Adsorption Of Polyethylene Glycol Research Articles

Thermal Properties of Magnetic Nanoparticles Modified With Polyethylene Glycol

Magnetic fluids used in biomedicine have to be biocompatible and therefore the magnetic nanoparticles are modified by different biocompatible materials. In this work the magnetic nanoparticles Fe3O4 sterically stabilized by sodium oleate were prepared by coprecipitation method. Consequently they were modified with polyethylene glycol (PEG) of different molecular weights and different PEG to magnetite Fe3O4 feed weight ratios varying from 0.01 to 30 to produce biocompatible magnetic fluids (MFPEG). The morphology was observed by scanning electron microscopy. The magnetic nanoparticles coated with PEG showed almost spherical shape for all studied systems of MFPEG. Differential scanning calorimetry (DSC) was used to study the adsorption of PEG on magnetic nanoparticles and to determine the maximal amount of PEG adsorbed on the magnetic nanoparticles. The increasing PEG molecular weight leads to the decrease in maximal PEG/Fe3O4 feed weight ratio. In vitro toxicity of the magnetic fluids using cells of skin cancer of mice B16 was tested with the aim to confirm the biocompatibility of the prepared magnetic fluids.

Real-Time Observation of Cu Electroless Deposition: Adsorption Behavior of PEG during Cu Electroless Deposition

The adsorption kinetics of polyethylene glycol (PEG) during Cu electroless deposition was investigated in real-time by measuring the open-circuit potential (OCP) and mass change of a Cu electrode. The addition of PEG during the deposition caused an OCP decrease with a reduction in the deposition rate. It was found that the adsorption of PEG blocked active sites for the adsorption of formaldehyde, a reducing agent, resulting in the suppression effect. The adsorption kinetics of PEG was strongly dependent on the concentration and diffusion coefficient which is directly related to the molecular weight of PEG. The diffusion-controlled adsorption was observed when PEG concentration was low. At high PEG concentrations, the adsorption kinetics was adsorption-controlled when the PEG molecular weight was low and diffusion-controlled when the PEG had a high molecular weight. The strength of the suppression effect was also affected by the molecular weight of PEG: increasing the molecular weight enhanced the suppression effect.

Competitive Adsorption of PEG and SPS on Copper Surface in Acidic Electrolyte Containing Cl−

In damascene copper plating with polyethylene glycol (PEG) and bis– (3–sulfopropyl) disulfide (SPS) as the suppressor and the accelerator respectively, the synergistic effects among additives determine the quality of superfilling. In situ surface–enhanced Raman spectroscopy (SERS) and atomic force microscopy (AFM) were combined with the electrochemical tests to investigate the competitive adsorption between PEG and SPS in the electrolyte containing chloride ions. AFM observation performed at −0.25 V (SCE) shows that PEG accumulate at the prominent position of copper surface gradually in the electrolyte without SPS. When SPS were subsequently added into the above solution, SPS displace most of the PEG molecules to adsorb on the surface within short time (no agitation in solution). In the electrolyte in the presence of both PEG and SPS, SERS data demonstrate that SPS are preferentially adsorbed on copper surface at −0.15 V and −0.25 V (SCE). CV and CA tests carried out at 0rpm and 1000rpm indicate that the adsorption competition between PEG and SPS is apparently potential and convection dependent. These results suggested that SPS can combine with both Cu+ and CuCl to generate weakly-adsorbed intermediate in copper deposition/dissolution, while PEG can only be strongly-chemisorbed on copper surface through CuCl.

The Role of Cl- Ions During the Adsorption of Polyethylene Glycol (MW 20,000) onto a Polycrystalline Gold Electrode

The Role of Cl- Ions During the Adsorption of Polyethylene Glycol (MW 20,000) onto a Polycrystalline Gold Electrode

Study on Influence of Polyethylene Glycol on Dispersion of Pyrite Powder in Aqueous Solution

The influences of three kinds of polyethylene glycol (PEG), namely PEG-200, PEG-1000 and PEG-20000, on the dispersion stability of pyrite powder in aqueous solution were investigated by spectrophotometry. The results indicated that the stability of pyrite powder dispersed in aqueous solution was remarkably dependent upon the molecular weight and content of PEG, pH value of suspension, and ultrasonication power. Among three kinds of polyethylene glycol, PEG-20000 was the most effective additive to improve the dispersion stability and wettability of pyrite powder in water. When 8% PEG-20000 was employed as the dispersant, the best dispersion stability of pyrite powder in aqueous solution could be obtained under the conditions of pH at 5-6 and 100-W ultrasonication power. The FTIR spectroscopic analysis showed that the adsorption between the polyethylene glycol and pyrite ore powder was formed by hydrogen bonding. The adsorption of polyethylene glycol onto the surface of pyrite powder via hydrogen bonding provided a high degree of steric stabilization, which effectively prohibited the aggregation of pyrite powder, and thus the dispersion stability of as-formed aqueous suspension was promoted.

Superheated high temperature to improve size exclusion chromatography separation of polyethylene glycols with chloroform as the mobile phase

In our laboratory, chloroform is increasingly required to be used as the mobile phase for the size exclusion chromatography (SEC) characterization of polyethylene glycol (PEG) derivatives, because some of the derivatives show poor solubility in many other solvents. Four types of SEC columns, all based on highly cross-linked polystyrene–polydivinylbenzene (PS/PDB) and compatible with chloroform, have been tried. However, a problem of using chloroform with all the columns tested is that retention might not be rationalized simply based on the SEC-mechanism even for the PEG standards. It was found that for the PEG standards raising the column temperature can significantly improve the SEC separation. In order to take full advantage of the temperature effect on separation, a system was developed which enables the SEC to be performed at superheated temperatures, i.e., temperatures well above the normal boiling point of the mobile phase. The improved SEC separation at elevated temperatures is most likely due to the combination of reduced adsorption of PEGs by the stationary phase and increased solubility of the solutes in the mobile phase. In this work, the SEC separation operated at temperatures above the normal boiling point of the mobile phase was called “superheated high temperature SEC”.

Thermodynamic Study of PEG (MW 20,000) Adsorption in the Presence of Cl− Anions onto a Polycrystalline Gold Electrode

The adsorption of polyethylene glycol (MW 20,000) (PEG20000) in the presence of Cl− ions onto a polycrystalline gold electrode was studied using a quartz crystal microbalance, AC voltammetry, and chronocoulometry. This study provided new physical insights into the adsorption behavior of this polymer in the presence of chloride ions on a solid electrode in KClO4. Specifically, three potential-based behaviors were observed: the adsorption of PEG20000 was observed to form a condensed phase in the potential range from −0.90 to −0.62 V vs. SCE. The obtained ΔGads values allow for a hypothesis that adsorption occurs by means of hydrogen bridges. In the potential range from −0.62 to −0.10 V vs. SCE, the addition of chloride does not lead to an increased adsorption of PEG20000, but rather to a simple superposition of both adsorption processes. The potential range from −0.10 to 0.35 V vs. SCE is dominated by the adsorption of Cl− ions, and a displacement of adsorbed PEG20000 molecules associated with the adsorption of Cl− anions was observed. Based on the obtained ΔGads values, we propose that, in this potential range, the interaction of the PEG20000 molecules with the Au polycrystalline electrode surface is defined as weak chemisorption via the oxygen atoms.

Adsorption of Polyethylene-Glycols by Nanosized Iron Oxides Particles in Iron Oxides/Polyethylene-Glycol/Water/ Dispersions

The successful application of dynamic light scattering and electron magnetic resonance spectroscopy technique to control the formation of nanosized particles of iron oxides in iron oxides containing aqueous polyethylene-glycol dispersions is shown. The formation of the pegylated iron oxides particles with superparamagnetic properties in this system is established.

Effects of polyethylene glycol and gelatin on the crystal size, morphology, and Sn 2+-sensing ability of bismuth deposits

The influences of citric acid (CA), ethylenediaminetetraacetic acid (EDTA), polyethylene glycol (PEG), and gelatin on the deposition behavior of Bi were systematically investigated through the linear sweep voltammetric (LSV) analysis. Based on the LSV results, deposits plated from a typical solution containing 0.05 M Bi(NO 3) 3·5H 2O and various combinations of complex agents and additives with pH = 3.5 at 1 and 30 mA cm −2 were characterized by scanning electron microscopic (SEM) and X-ray diffraction (XRD) analyses. The adhesion of deposits and the formation of dendrites were respectively improved and inhibited by the adsorption of PEG onto Bi deposits. With adding the above four compounds, a synergistic effect was shown to reach a nano-sized, sphere-like, porous morphology of a Bi deposit at 30 mA cm −2. The crystal size and morphology of Bi deposits were found to affect the sensing ability of Sn 2+ through the square-wave anodic stripping voltammetric (SWASV) analysis.

Molecular mechanism of polyethylene glycol mediated stabilization of protein

The effect of different molar ratios of polyethylene glycol (PEG) on the conformational stability of protein, bovine serum albumin (BSA), was studied. The binding of PEG with BSA was observed by fluorescence spectroscopy by measuring the fluorescence intensity after displacement of PEG with chromophore ANS and had further been confirmed by measuring the intrinsic fluorescence of tryptophan residues of BSA. Co-lyophilization of BSA with PEG at optimum BSA:PEG molar ratio led to the formation of the stable protein particles. Circular dichroism (CD) spectroscopy study suggested that a conformational change had occurred in the protein after PEG interaction and demonstrated the highest stability of protein at the optimum BSA:PEG molar ratio of 1:0.75. Additional differential scanning calorimetry (DSC) study suggested strong binding of PEG to protein leading to thermal stability at optimum molar ratio. Molecular mechanism operating behind the polyethylene glycol (PEG) mediated stabilization of the protein suggested that strong physical adsorption of PEG on the hydrophobic core of the protein (BSA) along with surface adsorption led to the stability of protein.

Fabrication of PEG Thin Films by Irradiation of Atmospheric Pressure Glow Discharge on the Polyethylene Powder

Water insoluble polyethylene glycol (PEG ) films as a core-shell of polymer powder were fabricated by the combination techniques of adsorption of PEG on the powder surfaces and atmospheric glow discharge(APGD) irradiation to the surface to take cross linking reaction of the adsorbed PEG. PEG 2000 was used as the precursor of the core-shell films. The obtained films on the powder surfaces were investigated by XPS,ATR-FTIR and wettability measurement using the capillary raise method.

Physical adsorption of PEG grafted and blocked poly- l-lysine copolymers on adenovirus surface for enhanced gene transduction

Polyethylene glycol (PEG) has been chemically immobilized onto the surface of adenoviruses (ADVs) to reduce non-specific immune response and extend blood circulation time while maintaining the high transduction efficiency of a foreign gene into cells. In this study, ADVs encoding an exogenous green fluorescent protein (GFP) were physically coated with PEG grafted and blocked poly- l-lysine (PLL-g-PEG and PLL-b-PEG) copolymers via ionic interactions to comparatively evaluate their gene transduction efficiency. The surface immobilization of ADVs with the two types of PLL–PEG copolymers exhibited significantly increased GFP transduction activity, compared to that of naked ADVs. ADVs coated with PLL-b-PEG showed higher extent of GFP expression than those with PLL-g-PEG under serum conditions. For PLL-g-PEG copolymers, the substitution degree of PEG in the PLL backbone greatly influenced the gene expression level. Additionally, ADVs modified with PLL-b-PEG exhibited greater transduction efficiency for bone marrow derived human mesenchymal stem cells compared to naked or PLL coated ADVs in the serum condition. This study suggests that enhanced ADV gene transduction efficiency can be attained for various cells by simply coating PLL-b-PEG on the surface.

Synergistic effect of halide ions and polyethylene glycol on the corrosion inhibition of aluminium in alkaline medium

AbstractThe corrosion inhibition of aluminium in alkaline medium was studied at 30 and 40°C in the presence of polyethylene glycol (PEG) using gravimetric (weight loss) and thermometric techniques. The effect of halides (KCl, KBr, and KI) on the inhibitory action of PEG was also studied. It was found that PEG acted as inhibitor for aluminium corrosion in the alkaline medium. Inhibition efficiency increased with increasing inhibitor concentration. An increase in temperature led to increase in both the corrosion rate and inhibition efficiency in the absence and presence of inhibitor and halides. Phenomenon of chemical adsorption mechanism is proposed from the values of Ea, Qads, and ΔG obtained. The adsorption of PEG on the surface of aluminium was found to obey Flory–Huggins and Temkin adsorption isotherms. The synergism parameter, S1 evaluated was found to be greater than unity indicating that the enhanced inhibition efficiency caused by the addition of halides is synergistic in nature. The inhibition efficiency, surface coverage and synergism parameter increased in the order; I−> Br−> Cl− showing that a joint adsorption of PEG and halide ions on aluminium plays a significant role in the adsorption process. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Inhibition of Copper Deposition by Polyethylene Glycol and Chloride: II. Analysis and Application

A comprehensive model for the effect of polyethylene glycol (PEG) and on reduction developed in Part I of this study [ Huerta Garrido and Pritzker , J. Electrochem. Soc. , 156 , D36 (2009) ] is further analyzed in Part II. On the basis of the model, the sharp loss of inhibition at a critical potential during cathodic scans occurs whenever the PEG adsorption density decreases below the minimum amount required to completely cover the electrode. When high additive concentrations are used, the electrode remains completely covered by the inhibiting film throughout the scan and, thus, the current for reduction rises more gradually with overpotential. Excellent agreement between the computed and measured current-potential curves during both forward and reverse directions of cyclic scans is obtained for each solution investigated in this study. Furthermore, analysis of the model reveals that hysteresis in these cyclic scans occurs whenever the electrode goes from a state where it is completely covered by PEG to one where it is only partially covered during the forward scan.

Refolding of lactate dehydrogenase by zeolite beta

We used zeolite beta as an adsorbing matrix to refold recombinant lactate dehydrogenase (LDH) protein collected as an insoluble aggregate from a bacterial expression system. The adsorption isotherm revealed that 1 g of zeolite adsorbed 200 mg of denatured LDH solubilized with a buffer containing 6 M of guanidine hydrochloride. The pH of the buffer had little effect on the adsorption, but this property was abolished by preincubation of the zeolite with polyethylene glycol (PEG) in a weight ratio of 1:10. These data suggest that the adsorption of LDH depends on the hydrophobicity of the zeolite surface, and that the adsorption of PEG to zeolite is sufficient to release LDH from its surface. LDH was thus released by refolding buffer containing PEG and arginine, and soluble LDH was obtained in its active enzymatic form. The addition of arginine dramatically increased the yield of LDH in a dose-dependent manner. The overall refolding efficiency was optimized to 35%.

Interactions of Chloride and Polyethylene Glycol in Acidic Copper Sulfate Electrolyte

The individual roles of and the interactions between two additives, chloride and polyethylene glycol (PEG), in copper electrochemical deposition (ECD) from an acidic copper sulfate solution are studied with electrochemical methodologies, such as linear sweeping voltammetry (LSV), chronoamperometry, and ac electrochemical impedance spectroscopy (EIS). The LSV results reveal current inhibition in the presence of both PEG and chloride in the solution and role of chloride in copper ECD. The EIS results reveal a low-frequency inductive loop associated with PEG adsorption, an intermediate capacitive loop associated with a chloride bridge, and a high-frequency capacitive loop related to double-layer charging. A detailed reaction mechanism is proposed. The mechanistic EIS model based on the reaction mechanism represents the experimental EIS data very well.

Adsorption of SDS and PEG on Calcium Fluoride Studied by Sum Frequency Generation Vibrational Spectroscopy

The adsorption of sodium dodecyl sulfate (SDS) from aqueous solution onto a calcium fluoride substrate (CaF(2)), in the presence of polyethylene glycol (PEG) of different molecular weights, has been investigated using the interface specific nonlinear optical technique of sum frequency generation (SFG) vibrational spectroscopy. Spectra of adsorbed SDS (in the C-H stretching region) were recorded at the surface of a CaF(2) prism in contact with SDS solutions at concentrations up to the cmc (8 mM) of the pure surfactant and in contact with binary solutions containing SDS and PEG with molecular weights from 400 to 12 000. In contrast with SFG spectra from the same combinations of surfactant and polymer on a hydrophobic surface, there was no evidence of spectra arising from the actual polymer adsorbed on CaF(2) at any polymer molecular weight either in the absence or presence of surfactant. However, there was indirect evidence for the presence of adsorbed polymer from changes in the SDS SFG spectra in the presence of polymer compared with spectra when the polymer was absent. The SFG spectra of SDS at 0.8 mM were closely similar to each other at all polymer molecular weights and different from the spectra in the absence of the polymer. The spectral differences between the polymer present and polymer absent was much smaller when the solution concentration of surfactant was 8 mM.

Effect of Cl − on the Adsorption–Desorption Behavior of PEG

The adsorption–desorption behavior of polyethylene glycol (PEG) on the cathode surface in copper plating solution with and without was investigated by cathodic polarization measurement and electrochemical impedance spectroscopy (EIS) measurement. Cathodic polarization analyses show that the inhibiting effect of PEG is potential-dependent in the solution with and without . EIS analyses suggest that the adsorption of PEG is strengthened by the existence of , and both adsorption and desorption potential range of PEG are widened by the existence of , which is attributed to the different adsorption mode of PEG. The adsorption of PEG in the solution without is in the form of and , which adsorb on the cathode surface mainly by two acting forces, the van der Waals force and the electrostatic force. In the solution with , the adsorption of PEG is mainly in the form of and . It is due to the specific adsorption ability of on the electrode surface that the adsorption of PEG is greatly strengthened compared with that in the solution without . Thus, the adsorption and the desorption potential range of PEG are widened, and PEG shows a much stronger inhibiting effect on copper deposition in a wider potential range.

The co-dispersion of silicon carbide with nano-C and B 4C in aqueous ethanol solution

In this paper, the mixture of de-ionized water and ethanol was used as the solvent for SiC particles. SiC can be well co-dispersed in alkaline aqueous ethanol solution with the sintering aids nano-C and B 4C, especially when the pH value is between 9 and 10. Polyethylene glycol (PEG) as the dispersant, it can improve the dispersion of SiC slurry. The adsorption of polyethylene glycol in SiC slurries was measured by thermal gravimetric (TG) and differential thermal analysis (DTA) in argon atmosphere. It was found that the adsorption of polyethylene glycol on the surface of SiC, nano-C and B 4C decreased with the increase of pH value and most free dispersant remained in the suspension at higher pH value. The granulated and flowable powder was prepared by spraying processing.

Temperature Study of Nonionic Polymers Adsorption at the Alumina—Solution Interface

The temperature influence of the structures of polyvinyl alcohol (PVA) and polyethylene glycol (PEG) adsorption layers on the alumina surface was studied. The amount of polymer adsorbed, the surface and diffuse layer charge of Al2O3 particles in the absence and presence of the polymer, and the thickness of polymer adsorption layers were determined in the 5°–40°C temperature range. An increase of PVA and PEG adsorption with an increase of temperature was observed. It is caused by conformation changes of polymer macromolecules from the coil structure to more and more stretched conformation when the temperature increases. Such a behavior was confirmed by the parameters calculated from the experimental data (Rh—hydrodynamic radius of a polymer coil in the solution, δ—thickness of the polymer adsorption layer, Rs—radius of a sphere equivalent to the volume that falls per a macromolecule in the adsorbed layer). From the comparison of the values of diffuse layer charge and surface charge, the main factor influencing the ζ potential changes was determined. The free energy of PVA and PEG adsorption was calculated using the ζ potential data.