Aqueous Solutions Of Polyethylene Glycol Research Articles

Structure of polyethylene glycol/water mixtures as a separation medium of aqueous two-phase extraction systems studied by equilibrium analysis of thiocyanato complexation of Cobalt(II)

Aqueous two-phase systems (ATPS) utilizing polyethylene glycol (PEG) have been successfully used for the separation of various organic and inorganic compounds as an environmentally benign extraction method. However, a fundamental understanding of the role of the hydration structures around PEG chains in solute partitioning in ATPS remains elusive although it has been considered that PEG molecules are involved in separation. In the present work, the equilibria of Co(II) thiocyanate complexation reaction in aqueous PEG solutions were studied by spectrophotometry with varying ethylene oxide chain length and concentration of PEG. From the formation constants of the tetrahedral and octahedral Co(II) thiocyanate complexes obtained, a microheterogeneous structure consisting of pseudo phases formed by hydration of ethylene oxide (EO) chain and terminal hydroxyl (OH) groups in the PEG molecule in addition to the bulk water phase was estimated. It was revealed that the formation of tetrahedral Co(NCS)42− complex proceeds in the EO pseudo phase by the involvement of hydrophobic ethylene groups, while the OH phase and the bulk phase inhibit the progress of the reaction. This indicates that Co(NCS)42− is stable in hydrophobic hydration structure of water around the EO moiety. The EO phase imparts hydrophobicity to aqueous PEG solutions and plays a predominant role in partition of solute molecules in PEG-based ATPS.

Evaluations of ethylene glycol and polyethylene glycol aqueous solutions using a hybrid sensor of surface plasmon resonance and quartz crystal microbalance

A hybrid sensor based on surface plasmon resonance (SPR) and quartz crystal microbalance (QCM) was prepared. One of the electrodes of the QCM sensor had a grating structure to enable SPR excitation. The SPR property was investigated through the transmission of the visible-light spectrum. The theoretical calculation showed that the experimental values almost corresponded to the theoretical ones; this suggests that the transmitted light dips were due to SPR. In order to investigate the usefulness of this hybrid sensor, the characteristics of SPR and the oscillation frequency drops of QCM (ΔF QCM) were investigated for aqueous solutions of ethylene glycol and polyethylene glycols with various degrees of polymerization. The position and slope of the SPR dip wavelength and the ΔF QCM curves depended on the degree of polymerization, suggesting that the sensor can be used to evaluate a solution property and/or discriminate a solute material.

Accelerating Macroscale Superlubricity through Carbon Quantum Dots on Engineering Steel Surfaces

AbstractMacroscale superlubricity on engineering steel surfaces offers a promising solution for minimizing friction and wear in engineering applications. However, achieving superlubricity typically requires a long running‐in period, which may result in significant wear for the friction pair. Herein, a new lubricant with superlubricating properties is rationally designed by using polyethylene glycol (PEG) and critic acid (CA) under complexing effect with a running‐in period of about 800 s. Importantly, the introduction of carbon quantum dots (CQDs) obtained from the pyrolysis of CA into PEG aqueous solution shortens the running‐in period for achieving macroscale superlubricity (µ ≈ 0.005) between steel/steel contact to 44 s. The corresponding wear rate (1.15 × 10−7 mm3 N−1 m−1) on the steel disk is reduced by 77% due to the shorter running‐in time. Furthermore, the surface analysis combined with the molecular dynamics simulations demonstrates that CQDs easily adsorb on the surface of the friction pair, forming a carbon film that reduces interaction energy between the lubricant molecules and the substrate. This work provides new insights into the lubrication mechanism of CQDs and contributes to the design of liquid superlubricants with short running‐in periods and low wear rates on engineering steel surfaces.

Fabrication of high-strength and anti-hydration water-soluble calcia-based ceramic core modified with nano-ZrO2 via direct ink writing method

An additive manufacturing method, named direct ink writing (DIW), was adopted to fabricate high-strength and anti-hydration water-soluble calcia-based ceramic cores in this paper. The green bodies were prepared using calcium carbonate as precursor material, polyethylene glycol aqueous solution as binder and nano-ZrO2 as modifier, and then calcia-based ceramic cores were obtained by sintering at 1400 °C. The effect of different nano-ZrO2 contents on the properties and microstructure of the calcia-based ceramic cores was investigated. The results indicated that when the nano-ZrO2 content increased, the shrinkage rate of the ceramic cores in the X, Y and Z directions gradually decreased, the bending strength increased significantly and the hydration resistance enhanced, while the water-soluble rate decreased. The incorporation of nano-ZrO2 led to an augmentation in the CaZrO3 phase content within the CaO matrix of the calcia-based ceramic core. The CaZrO3 phase was interconnected and uniformly distributed around the CaO grain boundaries, which was the reason for increasing the bulk density of the ceramic core and increasing the sintering neck, reducing linear shrinkage rate and improving bending strength, while decreasing the water-soluble rate. The high-strength and anti-hydration water-soluble calcia-based ceramic core is achieved by adding 10 wt% nano-ZrO2, with the bending strength of 11.68 MPa, the shrinkage rate of 16.72%, 48h moisture absorption rate of 5.88%, and the water-soluble rate of 4.21 g/(s·m2) in 60 °C water, which is suitable for the rapid casting of the complex internal castings.

Studies of monomer–dimer equilibria of methylene blue as a probe to investigate the solute–solvent and hydrophobic interactions in aqueous solutions of polyethylene glycols at 298 K

Electronic absorption spectrums of methylene blue (MB) in the concentration range wherein monomer–dimer equilibria exist have been systematically investigated in aqueous solutions of polyethylene glycols (PEG's) having molar mass 400, 1000 and 4000 g∙mol–1, at 298 K. The data on the absorption spectrums (550–700 nm) of MB are resolved to obtain monomer and dimer spectrums as well the geometrical details of the species (such as oscillatory strength, dipole moment etc.) are calculated. The molar absorption extinction coefficients for monomer and dimer cations of MB, the dimer dissociation constant values are calculated as a function of PEG concentrations. It has been noted that, absorption maximum occurs at 664 ± 1 and 605 ± 1 nm, respectively, for monomer and dimers which do not get affected much by presence of polymeric molecules and the data show perfect obedience of Beer–Lambert's law. The changes in dimer geometry from sandwich type to end–on–end type have been studied by applying exciton theory of Kasha et al. The dimer dissociation constant values at finite as well for infinitely dilute concentration of PEG's exhibit orderly amendment with respect to molar mass of PEG's and alteration in chain length of molecules. We report the free energy changes of transfer of dimeric cations of different concentrations from water to aqueous solutions of PEG's of fixed concentration, that is, to probe the interactions of water and PEG molecules with a hope of getting information about salting–in/salting–out effects, as well of binding of dye molecules with PEG's. We have suggested complexation of end hydroxylic groups of PEG's with dimer cations. The results are further interpreted as salting–in of PEG complex with MB–dimers only in the limit of infinite dilution (solute–solvent interactions) while salting–out of these complexed species is observed as a function of MB–dimer concentration.

Improved bleached eucalyptus kraft pulp-based tissue papers incorporating wet-strength resins

Abstract Common tissue paper manufacturing trends aim at partial or total replacement of softwood pulp with hardwood pulp for its production, such as bleached eucalyptus kraft pulp (BEKP), in order to optimize the process and the final product properties such as softness. However, the use of a single type of hardwood fiber results in lower strengths of both wet and dry webs. To maintain necessary strength and desired properties, the incorporation of several additives is often required. In this context, low molecular weight polyethylene glycol (PEG) and different wet strength resins, such as polyamideamine-epichlorohydrin (PAE) and glyoxalated polyacrylamide (GPAM) resins, were combined to achieve an innovated product with improved properties. In particular, wet and dry tensile strength was significantly improved when combining PEG and wet strength resins, especially observed in tissue papers prepared with PAE resin, high-charge cationic agent and bulk applied aqueous PEG solution. Noteworthy that water absorption capacity and softness of tissue paper were not critically affected by PEG incorporation, regardless of application method used (in bulk or by spray).

Optical Polymorphism of Liquid-Crystalline Dispersions of DNA at High Concentrations of Crowding Polymer.

Optically active liquid-crystalline dispersions (LCD) of nucleic acids, obtained by polymer- and salt-induced (psi-) condensation, e.g., by mixing of aqueous saline solutions of low molecular weight DNA (≤106 Da) and polyethylene glycol (PEG), possess an outstanding circular dichroism (CD) signal (so-called psi-CD) and are of interest for sensor applications. Typically, such CD signals are observed in PEG content from ≈12.5% to ≈22%. However, in the literature, there are very conflicting data on the existence of psi-CD in DNA LCDs at a higher content of crowding polymer up to 30-40%. In the present work, we demonstrate that, in the range of PEG content in the system above ≈24%, optically polymorphic LCDs can be formed, characterized by both negative and positive psi-CD signals, as well as by ones rather slightly differing from the spectrum of isotropic DNA solution. Such a change in the CD signal is determined by the concentration of the stock solution of PEG used for the preparation of LCDs. We assume that various saturation of polymer chains with water molecules may affect the amount of active water, which in turn leads to a change in the hydration of DNA molecules and their transition from B-form to Z-form.

Hydration Numbers of Polyethylene Glycols Based on a New Viscosity Model

AbstractDue to the high solubility in water and the structural compatibility of polyethylene glycol with water molecules, it is a good model system for studying the mechanisms of interaction between water and biopolymers. The behavior of biopolymers in living organisms strongly depends on the hydration of macromolecules in the aquatic environment. In this work the effective hydration numbers of polyethylene glycols are determined using a new viscosity model developed for electrolytes and experimental data on the viscosity of dilute aqueous solutions of polyethylene glycols (300–35000). The calculated hydration numbers are in good agreement with the literature data and increase with increasing molecular mass of polyethylene glycol: as the molecular mass increases, starting from a molecular mass of 1000, the chain begins to fold in on itself, forming segment‐segment interactions, trapping additional, more loosely bound water between the segments. Based on the dependence of the intrinsic viscosity on the molecular mass according to the Mark‐Houwink equation, it is shown that PEGs are the flexible polymers and highly soluble in water.

Volumetric, compressibility and conductometric studies of L-histidine in aqueous poly ethylene glycol solutions at different temperatures

Volumetric, compressibility and conductometric studies of L-histidine in aqueous poly ethylene glycol solutions at different temperatures

Effects of temperature, provenance, drought stress and salinity on seed germination response and early seedling stage of Thymus atlanticus (Ball) Roussine

Thymus atlanticus (Ball) Roussine is a valuable aromatic and medicinal species endemic to Morocco. Climate change and anthropogenic threats are factors driving this species to vulnerability and extinction. Therefore, the current study aims to examine the effects of provenance, temperature, drought stress, and salinity on the germination parameters of T. atlanticus seeds and seedling vigor. Seeds are collected from two provenances (Saghro and Tizi n’Telghemt). Treatments included six alternating temperature regimes (10/0, 15/05, 20/10, 25/15, 30/20, and 40/25 °C), five osmotic potentials of aqueous solutions of polyethylene glycol (PEG-6000) (0, −0.1, −0.3, −0.6, and −0.9 MPa), and five concentrations of sodium chloride (NaCl) (0, 1, 2.5, 5, and 7 g/l). The two-way ANOVA test reveals that alternating temperatures, drought, salinity, and their interactions with provenance almost all have a significant impact on germination parameters. However, no significant effect is registered for the interaction between provenance and alternating temperatures on the final germination percentage (FGP). The highest FGP is recorded at several alternating temperatures (15/05, 20/10, 25/15, and 30/20 °C), and the maximum one is at 20/10 °C for both populations (Saghro and Tizi n’Telghemt, respectively 93% and 89%). This temperature regime is also the best in terms of germination time and speed. The most vigorous seedlings are obtained at 20/10 and 30/20 °C for Tizi n’Telghemt and Saghro populations, respectively. Concerning salinity and moisture stress, the results show that the increase in NaCl and PEG-6000 concentrations leads to a significant reduction in the germination capacity (FGP) and seedling vigor index as well as an increase in the mean germination time (MGT) of the two populations studied. The Saghro population tolerates the studied stresses better than the Tizi n’Telghemt population. These results may serve as guidelines for the domestication and rehabilitation of this medicinal plant.

Temperature dependent micellization behavior of as synthesized anionic SAILs in aqueous nonionic polymer solutions: conductivity, UV-visible probe and antimicrobial studies

As synthesized surface active ionic liquids (SAILs), Tetrapropylammonium Dodecylsulfate (TPADS), and Tetrabutylammonium Dodecylsulfate (TBADS) have been characterized by FTIR, 1H-NMR and 13C-NMR spectroscopic techniques. Conductometric and UV-Visible probe investigations have been attempted to study the aggregation behavior of these synthesized SAILs in aqueous solution of polymers Polyvinylpyrrolidone (PVP) and Polyethylene glycol (PEG) at different temperatures and concentrations. Two breaking points were identified from κ vs [SAILs] plots. First, the critical aggregation concentration (CAC) is recognized with the polymer-SAILs binding and the second being regarded as critical micellar concentration (CMC), suggested to represent saturation point for Polymer-SAIL aggregation. Thermodynamic parameters of micellization ( Δ G m o , Δ H m o and Δ S m o ) are rationalized in terms of interactions prevailing between hydrophobic and hydrophilic regions of SAIL-Polymer system. Micellization process for the blend of SAIL-PVP is found to be more favored than SAIL-PEG at all temperatures. Further, the effect of PVP on the antimicrobial activities of TPADS/TBADS has been tested by measuring zone of inhibition which accounts for higher effectiveness of PVP-SAILs system against gram positive bacteria (Bacillus cereus and Staphylococcus aureus) as compared to gram negative bacteria (Pseudomonas aeruginosa).

Comments Regarding “Volumetric, Acoustic, Viscometric Properties, and Solute–Solvent Interactions of Metformin Hydrochloride in Aqueous Solution of Polyethylene Glycol (PEG 4000) at Different Temperatures (T = 288.15–318.15 K)”

Comments Regarding “Volumetric, Acoustic, Viscometric Properties, and Solute–Solvent Interactions of Metformin Hydrochloride in Aqueous Solution of Polyethylene Glycol (PEG 4000) at Different Temperatures (T = 288.15–318.15 K)”

Macroscale superlubricity induced by film-forming polymer brush-grafted colloidal additives

HypothesisModifying surfaces with concentrated polymer brushes (CPBs) is an effective way to reduce friction of tribo-pairs lubricated with liquids. We investigate the hypothesis that colloids grafted with CPBs (hybrid colloids) can deposit onto tribo-substrates by varying the solvent quality with respect to the polymer, in order to obtain ultra-low coefficients of friction (CoFs), so-called superlubricity. ExperimentsHybrid colloids are synthesized and characterized, and a dynamic light scattering compares their swellings in aqueous solutions of glycerol or polyethylene glycol. A mini-traction machine with viscoelastic tribo-pairs is used for lubrication experiments. Adsorption of colloids and film structures are tested using a quartz crystal microbalance and an atomic force microscope. FindingsThe solvent controls whether hybrid colloids spontaneously adsorb to the substrate under quiescent conditions or require contact forces to enable (tribo-)deposition. In both cases, the friction in the boundary-mixed lubrication regimes is lower upon increasing the degree of swelling of CPBs and upon increasing coverage of deposited colloids. The greatest lubrication enhancement and surface coverage occur for the spontaneously adsorbed colloids, with ultra-low CoFs of order 10-3 over a large range of speeds. The results demonstrate the potential for hybrid colloids to be used as solvent dispersible “friction modifier additives”.

Tribological properties of bis(2-hydroxyethyl)ammonium oleate in glycerol and polyethylene glycol aqueous solutions

The use of eco-friendly water-based lubricants can benefit manufacturing processes and the health of operating personnel while reducing environmental pollution. This study investigates the tribological properties of bis(2-hydroxyethyl)ammonium oleate protic ionic liquid (PIL) as a potential additive to enhance tribological properties in aqueous solutions of glycerol and polyethylene glycol. The studied concentration of bis(2-hydroxyethyl)ammonium oleate was in the range of 0.1 to 1.5 wt%. The base fluids contained 50 wt% glycerol and 12 wt% polyethylene glycol, respectively. The physicochemical properties, wettability, and corrosion-prevention ability were evaluated. Lubricity was investigated using a ball-on-plate configuration in reciprocation mode and a four-ball tribometre. The wear scars were analysed using optical microscopy, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The introduction of PIL into the base fluids enhanced their wettability and ability to prevent corrosion. Furthermore, the PIL improved the wear and reduced the friction coefficient of both fluids. Moreover, their load-carrying ability was enhanced. Based on the observed results, friction and wear reduction mechanisms were suggested.

Hemolymph osmolality in mollusk Lymnaea stagnalis during acute experimental hyperglycemia

It has been established that the development of hyperglycemia, accompanied by a multiple increase in the hemolymph glucose content (up to 4.0 – 4.5 mmol/L), doesn’t lead to any significant changes in Lymnaea’ s hemolymph osmolality. Incubation of mollusks in 100 mmol/L aqueous solution of polyethylene glycol 200 for 2 h causes a 1.4-fold increase in hemolymph osmolality (up to 210 mosmol/kg) compared to the control level.

Balsam Poplar Buds: Extraction of Potential Phenolic Compounds with Polyethylene Glycol Aqueous Solution, Thermal Sterilization of Extracts and Challenges to Their Application in Topical Ocular Formulations.

Phenolic compounds of natural origin have been valued for their beneficial effects on health since ancient times. During our study, we performed the extraction of phenolic compounds from balsam poplar buds using different concentrations of aqueous polyethylene glycol 400 solvents (10–30% PEG400). The aqueous 30% PEG400 extract showed the best phenolic yield. The stability of the extract during autoclave sterilization was evaluated. The extract remained stable under heat sterilization. Ophthalmic formulations are formed using different concentrations (8–15%) of poloxamer 407 (P407) together with hydroxypropyl methylcellulose (0.3%), sodium carboxymethyl cellulose (0.3%) or hyaluronic acid (0.1%). Physicochemical parameters of the formulations remained significantly unchanged after sterilization. Formulations based on 12% P407 exhibited properties characteristic of in situ gels, the gelation point of the formulations was close to the temperature of the cornea. After evaluating the amount of released compounds, it was found that, as the concentration of polymers increases, the amount of released compounds decreases. Formulations based on 15% P407 released the least biologically active compounds. Sterilized formulations remained stable for 30 days.

New Autonomous Water-Enabled Self-Healing Coating Material with Antibacterial-Agent-Releasing Properties.

A new autonomous water-enabled self-healing coating with antibacterial-agent-releasing capability was developed for the first time by precipitating an aqueous solution of hydrogen-bonded tannic acid (TA) and polyethylene glycol (PEG) (TA: 5 mg/mL; PEG: 5 mg/mL with MW = 100 kDa) to form a smooth, uniform coating layer with an average roughness of 0.688 nm and thickness of 22.3 μm on a polymethyl methacrylate (PMMA) substrate after 10 min of incubation. Our method is cost- and time-efficient, as the hydrophilic coating (water contact angle = 65.1°) forms rapidly, binding strongly to the PMMA substrate (adhesive energy = 83 mJ/m2), without the need for pretreatment or surface modification, and is capable of rapid self-repair (approximately 5 min) through hydrogen bonding in aqueous media. Furthermore, adding 0.5 mg/mL of chlorhexidine acetate (CHX), a commonly used antibacterial agent in dentistry, into the TA–PEG emulsion allowed the release of 2.89 μg/mL of the drug from the coating layer, which is promising for actively inhibiting the vitality and growth of bacteria around PMMA dental restorations. The use of CHX-loaded TA–PEG hydrogen-bonded complexes is highly favorable for the fabrication of an autonomous self-healing biocoating with active antibacterial-agent-releasing capability, which can be applied not only in dentistry but also in other medical fields.

Structure and Intermolecular Interactions in Aqueous Solutions of Polyethylene Glycol.

Aqueous solutions of polyethylene glycol are studied by small-angle neutron scattering over a broad range of polymer molecular masses and concentrations. The scattering data were modeled by a Gaussian chain form factor combined with random phase approximation, which provided good fits over the whole studied concentration range. The results showed that polyethylene glycol in the molecular mass range –20 kDa in water at physiological temperature T = 37 C behaves like a random coil in nearly theta solvent conditions. The obtained results serve as a reference for the description of complex mixtures with PEG used in various applications.

Characterization of hydrogen bond network of waters around polyethylene glycol by broadband dielectric spectroscopy

Polyethylene glycol (PEG) is a well-known water retention agent in biomedical products, the hydration efficiency of which is affected by its molecular weight. Using a broadband dielectric spectroscopy (100 MHz–18 THz), the hydration state of PEG aqueous solutions with various molecular weights was quantitatively evaluated. As the molecular weight increases, the restriction strength of hydration water increases in potency, while the number of hydration water molecules decreases. Owing to the opposite changes in hydration number and restriction strength, the measured collective hydrogen bond (HB) strength shows negligible molecular weight dependence. PEG with larger Mw produces a more heterogenous HB network. The internal folding and twining caused by the growth of the PEG chain obstruct the proper exposure of hydrophilic part of the monomer producing less hydration waters. The evaluation result supports an application of PEGs with low molecular weight in contact lens package solutions.

Ultrasonic and Volumetric Studies of Aqueous Solution of Polyethylene Glycol

In present study an attempt has been made to analyse the molecular interactions of aqueous solution of polyethylene glycol of molecular weight 200 at different concentration and at different temperature by determining density, viscosity, and ultrasonic velocity. Various parameters like, adiabatic compressibility acoustic impedance and intermolecular free length have been calculated at different temperatures and at 0.50% concentration. This study helps to understand the physio-chemical behavior of macro molecules with change in temperature and concentration.