Aqueous Solutions Of Polyethylene Glycol Research Articles

Influence of 1–alkyl–3–methylimidazolium based ionic liquids on the thermodynamic and transport properties of L(+)–lactic acid in aqueous solutions of polyethylene glycol

In this study, effect of some ionic liquids on the thermodynamic and transport properties of L(+)–lactic acid in aqueous polyethylene glycol solutions have been investigated. Density, speed of sound and viscosity of L(+)–lactic acid in the aqueous solutions of polyethylene glycol, (polyethylene glycol + 1–hexyl–3–methylimidazolium bromide) and (polyethylene glycol + 1–octyl–3–methylimidazolium bromide) were measured at temperatures 288.15–318.15 K. Apparent molar volumes, transfer apparent molar volume, apparent molar isentropic compressibility and viscosity B–coefficient of L(+)–lactic acid were calculated by using experimental data and were discussed in terms of solute–solute and solute–solvent interactions. The results reveal that solute–solvent interactions were decreased by increasing concentration of ionic liquid, length of alkyl group of ionic liquid and temperature.

Physiological quality of seed and seedling performance of crambe genotypes under water stress

ABSTRACT Water stress is a condition that causes physiological changes in different species and even genotypes of the same species. One of the osmotic agents most used to simulate this condition is polyethylene glycol 6000. The aim of this study was to evaluate the effects of water stress on the physiological quality of seeds and performance of seedlings of crambe genotypes. A completely randomized design was used, in a factorial scheme with two genotypes (one cultivar and one line) and five osmotic potentials simulated with aqueous solutions of polyethylene glycol 6000 (control = 0, -0.25, -0.50, -1.0, -1.50 MPa), with four replicates of 50 seeds per treatment. The effects of the treatments were evaluated by means of germination, first count, germination speed index and fresh and dry matter of seedlings. The physiological quality of seeds and the performance of crambe seedlings are negatively affected under water stress from -0.25 MPa on. Seeds of the genotype FMSCR 1101 have greater tolerance to drought stress, regardless of the osmotic potential used.

Solute diffusion into cell walls in solution-impregnated wood under conditioning process III: effect of relative humidity schedule on solute diffusion into shrinking cell walls

This study has focused on solute diffusing into cell walls in solution-impregnated wood under conditioning, process of evaporating solvent. The purpose of this paper was to clarify the RH- (relative humidity-) schedule that promotes the solute diffusion into shrinking cell walls during conditioning. The wood samples impregnated with a 20 mass% aqueous solution of polyethylene glycol (PEG1540) was conditioned with a temperature of 40 °C to the equilibrium point at the RH where the samples swelled maximally. The samples were subsequently conditioned at 40 °C under the schedules including four ways of RH-decrease steps where the cell walls shrunk. The amount of solute (PEGs) diffused into cell walls during the conditioning logarithmically increased with increasing the number of the RH-decrease steps. This was well explained by the theoretical model that describes the solute diffusion into shrinking cell walls. It is clarified from the model that the RH, or moisture content of the sample, should be decreased as gradually as possible to increase the total amount of diffused solute into shrinking cell walls, and that the amount of diffused solute is smaller for the lower moisture content. The model also suggests that effect of change in RH schedule on change in total amount of diffused solute does not depend on solute diffusivity in the sample under drying in a vacuum over phosphorous pentoxide, and that impregnated wood should be conditioned under natural convection rather than forced convection for promoting the diffusion into shrinking cell walls.

Распространение и профилактика пироплазмидозов крупного рогатого скота в Республике Дагестан

Objective of research: Determination of the efficiency of 5% concentration Diminazene aceturate at the dose of 0.25 mg/kg body in combination with polyethylene glycol solution applied against piroplasmidosis in cattle.
 Materials and methods: Trial of the new method of prolonged chemoprevention was carried out in one of the farms of Dagestan, which is unfavorable for piroplasmidosis. Aceturate contained in this drug rapidly inhibits DNA in cells of blood parasites, which leads to their death within several hours. Diminazene aceturate proved to be effective against piroplasmidosis, babesiosis, taleriosis, hemosporidosis of animals. The experiment was conducted on 30 head of cattle divided into 3 groups 10 head in each. Animals of two groups received the preparation and prolongator at the dose of 0,25 mg/kg in the 15% aqueous solutions of polyethylene glycols (PEG), and at the dose of 0,25 mg/kg in the 20% aqueous solutions; the third group served as a control (received the preparation without prolongator). Efficacy of the method was estimated by periodic examination of blood smears from experimental animals for plasmodia in erythrocytes and synchronous measurement of body temperature of animals. 
 Results and discussion: It was found that the method of prolonged chemoprophylaxis applied against piroplasmidosis in animals (at the dose of 5 ml per 100 kg body weight, 6 times every 25 days) enables disease prevention during the whole disease season. Such method allows reducing the number of treatments from 24 to 12-13 times in a season. In addition, data on the distribution of hemosporidia infections among the cattle in the Republic of Dagestan were clarified.

Polyethylene glycol-based ultrasound-assisted extraction and ultrafiltration separation of polysaccharides from Tremella fuciformis (snow fungus)

The polysaccharides of Tremella fuciformis were extracted using an aqueous solution of polyethylene glycol and then separated by ultrafiltration. To obtain the optimal extraction conditions, the effects of different experimental factors on the extraction yield of polysaccharides of T. fuciformis were studied. The experimental results revealed that the optimal polyethylene glycol-based ultrasound-assisted extraction gave a higher extraction yield than that of the common hot water extraction. Using ultrafiltration, the polysaccharides and polyethylene glycol were separated into retentate and permeate solutions, respectively. The recovery and purity of polysaccharides were higher than those of ethanol precipitation. Furthermore, most of polyethylene glycol could be recycled. Therefore, the proposed sample preparation methods were effective in the extraction and separation of polysaccharides, and the recovery of polyethylene glycol.

Study on dimensional stabilization of 12,500-year-old waterlogged subfossil Scots pine wood from the Koźmin Las site, Poland

Abstract The study examines the efficiency of selected conservation treatments proposed for dimensional stabilization of 12,500-year-old waterlogged subfossil Scots pine (Pinus sylvestris L.) tree trunks found at the Koźmin Las site, Poland. The research was done on 198 samples drawn from various parts of the same trunk. Experimental material was characterized on the basis of annual ring width, percentage of latewood, maximum moisture content, density at maximum moisture content, basic density, and wood porosity. Waterlogged wood samples were pre-treated with aqueous solutions of polyethylene glycol (PEG) 300, mixtures of PEG 300 and PEG 4000, a mixture of lactitol and trehalose or a mixture of mannitol and trehalose (nine variants of impregnation) and then freeze-dried or air-dried. Dimensional changes in the wood samples were measured after seasoning to reach equilibrium moisture content at 50% relative humidity and 20 °C. In the majority of the tested conservation treatments, tangential and radial shrinkages or tangential and radial swelling of wood did not exceed 1%. However, differences in dimensional changes depended on the conservation method used and sampling location. Regardless of the state of wood preservation and macroscopic structure features, the best dimensional stability, evaluated on the basis of average anti-shrink efficiency indices, was observed in wood pre-treated with aqueous solutions of 10% PEG 300 + 5% PEG 4000, 10% PEG 300 + 10% PEG 4000 or 10% lactitol/trehalose mixture, and then freeze-dried.

Species dependent iodine extractions in polymer based aqueous biphasic systems: Emerging relations with aggregation number of polymeric micelles

A simple, rapid and sensitive spectrophotometric method has been developed for the extraction and speciation of iodine species; periodate (IO4−), iodide (I−) and povidone-iodine. The proposed method is based on aqueous biphasic system (ABS), obtained by mixing 50% aqueous solution of polyethylene glycol (PEG) of molecular weight 6000 with aqueous solution of inorganic salts (1.5M Na2SO4, 1.5M Na3C6H5O7·5H2O and 1M Na2HPO4) respectively at 300K. Haematoxylin (5mM in 50% PEG), was used as sensing agent for periodate (IO4−). The absorption spectra of iodide and povidone-iodine were measured directly in the PEG solution. The molar absorptivity and sandal sensitivity for IO4−, I− and I2 were 45,562L/mol/cm, 288.88L/mol/cm, 27,736L/mol/cm and 4.69μg/cm2, 3.46μg/cm2, 9.1μg/cm2 respectively. The optimum pH of the salt rich phases were evaluated for extraction of iodine species in aqueous biphasic systems. The extraction of iodine species were preferred at neutral (pH=7) or in basic conditions (pH=9–11). The aggregation numbers of the pure PEG solution as well as that after aqueous biphasic extraction at optimum pH of different salt rich phases were monitored by fluorescence quenching method. This work is the first report on the interdependence between percentage of extraction of iodine species in polymer rich phase and its corresponding aggregation number.

Synthesis and Properties of GO‐Doped Porous Hydrogel Nanocomposites with Semi‐Interpenetrating Network Structure

Superabsorbent hydrogel nanocomposites (SHN) with semi‐interpenetrating polymer network (semi‐IPN) are synthesized by the polymerization of acrylamide monomer in a polyethylene glycol aqueous solution in the presence of the octadecylamine (ODA)‐modified graphene oxide (GO‐ODA) nanosheets. The hydrogel composites are characterized by Fourier transform infrared spectroscopy, thermal gravity analysis, and scanning electron microscopy. The water absorbency of the resulting SHN in distilled water and saline solutions are measured. The results show that doping GO‐ODA nanosheets into hydrogel semi‐IPN would enhance both their salt resistance and water retention. Using a simple freezing‐dry method, porous SHN with macroscopically interconnected pores is prepared, which exhibits excellent separation ability for removal of trace water from oils. Based on their better water absorbency, salt resistance, and excellent oil/water separation ability, the resulting SHN has great potentials in a wide range of applications, for example, oil dehydration, absorption, and separation. image

Effect of molecular weight of polyethylene glycol (PEG), a hydrate inhibitive water-based drilling fluid additive, on the formation and dissociation kinetics of methane hydrate

Polyethylene glycol (PEG), a water-soluble polymer, has been widely used as the most promising polymer for designing hydrate inhibitive water-based drilling fluids. Studies involving the kinetics of methane hydrate formation and dissociation in PEG aqueous solutions may help to develop effective hydrate inhibitive drilling fluids for efficient drilling operation in deep-offshore and hydrate bearing formation. In this work, formation and dissociation kinetics of methane hydrate system have been investigated in an aqueous solution of PEG (with number average molecular weight of 200 and 600 kg/kmol; referred to as PEG-200 and PEG-600, respectively). Different concentrations of PEG, such as 0.2 and 0.4 mass fractions, have been considered for the investigations. Various experiments have been carried out at an initial formation pressure of 7.5 MPa and 5.5 MPa and 263.15 K temperature. The information on the number of moles of methane consumed during hydrate formation, rate of hydrate formation, water-to-hydrate conversion, gas-to-hydrate conversion, number of moles of gas recovered during hydrate dissociation, and rate of hydrate dissociation are being provided in this study. This study provides useful information to use effective combinations of lower and higher molecular weight polymeric systems to develop effective hydrate inhibitive water-based drilling fluid systems suitable for offshore drilling and for hydrate bearing formations.

Studies of Viscosity Coefficient and Expansivity Properties of Aqueous Solutions of Ethylene Glycol and Polyethylene Glycols at 293.15, 298.15 and 303.15 K and at Ambient Pressure

The relative viscosity coefficient $$ \left( {{\raise0.7ex\hbox{$\eta $} \!\mathord{\left/ {\vphantom {\eta {\eta_{0} }}}\right.\kern-0pt} \!\lower0.7ex\hbox{${\eta_{0} }$}}} \right) $$ and volumetric properties of mixtures of water with ethylene glycol (EG) and polyethylene glycols (PEGs) of molecular weights 400, 1000 and 4000 g·mol–1 (PEG-400, PEG-1000 and PEG-4000) in the concentration range of ~0.01 to ~0.5 mol·kg−1, or up to 0.1 volume fraction ( $$ \phi_{2} $$ ), have been measured at three temperatures (293.15, 298.15 and 303.15 K) and at ambient pressure. The data were subjected to analysis by applications of the Jone–Dole equation, Vand’s equation with the viscosity parameters B and D, particle interaction coefficients (Q), Einstein–Simha factor ( $$ \nu $$ ), and hydration number (h) were determined at different temperatures. Using the density data, the limiting apparent molar volumes ( $$ \phi_{\text{V}}^{0} $$ ) at different temperatures, and the limiting apparent molar expansivity ( $$ \phi_{\text{E}}^{0} $$ ) at 298.15 K, were obtained. Positive values of the viscosity B coefficients were observed for all the studied systems; these decrease with increase in temperature, while the D coefficients are also necessary to represent the data, showing specific behavior depending upon the chain length of the polymeric molecules. The larger viscosity increments in excess of the Einstein–Simha volume contributions, and decreasing hydration numbers with increasing temperature, are attributed to the water structure-making effect, solute–solvent hydrogen bond interaction and the presence of hydrophobic interaction between the chain segments of the polymeric molecules. The resulting D coefficients and the virial coefficients are examined from the point of view of solute–solute association.

Environmental cues for germination of the invasive bunch grass Pennisetum ciliare (L.) Link

Responses of seed germination to air temperature, water potential, light, and smoke were studied in the laboratory for seeds of the invasive bunch grass Pennisetum ciliare (L.) Link (syn. Cenchrus ciliare L.; buffel grass). First introduced to North America during the mid-twentieth Century for establishing pastures, this African bunch grass has become an invasive species of concern. Across all the experiments conducted, a low germination was observed for P. ciliare fascicles that never exceeded 30 % at 21 days after sowing. Optimal day/night air temperatures for germination, controlled with an environmental chamber, were 25/15 and 30/20 °C, while extreme temperatures of 15/5 and 45/35 °C inhibited germination. By sowing seeds of P. ciliare under different water potentials, created with aqueous solutions of polyethylene glycol, an optimum of −0.03 MPa led to the highest germination, while no germination was observed at −1.0 MPa. Monochromatic optical filters were utilized to germinate seeds under various wavelengths, of which red (650 nm) and far red (730 nm) led to the highest germination. In addition, seeds that were incubated in the dark had higher germination than those incubated under white light. Incubation in smoke water, which can stimulate germination of pyrophytic species, resulted in a marginal inhibition of germination compared with imbibition with distilled water.

Temperature-induced changes of the packing of double-stranded linear DNA molecules in particles of liquid-crystalline dispersions

The circular dichroism spectra of liquid-crystalline dispersions obtained by phase exclusion of linear double-stranded DNA molecules from aqueous saline solutions of polyethylene glycol (120 ≤ C PEG ≤ 300 mg/mL) have been investigated. The formation of liquid-crystalline dispersions at polyethylene glycol concentrations ranging from 120 to 200 mg/mL was accompanied by the emergence of an abnormal negative band in the spectrum of circular dichroism; this is indicative of cholesteric packing of the double stranded DNA molecules in the particles of the dispersion. Liquid-crystalline dispersions formed at PEG concentrations higher than 220 mg/mL and room temperature did not show any abnormal bands in the circular dichroism spectra; this is indicative of hexagonal packing of double-stranded DNA molecules in the particles of the dispersions. Heating of optically inactive liquid crystal dispersions induced a transition of the dispersions into a different state accompanied by the emergence of an abnormal negative band in the spectrum of circular dichroism. This transition is considered within the concept of the transformation of a hexagonal packing of DNA molecules into a cholesteric packing. A qualitative mechanism of such a transition is proposed that is formulated in the terms of the “quasinematic” layers of double-stranded DNA molecules that change their spatial orientation under the competing influences of the osmotic pressure of the solvent, orientational elasticity of the cholesteric packing, and thermal fluctuations.

Solute diffusion into cell walls in solution-impregnated wood under conditioning process II: effect of solution concentration on solute diffusion

This study focused on solute diffusing into cell walls in solution-impregnated wood during conditioning, process of moderate drying of solvent. To clarify the effect of solution concentration on the diffusion during the conditioning, weight percent gain (WPG) and relative swelling of the wood sample impregnated with an aqueous solution of polyethylene glycol (PEG) polymers at a concentration of 10, 20, 30, 40, or 50 mass% were examined during the conditioning and subsequent drying processes. The relation between the concentration and the relative swelling after all processes, an indicator of the amount of the polymers in cell walls, exhibited a concave-downward curve with a maximum value at 20 mass%. The estimated mass of the polymers in cell walls just before conditioning increased with the concentration. This indicates that the distribution of the polymers changed during conditioning. The estimated mass just before conditioning and the relative swelling after all processes were normalized to the packing ratios of the polymers in cell walls. The ratio after all processes subtracted by that just before conditioning was larger than the ratio just before conditioning, and increased with the concentration up to 20 mass%; after which it decreased. This indicates that the majority of the polymers in cell walls increased during conditioning, and that the amount of the polymers that diffused into cell walls was at the maximum at concentration of 20 mass%. This was explained by two factors: the decrease in the diffusivity into cell walls and in the concentration difference of the polymers between cell walls and cell cavity with the concentration, based on the behavior of WPG during conditioning; and the estimated minimum concentration at which the solution contains the least amount of polymers to fill the cell walls.

Effect of Dissolved Polymer on the Elasticity and Plasticity of a Lyotropic Lamellar Mesophase

SummaryUsing the Surface Force Apparatus (SFA) technique, direct force–distance measurements between mica surfaces immersed in a polymer‐doped lamellar phase are presented. In the aqueous layers separating the charged and undulating bilayers of sodium dodecyl sulfate (SDS)/octanol, water is replaced by a polyethylene glycol aqueous solution (PEG, Mw 20000 g/mol). As the mesophases align with the layers parallel to the solid mica surfaces the measurements yield structural information on the confined mesophases as well as bulk elastic properties. Keeping the membrane volume fraction constant the PEG dissolution results in a marked decrease in the elastic compressibility modulus, . This indicates a softening of the repulsive interactions between the lamellae mediated by polymer adsorption on the bilayers/aqueous solution interface. Insights into the behavior of the mesophases in confined geometries and thereby their stabilization mechanism are gained by noting a plastic contribution due to the presence of edge dislocations in the wedge‐like confinement geometry.

Shaft seal for separation of water and air with low frictional torque

A new type of shaft seal was specifically designed to separate water and air with a low frictional torque. The proposed water-sealing system, which was implemented as a shaft seal, has two hydrated seal lips fabricated from polyvinyl formal. An aqueous solution of polyethylene glycol, which is a non-Newtonian fluid, was injected between the seal lips to support the lubrication and sealing action at the dynamic seal faces. These configurations are based on a biomimetic approach, namely, the mechanism in a natural synovial joint. The water-sealing system exhibited a lower frictional torque than that of oil and mechanical seals, and the friction was not influenced by the applied water pressure. The prevention of water leakage from the water phase to the air phase was also confirmed for water pressure up to 0.8MPa. The proposed water-sealing system may contribute to the improvement of the recovery efficiency of natural energy systems utilizing water flows, tidal currents, and ocean currents, in which the rotating speed of a shaft is low under high water pressure.

Enhancement of Proton Ordering in the Hexagonal Ice in Contact with Polyethylene Glycol Crystal

Heat capacities and spontaneous enthalpy-relaxation effects for 20, 30, and 50 wt % polyethylene glycol (PEG) aqueous solutions subjected to a precooling treatment of quenching or annealing were measured precisely by adiabatic calorimetry. Ice and PEG crystals were produced as eutectoids at low temperatures with leaving a part of the glassy solution, and the eutectic temperature was determined to be 264 K. It was found that a small part of ice in the 20 wt % PEG aqueous solution which had been aged in a range of 200–260 K to enhance its crystalline fraction revealed a proton-ordering phase transition between ice Ih and XI. The phase transition is known to be observed in the ice doped with alkali hydroxides but not to be observed in bulk pure ice because of too long relaxation times for the proton rearrangement to occur; the hydroxide ions work as catalysts for accelerating the rearrangement. According to the present results, we proposed a new scheme for introducing Bjerrum’s defects of the L type at the ice interface in contact with a PEG crystal; the introduction enables the rearrangement to be accelerated and the proton ordering to be achieved.

Solute diffusion into cell walls in solution-impregnated wood under conditioning process I: effect of relative humidity on solute diffusivity

This study focused on solute diffusing into cell walls in solution-impregnated wood under conditioning. The purpose of this paper was to clarify the effect of relative humidity (RH) of the conditioning on solute diffusivity in the impregnated wood. Water evaporation, swelling, and shrinkage of wood samples impregnated with an aqueous solution of polyethylene glycol (PEG) polymer were examined under conditioning at an RH of 11, 32, 55, or 80 % followed by drying under vacuum. Dried samples were observed using a micro-focus X-ray computed tomography instrument. The total amount of PEG polymer diffusing into cell walls during conditioning increased with RH. Theoretical interpretation indicated that this was caused by an increase in polymer (solute) diffusivity as the amount of water (solvent) in samples increased. Temporal variability of the evaporation rate of water and of the swelling rate of the sample also were examined. Solute diffusivity, which was similar at each RH at the beginning of conditioning, decreased during conditioning; this decrease was greater at lower RH values due to a higher evaporation rate.

Investigation of interfacial properties of aqueous two-phase systems by density gradient theory: Dedicated to Prof. Sabine Enders on her 50th birthday and in honor of her previous scientific impact

In this work the interfacial properties of aqueous two-phase systems (ATPS) consisting of an aqueous solution of polyethylene glycol (PEG) and dextran with different molar masses were investigated. To calculate the interfacial properties the density gradient theory was combined with the lattice cluster theory and the Wertheim association theory. With help of this thermodynamic model the liquid–liquid equilibria of the investigated ATPS were calculated in a molar mass range of PEG from 4000 to 20,000g/mol and of dextran from 10,000 to 500,000g/mol; whereas the thermodynamic model was fitted to the phase equilibrium in several selected ATPS. Phase equilibria in all other systems were predicted in a good accordance with experimental data.On the basis of the modelled phase equilibria the interfacial tension was calculated by the density gradient theory in an excellent agreement with experimental data. Moreover, the concentration profile of the phase forming components across the interface was calculated and it could be seen that there is no accumulation of any component in the interface and that the length of interfacial region depends on PEG molar mass.

Controlling the Formation of Ionic-Liquid-based Aqueous Biphasic Systems by Changing the Hydrogen-Bonding Ability of Polyethylene Glycol End Groups.

The formation of aqueous biphasic systems (ABS) when mixing aqueous solutions of polyethylene glycol (PEG) and an ionic liquid (IL) can be controlled by modifying the hydrogen-bond-donating/-accepting ability of the polymer end groups. It is shown that the miscibility/immiscibility in these systems stems from both the solvation of the ether groups in the oxygen chain and the ability of the PEG terminal groups to preferably hydrogen bond with water or the anion of the salt. The removal of even one hydrogen bond in PEG can noticeably affect the phase behavior, especially in the region of the phase diagram in which all the ethylene oxide (EO) units of the polymeric chain are completely solvated. In this region, removing or weakening the hydrogen-bond-donating ability of PEG results in greater immiscibility, and thus, in a higher ability to form ABS, as a result of the much weaker interactions between the IL anion and the PEG end groups.

Liquid–Liquid Phase Separation in Mixed Organic/Inorganic Single Aqueous Aerosol Droplets

Direct measurements of the phase separation relative humidity (RH) and morphology of aerosol particles consisting of liquid organic and aqueous inorganic domains are presented. Single droplets of mixed phase composition are captured in a gradient force optical trap, and the evolving size, refractive index (RI), and morphology are characterized by cavity-enhanced Raman spectroscopy. Starting at a RH above the phase separation RH, the trapped particle is dried to lower RH and the transition to a phase-separated structure is inferred from distinct changes in the spectroscopic fingerprint. In particular, the phase separation RHs of droplets composed of aqueous solutions of polyethylene glycol (PEG-400)/ammonium sulfate and a mixture of C6-diacids/ammonium sulfate are probed, inferring the RH from the RI of the droplet immediately prior to phase separation. The observed phase separation RHs occur at RH marginally higher (at most 4%) than reported in previous measurements made from studies of particles deposited on hydrophobic surfaces by brightfield imaging. Clear evidence for the formation of phase-separated droplets of core-shell morphology is observed, although partially engulfed structures can also be inferred to form. Transitions between the different spectroscopic signatures of phase separation suggest that fluctuations in morphology can occur. For droplets that are repeatedly cycled through the phase separation RH, the water activity at phase separation is found to be remarkably reproducible (within ±0.0013) and is the same for the 1-phase to 2-phase transition and the 2-phase to 1-phase transition. By contrast, larger variation between the water activities at phase separation is observed for different droplets (typically ±0.02).