity. Power-law fittings were used to analyze experimental data and high correlation coefficients were obtained. Dimensionless correlations showed a similar synergy between membrane and polyethylene glycol solutions and they revealed the formation of a concentration polarization layer and the existence of a critical crossflow velocity among which no polarization phenomena (concentration polarization layer and cake layer) was observed. The results confirmed that rheological properties had less influence on the shear rate than in the case of the shear stress.

Physical properties of epoxy resin/titanium dioxide nanocomposites

AbstractA polymeric nanocomposite system (nanodielectric) was fabricated, and its mechanical properties were determined. The fabricated nanocomposite was composed of low concentrations of monodispersed titanium dioxide (TiO2) nanoparticles and an epoxy resin specially designed for cryogenic applications. The monodispersed TiO2 nanoparticles were synthesized in an aqueous solution of titanium chloride and polyethylene glycol and subsequently dispersed in a commercial‐grade epoxy resin (Araldite® 5808). Nanocomposite thin sheets were prepared at several weight fractions of TiO2. The morphology of the composites, determined by transmission electron microscopy, showed that the nanoparticles aggregated to form particle clusters. The influence of thermal processing and the effect of filler dispersion on the structure–property relationships were identified by differential scanning calorimetry and dynamic mechanical analysis at a broad range of temperatures. The effect of the aggregates on the electrical insulation properties was determined by dielectric breakdown measurements. The optical properties of the nanocomposites and their potential use as filters in the ultraviolet–visible (UV–vis) range were determined by UV–vis spectroscopy. POLYM. ENG. SCI., 2011. © 2010 Society of Plastics Engineers