Poly Ethylene Oxide Chains Research Articles

A polyaniline + polyethylene oxide mixture as a composite polymer positive electrode in solid-state secondary batteries

We present here a physico-chemical and electrochemical study of a polyaniline (PAni) + polyethylene oxide (PEO) mixture prepared from a codissolution of both polymers in 1-methyl-2-pyrrolidinone. SEM observations showed that the best homogeneity of the polymer material was obtained when PAni was protonated directly in solution. FT-IR spectroscopic experiments showed that the entanglement of the PEO and PAni chains hindered the return of the PEO chains to their more stable helical form. XPS analyses of the films surface gave a 40% doping of the aniline units by the anions of the salt Li[N(CF 3SO 2) 2]. High gravimetric capacities of the order of 200 A h kg −1 (related to the PAni mass in the mixture) were extracted during the charge/discharge of the polymer material in a PEO based solid electrolyte. The best performances were obtained for PEO proportions comprised between 30 and 60 wt.%. Moreover, good cycling stability was observed. The PAni + PEO material could be suitable for use as an electrode material in high cycle life electrochemical devices.

Plasma protein adsorption and platelet adhesion onto comb-like PEO gradient surfaces.

Comb-like polyethylene oxide (PEO) surfaces were prepared on low-density polyethylene (PE). The comb-like PEO chain density was changed gradually along the sample lengths by corona discharge treatment with gradually increasing power and the following graft copolymerization of poly(ethylene glycol) monomethacrylate macromers (PEO-MA). The macromers with different PEO repeat unit, 1, 5, and 10, were used. The prepared comb-like PEO gradient surfaces were characterized by water contact angle, Fourier transform infrared spectroscopy in the attenuated total reflectance mode, and electron spectroscopy for chemical analysis. All these measurements indicated that the PEO chains are grafted on the PE surface with gradually increasing density of PEO. Plasma protein adsorption and platelet adhesion on the PEO gradient surfaces decreased with increasing PEO chain length and surface density. As observed by scanning electron microscopy, PEO10-MA-grafted surface with high PEO density was very effective in preventing protein adsorption and platelet adhesion and did not activate the platelets.

High affinity polyethylene oxide for improved biocompatibility.

Albumin passivation methods are based on the premise that a confluent layer of conformationally intact albumin will provide a biocompatible surface. However, albumin in contact with foreign surfaces tends to denature, and other proteins will adsorb to the surface, making the albumin passivation theory difficult to test. To overcome these two limitations, it was necessary to have a nondenaturing ligand specific for albumin attached to the surface by a long chain polyethylene oxide (PEO), which is known to have low protein binding. Clinical reports suggest no denaturation of albumin upon binding with warfarin, a drug known to have high albumin affinity. Thus, we tethered warfarin to glass.

Preparation and Characterization of Comb-like PEO Gradient Surfaces

Comb-like polyethylene oxide (PEO) gradient surfaces where the density of comb-like PEO chains changes gradually along the sample length were prepared on low density polyethylene (PE) sheets by corona discharge treatment with gradually increasing power and graft copolymerization of poly(ethylene glycol) monomethacrylate macromers (PEG-MA). Macromers with PEO chain lengths 1, 5, and 10 were used. The comb-like PEO gradient surfaces prepared were characterized by measurement of the water contact angle, Fourier transform infrared spectroscopy in the attenuated total reflectance mode (FTIR-ATR), and electron spectroscopy for chemical analysis (ESCA). The FTIR-ATR and ESCA measurements indicated that the PEO chains are grafted onto the PE surface with gradually increasing density of PEO. The gradient surfaces prepared can be used to systematically investigate the interactions of biological or other species in terms of PEO chain length and its surface density of polymeric materials.

Associations Between Hydrophibically End-Capped Polyethylene Oxide and Water Soluble (β Cyclodextrin Polymers

Abstract In this study, polyethylene oxide chains have been hydrophobically end-modified with naphthalene groups (PEO-N), and water soluble ß-cyclodextrin polymers (ß-CD/EP) have been synthesized. An original associating system can be obtained by mixing these two polymers in aqueous solutions. Inclusion complex formation between the hydrophobic moieties of the PEO-N chains and the ß-cyclodextrin cavities of the ß-CD/EP polymers are at the origin of the polymolecular associations. Fluorescence anisotropy measurements allowed the determination of the complexation constants, and the onset of the polymolecular associations have been monitored by viscosimetry. The PEO chain length influence has been studied by using two molecular weights, 6000 and 20000.

Adsorption of nonionic and cationic surfactants from aqueous binary mixtures onto the solid/liquid interface

The effect of the cationic surfactant cetyltrimethylammonium bromide (CTAB) on the adsorption of the nonionic surfactant iso-nonilphenol ethoxylate with an average polyethylene oxide chain length of about 25 at the limestone/solution interface was studied. The adsorption and effect of individual and mixed solutions of surfactants on the wetting behaviour of limestone surface was also studied. The results indicated that only CTAB was adsorbed onto the limestone surface from solutions of mixture surfactants. The results also showed that hydrophobization of the solid surface occurred at a very low concentration and then, as the concentration of surfactants increased it became hydrophilic.

Concentrated coal-water suspensions containing nonionic surfactants and polyelectrolytes 2. Adsorption of nonyl phenyl propylene oxide-ethylene oxide on coal and the rheology of the resulting suspension

Adsorption isotherms of a series of nonionic surfactants (Synperonic NPE) on coal showed a systematic decrease in the amount of adsorbed surfactant (Γ in μmol g −1) with increase in polyethylene oxide (PEO) chain length. A plot of Γ vs. n 1 2 (where n is the number of EO units) was linear indicating that the adsorbed amount is determined by the size of the PEO chain. Viscoelastic measurements on coal dispersions stabilized by these nonionic surfactants showed a rapid increase in the complex and storage moduli ( G ∗ and G′ respectively) at a critical volume fraction of coal, Φ cr. The latter was highest for the surfactant containing 48 EO units. The lower Φ cr obtained with the surfactant containing the shorter PEO chain (27 units) was due to the weak flocculation obtained with these dispersions. At longer PEO chains (79 and 174) desorption of the chains may occur and this results in greater flocculation. It was concluded that an optimum PEO chain length was required for maximum stability.

Behavior of Polyethylene Oxide Based Nonionic Surfactants in Silicon Processing Using Alkaline Solutions

The adsorption of polyethylene oxide (PEO) based nonionic surfactants onto hydrophobic silicon from an alkaline solution was investigated using an in situ attenuated total reflection Fourier transform infrared spectroscopy technique. The adsorption/desorption profiles of surfactants were affected by the type and length of the hydrophobic group and the lengths of hydrophilic PEO chains. Complete wetting of hydrophobic silicon was measured at surfactant concentrations in the range of 50 to 200 ppm. Surfactant adsorption was controlled by hydrophobic attractions between the hydrophobic moiety of surfactant and the silicon surface. The addition of surfactant to alkaline solutions dramatically reduced the etch rate of silicon and resulted in a smoother silicon surface. Oxidizing treatments followed by buffered oxide etching (BOE) were effective in the complete removal of adsorbed surfactant.

Addition of Block Copolymers to Liposomes Prepared Using Soybean Lecithin. Effects on Formation, Stability and the Specific Localization of the Incorporated Surfactants Investigated

Soybean lecithin disperses into water forming multilamellar liposomes, which on sonication produce vesicles of the order of 40–50nm (diameter), as determined by Photon Correlation Spectroscopy (PCS). The effect of concentration of lecithin and sonication time was systematically investigated. Vesicles were then prepared by incorporation of A – B – A block copolymers of polyethylene oxide (PEO) and polypropylene oxide(PPO), i.e.(PEO-PPO-PEO), in order to construct systems of increased steric stability. The effect of the molecular weight of the PEO and PPO chains on the vesicle size was systematically studied by using various molecules to prepare the vesicles. Initial addition of these (tri-)block copolymers causes an increase in the size of the vesicles. This increase continues until a certain concentration of block copolymer is reached, after which a decrease in size is observed. The initial increase was thought to be due to the incorporation of the block copolymer onto the vesicle bilayer. The reduction at high surfactant concentration is thought to be due to solubilization of the bilayer and the ultimate breakdown of the vesicles. Electrophoresis experiments showed a reduction in the ξ-potential of the vesicles on incorporation of the block copolymer which can be attributed to the shift of the shear plane. Various models are presented to describe this incorporation. The vesicles prepared using the block copolymers are believed to enhance the steric effects and so lead to more stable and pharmaceutically optimum systems.

Biocompatibility of Polysulfone I. Surface Modifications and Characterizations

Surface treatments by nonionic surfactant (Brij) coating and air-plasma glow discharge treatment onto polysulfone have been investigated to improve its surface properties. Surface treated samples were characterized by measurement of contact angle by a goniometer, Fourier transform infrared spectroscopy in the attenuated total reflectance mode (FTIR-ATR), and electron spectroscopy for chemical analysis (ESCA). The contact angles of the nonionic surfactant coated films decreased from 66.6 +/- 2.1 degrees to nearly 0 degrees due to hydrophilic polyethylene oxide (PEO) chain segment of the nonionic surfactant, and those of air-plasma treated films also decreased from 66.6 degrees to about 22 degrees with a treatment time of less than 5 s. ESCA analysis of air-plasma treated films indicates the incorporation of oxygen molecules onto polysulfone surface lowers the water contact angle. These modified techniques can be used to prevent platelet adhesion onto polysulfone surfaces.

Microstructure of polyurethane ionomers derivatized with dodecylamine and polyethylene oxide in the hard segment

AbstractSegmented polyether‐polyurethanes containing sulfonate groups in the hard segment were modified by the grafting of polyethylene oxide and C12 hydrocarbon chains. The grafts were attached via the sulfonate groups. The physical properties of the materials, including stress–strain behavior, thermal behavior, and water uptake were studied. Grafting was found to alter material behavior significantly. Both the alkyl and polyethylene oxide grafts appear to alter the packing of the hard segments in microdomains because the grafted materials, in contrast to their sulfonated precursor, do not exhibit a melting transition. However, the polyethylene oxide chains appear to interact with the hard segments, probably through hydrogen bonding. For the C12 grafted materials, differential scanning calorimetry showed that a third microphase, consisting largely of C12 chains, may be formed by annealing. Stress–strain and water uptake data support these interpretations. The grafted materials were found to absorb more water than the sulfonated precursor. Most of the water taken up by the C12 material appears to be bulk water whereas for the PEO materials the absorbed water behaves as if it is bound. © 1994 John Wiley & Sons, Inc.

In vitro phagocytosis assay of nano- and microparticles by chemiluminescence. IV. Effect of surface modification by coating of particles with poloxamine and Antarox CO on the phagocytic uptake

The in vitro phagocytosis of differently sized surface-modified polystyrene particles (85, 480, 1030 and 3190 nm) was studied in cultures of human granulocytes. Surface modification was performed by the adsorption of poloxamine polymers and Antarox surfactants (coating). Particle uptake was quantified by chemiluminescence (CL) measurements. In general, uptake decreased with increasing adsorption (coating) layer thickness, length of the polyethylene oxide chain in the molecule and surface hydrophilicity of coated particles for both poloxamine and Antarox. Antarox surfactants possessed a more hydrophobic anchor part (nonylphenol) for adsorption on the particle surface than poloxamine (polypropylene oxide) but proved less effective in reducing phagocytosis. This was attributed to the hydrophobicity of the Antarox coated particles. An observed distinct reduction in phagocytosis with low molecular weight Antarox possessing thin coating layers could be identified as an interaction of free surfactant with the granulocytes.

Adsorption of nonyl phenol propylene oxide—ethylene oxide surfactants on carbon black and the rheology of the resulting dispersions

The stability of concentrated aqueous dispersions of carbon black has been investigated using rheological measurements. The dispersions are stabilised by a series of Synperonic NPE non-ionic surfactants. These materials contain nonyl phenol, 13 units of propylene oxide and between 27 and 175 ethylene oxide units. The adsorption of the surfactants onto carbon black was studied. The adsorption isotherms revealed that the weight of surfactant adsorbing per unit area was approximately constant (or the number of molecules of surfactant adsorbing decreases with increase of the molecular weight of the polyethylene oxide chain). All the surfactants studied stabilised the carbon dispersions. However, those stabilised by the higher molecular weight surfactants showed higher viscosities and elastic moduli than those stabilised by the lower molecular weight materials. With these surfactants it was possible to prepare dispersions with a phase volume of carbon up to 55%. From the elastic and viscous properties of these dispersions it was possible to estimate the thickness of the adsorbed surfactant layer. This agreed closely with that obtained from light scattering. Critical flocculation temperature of the surfactant-stabilised dispersions corresponded to the 0 temperature of the polyethylene oxide, indicating that the mechanism for stabilisation of carbon black is steric in nature.

Concentrated coal—water suspensions containing non-ionic surfactants and polyelectrolytes 1. A preliminary study using rheology and adsorption isotherms

The influence of addition of dispersing agents on the properties of coal—water suspensions has been investigated using adsorption isotherms, and rheological (steady state and oscillatory techniques) measurements. Four different dispersants were investigated - two non-ionic ethoxylated surfactants and two anionic polyelectrolytes (lignosulphonate and naphthalene formaldehyde sulphonated condensates). The non-ionic dispersants showed an initial increase in the complex modulus and viscosity, with further decrease on ??? the dispersant concentration. The initial increase was attributed to adsorption of the non-ionic dispersant with the polyethylene oxide (PEO) chain partly directed towards the surface (probably by hydrogen bonding with polar groups such as CO and -COOH) leaving the hydrocarbon chain pointing towards the bulk solution. This makes the coal surface initially more hydrophobic resulting in its enhanced flocculation. On further addition of the non-ionic dispersant, adsorption occurs by hydrophobic bonding between the alkyl group and the hydrophobic portions of the coal surface. These result in a hydrophilic surface and the PEO chains provide steric stabilisation. With the anionic polyelectrolytes, adsorption occurs via the hydrophobic groups present on the chains leaving the charged chains dangling from the surface. This results in a combination of electrostatic and steric stabilisation. Adsorption isotherms showed good correlation with the rheological results, namely a rapid reduction in absolute shear modulus and viscosity at the concentration at which the steep rise in adsorption occurs. A comparison between the various dispersants was obtained from the complex modulus, | G*|, and viscosity, η pl volume fraction curves. The non-ionic dispersants showed a steep rise in | G*| and η pl at a critical volume fraction of coal that was lower than that obtained with the anionic polyelectrolyte. A more quantitative comparison was obtained from the maximum packing fraction φ p which could be calculated from the plot of | G*| −0.5 and η −0.5 pl vs φ c. The maximum packing fraction was higher with the anionic polyelectrolytes when compared with the non-ionic dispersants. However,

Redox behaviour of phthalocyanines bearing aliphatic and polyethylene oxide chains

Redox behaviour of phthalocyanines bearing aliphatic and polyethylene oxide chains

Redox behaviour of phthalocyanines bearing aliphatic and polyethylene oxide chains

The electrochemical behaviour of phthalocyanines octasubstituted by aliphatic and by polyethylene oxide chains has been studied. Monocation radicals were electrogenerated by oxidation, whereas the reduction produced monoanion radicals and dianions. The substituents have limited effects on the oxidation/reduction potentials of the phthalocyanines. However, the eight C 12 aliphatic chains in C 12PcM significantly decrease the rate constant of the first reduction. Another result of the substitutions is enhancement of the surface-active properties of the phthalocyanines, thus triggering a strong adsorption of these molecules on the electrodes.

Protein—surface interactions in the presence of polyethylene oxide: I. Simplified theory

The protein resistance character of polyethylene oxide (PEO) chains terminally attached to a hydrophobic solid substrate is theoretically studied. Steric repulsion, van der Waals attraction, and hydrophobic interaction free energies are considered. The results are dependent on the chain length and surface density of PEO. The protein approaches the PEO surface by diffusion and is affected by the van der Waals attraction between the PEO surface and protein through water. Further approach of the protein initiates the compression of PEO chains, which induces a steric repulsion effect; an additional van der Waals attraction becomes important between the substrate and protein through the water solvated PEO layer. The van der Waals component with the substrate decreases with increasing surface density and chain length of terminally attached PEO chains. Other synthetic polymers were also studied, indicating that the protein resistance character is related to the refractive index, with PEO having the lowest refractive index of the common water-soluble synthetic polymers. The osmotic and elastic constants of steric repulsion for terminally attached PEO were estimated as ∼0.007 and 0.02, respectively, from literature data for PEO adsorbed to mica. The steric repulsion free energy and the combined steric repulsion and hydrophobic interaction free energies were calculated as a function of surface density and chain length of PEO. The free energy calculations as a function of surface density and chain length of PEO reveal that a high surface density and long chain length of terminally attached PEO should exhibit optimal protein resistance, with the attainment of high surface density of PEO being more important than long chain length. These theoretical results should be helpful in the design and development of materials resistant to protein adsorption.

Protein—surface interactions in the presence of polyethylene oxide: II. Effect of protein size

Polyethylene oxide (PEO) surfaces exhibit low protein adsorption. PEO surface—protein interactions are examined theoretically as a function of surface density and chain length of PEO and variation in the size of the protein (assumed to be a sphere). Recent studies suggest that the PEO surface may have a small hydrophobic character. We study the effect of surface density of PEO and protein size and deduce the PEO surface density conditions for optimal protein resistance. For small proteins ( R ∼ 20 A ̊ ), D should be small (∼ 10 Å), while for large proteins ( R ∼ 60–80 A ̊ ), D should be larger (∼ 15 Å), where R is the protein radius and D is the average distance between end-attached PEO chains. These results evolve from the trade-offs between steric repulsion and the assumed weak hydrophobic interaction between the PEO layer and the protein. The longest chain length of PEO at optimum surface density appears best for protein resistance. As a number of assumptions and estimates are involved in the model, the results can be taken only as qualitative trends at this time. The trends should be helpful in the design and evaluation of surfaces resistant to protein adsorption.

A NEW METHOD TO PREPARE UNIFORM PARTICLES; PRECIPITATION FROM LYOTROPIC LIQUID CRYSTALS

ABSTRACT Basic copper sulfate panicles of uniform size and shape were prepared at room temperature by precipitation from a lyotropic liquid crystal of water and Tween 80, a nonionic surfactant. The size (< 2.5 μm) of the panicles depended on the pH of the aqueous copper salt solution and the precipitation time. The formation of the basic precipitates at room temperature was due to the presence of polyethylene oxide chains in the aqueous layers, while the narrow size distribution was due to immobilization of panicle nuclei by the rigidity of the liquid crystal.

Adsorption of ethoxylated surfactants on nanoparticles. I. Characterization by hydrophobic interaction chromatography

Hydrophobic interaction chromatography (HIC) was employed to assess the surface hydrophobicity of model drug carriers (polystyrene particles) after surface modification by adsorption of ethoxylated surfactants (coating). The hydrophobicity of Poloxamer and Poloxamine 908 coated particles decreased with increasing polyethylene oxide chain length and increasing thickness of the coating layer. A reversed effect was observed for ethoxylated nonylphenols. Particles coated with Antarox CO 660 containing 10 moles ethylene oxide were least hydrophobic despite forming the thinnest coating layer. The Antarox results elucidate the contribution of the polymer solvency and affinity to the surface to the properties of the adsorption film. In conclusion, altering the hydrophobic and hydrophilic part of the surfactant molecule can be used to adjust solvency and affinity to form optimised coating layers with low hydrophobicity.