Poly Ethylene Oxide Block Copolymers Research Articles

Polyethylene oxide-polypropylene oxide -polyethylene oxide derived porous carbon materials with different molecular weights as ORR catalyst in alkaline electrolytes

Polyethylene oxide (PEO)-polypropylene oxide (PPO)-polyethylene oxide block copolymer having different molecular weights are used as precursors of carbon materials to prepare Hollow -Derivatives carbon material as an electrocatalyst through block copolymer self-assembly. The composition and microstructure of the prepared catalysts are shown by Raman spectroscopy, X-ray diffraction (XRD), Test of nitrogen adsorption and desorption curves, High resolution transmission electron microscopy (HR-TEM) and scanning electron microscopy (HR-SEM). Oxygen was passed into alkaline electrolyte solution until the solution reached saturation state. With molecular weight increasing, the obtained sample gradually changed from block to hollow and spherical. When the molecular weight was 12600 g mol−1, the evenly hollow carbon nanocages was acquired (C-12600). In O2 saturated alkaline electrolyte (0.1 M KOH solution), C-12600's limited current density，half-wave potential and initial potential are 5.23 mA cm−2@0.4 V, 0.72 V and 0.81 V, respectively. And most important is that half-wave potential and onset potential have barely change after 2000 cycles of cyclic voltammetry. As a result, the porous carbon materials exhibited excellent electrocatalytic activity while maintaining high stability in alkaline KOH solution.

Resolution of water in crude oil emulsion by some novel aromatic amine polyesters

In this work, three aromatic amines (p-toluidine, p-nitroaniline and p-chloroaniline) were chosen as bases for the repatriation of some nonionic polyesters. These amines were ethoxylated with different total number of ethylene oxide units 6, 12, 18. The prepared ethoxylated amine diols were polyesterified with maleic anhydride and polypropylene oxide polyethylene oxide block copolymers in polyesterification reaction. The demulsification efficiency of these demulsifiers was investigated using the bottle test. The effects of the molecular weight, concentration, asphaltene content, water content, Hydrophile Lipophile Balance (HLB) and temperature on the demulsification efficiency were investigated. The surface active properties were correlated with their demulsification efficiency. It was found that, NAE18D gave the best result in the demulsification process. The demulsification efficiency was discussed on the light of surface active properties, interfacial tension and the factors affecting the demulsification. The surface-active properties of the prepared demulsifiers were measured at 60°C.

Effect of cosolvents on the self-assembly of a non-ionic polyethylene oxide–polypropylene oxide–polyethylene oxide block copolymer in the protic ionic liquid ethylammonium nitrate

The effect of water and methanol on the self-assembled structures formed by the polyethylene oxide–polypropylene oxide–polyethylene oxide block copolymer Pluronic P123 in ethylammonium nitrate was investigated by small angle X-ray scattering (SAXS). Two ternary phase diagrams were established. The addition of water had only a minor effect on the liquid crystal structures, however methanol had a significant effect, which was attributed to methanol being a good solvent for both the PEO and PPO blocks of the polymer. No lyotropic liquid crystal phases were retained when methanol reached 25wt%. The phase behaviour did not change significantly over the temperature range from 25 to 45°C.

Interaction of Curcumin with PEO–PPO–PEO Block Copolymers: A Molecular Dynamics Study

Curcumin, a naturally occurring drug molecule, has been extensively investigated for its various potential usages in medicine. Its water insolubility and high metabolism rate require the use of drug delivery systems to make it effective in the human body. Among various types of nanocarriers, block copolymer based ones are the most effective. These polymers are broadly used as drug-delivery systems, but the nature of this process is poorly understood. In this paper, we propose a molecular dynamics simulation study of the interaction of Curcumin with block copolymer based on polyethylene oxide (PEO) and polypropylene oxide (PPO). The study has been conducted considering the smallest PEO and PPO oligomers and multiple chains of the block copolymer Pluronic P85. Our study shows that the more hydrophobic 1,2-dimethoxypropane (DMP) molecules and PPO block preferentially coat the Curcumin molecule. In the case of the Pluronic P85, simulation shows formation of a drug-polymer aggregate within 50 ns. This process leaves exposed the PEO part of the polymers, resulting in better solvation and stability of the drug in water.

Solubilization and Release of a Model Drug Nimesulide from PEO–PPO–PEO Block Copolymer Core–Shell Micelles: Effect of Size of PEO Blocks

The commercially available polypropylene oxide (PPO)–polyethylene oxide (PEO) symmetrical triblock copolymers (Pluronics®) have been recognized as pharmaceutical excipients and used in a variety of applications. This paper reports studies on micellar and solubilization behavior of three PEO–PPO–PEO block copolymers, viz. P103, P104 and P105 (same PPO mol. wt = 3250 g·mol−1 but different % PEO = 30, 40 and 50 %, respectively) in aqueous solutions. Critical micellization concentrations (CMCs), critical micellization temperatures (CMTs), and micelle size/polydispersity for copolymers with and without the drug, nimesulide (NIM), are reported. The solubilization of NIM is significantly enhanced with increasing hydrophobicity (P103 > P104 > P105), concentration, temperature and in the presence of added salt. The copolymer hydrophobicity, temperature and the drug loading strongly affect micelle behavior. The micelle–water partition coefficient (P) and thermodynamic parameters of solubilization, viz. Gibbs energy (\( \Updelta G_{s}^{\text{o}} \)), enthalpy (\( \Updelta H_{s}^{\text{o}} \)) and entropy (\( T\Updelta S_{s}^{\text{o}} \)), were calculated. The solubilization site of the drug in different micellar solutions and its release from Pluronics® micelles in phosphate buffer saline (PBS) solution at 37 °C were examined. The kinetics of NIM exhibits burst release characteristics, which are believed to be controlled by degradation of the copolymers. These studies were carried out to investigate the feasibility of using Pluronics® as a release vehicle of nimesulide in vitro. From the results, it was concluded that Pluronic® based formulations might be practical for drug delivery.

Two-dimensional liquid chromatography of polystyrene–polyethylene oxide block copolymers

In this study, liquid chromatography at critical conditions of polystyrene (PS) and polyethylene oxide (PEO) is used as the first dimension for the two-dimensional analysis of PS-b-PEO copolymers. Comprehensive two-dimensional liquid chromatography, with size exclusion chromatography as the second dimension, reveals information about the molar mass distributions of all separated fractions from the first dimension. Furthermore, fractions eluting at the critical conditions of one block were collected and subjected to analysis in the second dimension at the critical conditions of the other block. These fractions were analysed by FTIR to determine their chemical compositions. The combination of the above approaches and the calibration of the evaporative light scattering (ELS) detector for the first-dimensional analysis yield deep insights into the molecular heterogeneity of the block copolymer samples. The composition of the samples and the chemical composition of the real block copolymer are also calculated by combining results obtained at both critical conditions.

Nonfouling biomaterials based on polyethylene oxide‐containing amphiphilic triblock copolymers as surface modifying additives: Synthesis and characterization of copolymers and surface properties of copolymer–polyurethane blends

AbstractThe objective of this work is to develop nonfouling biomaterials by blending polyethylene oxide (PEO)‐containing block copolymers with a polyurethane (PU) matrix; it is expected that the PEO component will migrate to the tissue‐material interface. Three amphiphilic triblock copolymers, PEO‐PU‐PEO, in which the PEO MW was 550 (copolymer 1), 2000 (copolymer 2), and 5000 (copolymer 3), respectively, were synthesized. XPS data showed that the polymer/vacuum interfaces of copolymers 2 and 3 were enriched in the PU block, whereas that of copolymer 1 was enriched in the PEO block. In contact with water, the PEO blocks for all three copolymers migrated to the surface as indicated by water contact angles. Blends of the copolymers with a segmented polyurethane were investigated. Surface enrichment of the copolymers occurred and increased over time up to a limit; the degree of enrichment was dependent on PEO block size and copolymer content. At copolymer content <10%, enrichment decreased with increasing PEO block size. For the copolymer 2 and copolymer 3 blends, enrichment increased with increasing copolymer content; at 20% copolymer the surfaces consisted essentially of pure copolymer. For the copolymer 1 blends, the surface was completely covered by copolymer at content ≥ 1%. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Morphology of PI–PEO block copolymers for lithium batteries

Polyimide (PI)–polyethylene oxide (PEO) block copolymers have a wide variety of applications in microelectronics, since PI–PEO films exhibit a high degree of thermal and chemical stability. The polymers consist of short, rigid rod T-shaped PI segments, alternating with flexible, PEO coil segments. The highly incompatible PI rods and PEO coils should phase-separate, especially in the presence of lithium ions used as electrolytes for lithium polymer batteries. The rigid rod phase provides a high degree of dimensional stability. In this paper, we provide evidence by DSC that the self-assembled ordered structure of the PI–PEO molecules is formed from concentrated solution rather than the bulk state. Tapping mode AFM and X-ray diffraction are applied to observe the nanodomains in the phase separation of the PI and PEO before and after doping with lithium ions. In addition, we report evidence of the ion transport primary mechanism, in the amorphous phase of the lithium salt-doped PI–PEO block copolymers' multinuclear NMR linewidth, spin-lattice relaxation time, and pulsed field gradient diffusion measurements.

Monolayer formation of PBLG–PEO block copolymers at the air–water interface

Physicochemical properties of PBLG (poly( γ-benzyl- l-glutamate))–PEO (poly(ethylene oxide)) diblock copolymers composed of PBLG as the hydrophobic rod component and PEO as the hydrophilic component were investigated at the air–water interface. Surface pressure–area isotherms obtained by the Wilhelmy plate method provide several variables such as molecular size, compressibility of PEO, and the free energy change of the PBLG–PEO block copolymer. GE-1 ( M w of PBLG:PEO = 103,700:12,000 ), with a relatively longer rod, has negative temperature effects and GE-3 ( M w of PBLG:PEO = 8400:12,000 ), with a relatively shorter rod, shows a positive temperature effect because of the large entropy loss. These competitions were based on the block size of PBLG and PEO and were affected by various microstructures of the PBLG–PEO diblock copolymer. Monolayer aggregations transferred onto mica from the air–water interface were analyzed with AFM. AFM images of GE-1 monolayers show cylindrical micelles, but the self-assembled structure has many large domains. The monolayer of GE-2 ( M w of PBLG:PEO = 39,800:12,000 ), which has a medium size rod, forms a spherical structure at the air–water interface. Monolayers of GE-3, with a short rod length, form bilayer structures. These results demonstrate that the microstructures of PBLG–PEO diblock copolymers are related to free energy changes between rod and coil blocks.

Synthesis and Surface Tension Properties of Polyethyleneimine‐ Polyethylene Oxide Block Copolymers

AbstractThis paper describes the synthesis, surface tension and dispersancy properties of block copolymer nonionic surfactants comprised of polyethyleneimine (PEI) and polyethylene oxide (PEO) blocks of selected lengths. These block copolymers were prepared by a threestep synthetic sequence. Firstly, PEO glycol was converted to its dimethanesulphonylester (dimesyl) derivative by reacting with methanesulphonyl chloride. Then a tri‐block polymer was prepared by the ring‐opening polymerization of 2‐methyl‐2‐oxazoline (MeO‐ZO) with the dimesyl PEO derivative. Lastly, linear PEI blocks were obtained by subsequent hydrolysis and purification. 1H NMR spectra confirmed the structures of the intermediate, final products and their purities (> 99%). The utility of these block copolymers is described in terms of their surface tension and day dispersancy measurements as a function of copolymer chain and block length.

Mixed Micelles of Triton X‐100 and Sodium Dodecyl Sulfate and Their Interaction with Polymers

Micellization of polyoxyethylene tert‐octylphenyl ether, Triton X‐100 [TX‐100], and sodium dodecyl sulfate [SDS] and their mixtures at varying mole fraction was investigated by surface tension measurements at 30°C. Changes in the critical micelle concentration (CMC) with the composition of the two surfactants so determined were analyzed by applying the Rubingh's regular solution theory to obtain interaction parameter, β ( = −3.81) showing synergism. Sodium dodecyl sulfate shows a remarkable interaction with polyethylene oxide [PEO, mol. wt. = 6000] and polyethylene oxide–polypropylene oxide–polyethylene oxide block copolymer [P65: EO19PO30EO19, total mol. wt. = 3400, % EO = 50], while no such interaction was observed for TX‐100. Interaction weakens in mixed micelle and diminishes when the mole fraction of TX‐100 in mixed system increases. Turbidimetric studies show that the presence of TX‐100 in SDS improves calcium ion tolerance.

Surface activity of poloxamines at the interfaces between air–water and hexane–water

Abstract Poloxamines are tetra functional block copolymers, which contain four polyethylene oxide (PEO)–polypropylene oxide (PPO) chains joined to a central ethylene diamine moiety by way of the nitrogen atoms. Surface and interfacial tensions at the air–water and hexane–water interfaces have been determined over a wide concentration range for several of these block copolymeric amphiphiles. Titration data indicates that these molecules are dibasic. Two pKa values—corresponding to proton loss from the central nitrogen atoms of the molecule—have been determined by fitting titrimetric data to a thermodynamic model of the titration process. The values obtained are fairly constant for different poloxamines, which suggests that varying the block size has little impact upon these pKa values. However, the values obtained are lower than those observed for ethylene diamine and indicate that the attachment of the PEO–PPO chains to the nitrogen atoms does reduce their basicity. The Gibbs adsorption isotherm at the air–water interface is similar to the adsorption pattern reported for the poloxamers-linear PEO–PPO–PEO block copolymers [Langmuir 10 (1994) 2604] and shows that the highly branched poloxamines have similar interfacial properties as the poloxamers. Data is also reported on adsorption of poloxamines at the hexane–water interface. In the main it is concluded that those block copolymers with high PPO to PEO ratios and which are, therefore, relatively hydrophobic are more effective in reducing surface and interfacial tensions. These effects are, however, attenuated by changes in aqueous phase pH, which alters the charged nature of the poloxamine molecule.

SANS study of salt induced micellization in PEO–PPO–PEO block copolymers

Small-angle neutron scattering (SANS) measurements have been carried out from the aqueous solutions of polyethylene oxide (PEO)–polypropylene oxide (PPO)–PEO block copolymers of pluronics F88 and P84 in presence of salt KCl. It is seen that the effect of addition of salt is similar to that of increasing temperature. The pluronics exist as unimers at low temperatures and their micellization takes place when the salt is added or the temperature is increased. The measurements for different salts of the lyotropic series on the above pluronic systems show that micellar structure is sensitive to the sizes of the hydrated ions of these salts.

Organisation and interactions in aqueous dispersions of polystyrene–polyethylene oxide block copolymer micelles

Diblock copolymers of polystyrene (PS) and polyethylene oxide (PEO) with a total molecular weight of circa 7500gmol−1 and a PS weight fraction of circa 0.15 have been synthesised in all possible variants of hydrogenous and deuterated forms. The copolymers have been dispersed at concentration above the critical micelle concentration (cmc) in aqueous dispersion mediums of varying contents of light and heavy water to contrast match selected components of the micelles. Small angle neutron scattering has been used to determine the size of the micelles, the radius of the PS core and the thickness of the PEO corona using data for dispersions with concentrations less than or equal to 1×10−2gml−1. At higher concentrations, a structure factor peak becomes increasingly evident as the concentration increases to 6.5×10−2gml−1. The total scattering could not be fitted using the structure factor for an assembly of hard spheres; a structure factor originally developed for coulombically stabilised micelles was used and excellent fits to the data obtained. The structure factor is described in terms of a Yukawa potential between the micelles and the values of the repulsion potentials have been used to calculate the repulsive force between the micelles and compared to the predictions for two brush-like polymer layers approaching each other. There is partial agreement with the model, the disagreement being identical to that observed when the results from force balance experiments are compared with the model.

Effect of Polyethylene Oxide Blocks or Grafts on the Physicochemical Properties of Poly(2-N-(Dimethylaminoethyl) Methacrylate) DNA Complexes

The synthesis and the physicochemical evaluation of a series of polyethylene oxide (PEO) containing polyamines are described as potential vectors in gene therapy. Two different types of vectors were synthesized: PEO block copolymers and copolymers containing PEO grafts. The building unit of the polyamine is 2-N-(dimethylaminoethyl) methacrylate. All polymers are able to condense DNA according to dynamic light scattering measurements and ethidium bromide exclusion tests. Complexes of PEO block copolymers and DNA show a stability comparable to that of the homopolymer poly(2-N-(dimethylaminoethyl) methacrylate) (PDMAEMA). Polymers with a PEO graft show a lower stability compared to the unmodified polymer. Incorporation of a PEO graft resulted in a decrease in the zeta potential of the complexes at all charge ratios. The interaction of a serum albumin with complexes of DNA and PEO containing polymers was studied at different protein concentrations. Polymers with a PEO graft show a lower interaction with serum albumin compared to the homopolymer based on turbidity measurements.

SPR analysis of the total reduction of protein adsorption to surfaces coated with mixtures of long- and short-chain polyethylene oxide block copolymers

PEO/PPO/PEO triblock copolymers have previously been shown to reduce the binding of proteins to a variety of surfaces. In this study, mixtures of long- and short-chain copolymers have been shown to adhere to gold substrate surface plasmon resonance slides. The mixtures have been shown to significantly reduce the binding of BSA to gold surfaces, compared to the more commonly used long chain PEO copolymers. These mixtures have been shown to be more effective, than either short, or long-chain copolymers used individually, complementing a published theoretical treatise of PEO surfactant behaviour towards protein interaction with surfaces.

Micellar enhanced ultrafiltration using PEO–PPO–PEO block copolymers

The solubilization characteristics of PEO–PPO–PEO (polyethyleneoxide–polypropyleneoxide–polyethyleneoxide) block copolymers for aqueous solutions containing 1-naphthol and phenol, respectively, were investigated to examine their possibility of use as new surfactants for forming micelles in MEUF (micellar enhanced ultrafiltration). The optimum conditions for MEUF process to remove the solutes such as 1-naphthol and phenol from wastewater were examined. A method for regeneration and recycling of the polymer used in the separation of solutes in MEUF was proposed based on the concept of micellar temperature range and found to be very effective.

Effect of the Steric Stabilizing Layer on the Phase Behavior and Rheology of Small Polystyrene Latex Dispersions Induced by Changes to the Concentration of Nonadsorbing Hydroxyethylcellulose

In this paper the influence of the adsorbed PEO−PPO−PEO (PEO, poly(ethylene oxide); PPO (poly(propylene oxide)) stabilizing polymer on latices is studied. Experiments are presented for small, 67 nm, polystyrene latex with either Synperonic PE/P103, P105, or F108 PEO−PPO−PEO block copolymers adsorbed onto the latex surface at full coverage. Nonadsorbing hydroxyethylcellulose (300 000 molar mass) has been added as the depleting polymer to flocculate the particles, which are at a core volume fraction of 0.159. Rheology, sedimentation, and microscopy have been used to characterize these suspensions. As the polymer concentration is increased, phase separation is noted. Firstly a gas−liquid phase transition is noted and viscoelastic gels are formed. Further increase in polymer concentration results in three phases: gas, liquid, and solid being in thermodynamic equilibrium. At yet higher concentrations a solid−gas phase transition is noted. It was further noted that the polymer concentration required to bring about these changes increased as the stabilizing chain length decreased. Oscillatory shear measurements showed that identical floc structures were formed with each of the stabilizing polymers while yield stress measurements revealed stronger flocculation with the higher molecular weight stabilizers, in accord with the observed phase behavior. These observations are a result of softer interactions with the suspensions bearing the shorter molecular weight chains. The experimental yield stress values are compared with the VEEJ (Vincent, Edwards, Emmett, Jones) theory for the depletion interaction of soft spheres.

Nonaqueous drug permeation through synthetic membranes

Drug permeation through membranes in nonaqueous systems was studied as a model for understanding drug delivery systems utilizing nonaqueous media. Solute permeation rates through membranes can be affected by a variety of factors including medium viscosity, membrane swelling and the molecular size of the solute. The effects of these factors on membrane permeation of drugs were investigated. A poly(propylene oxide)/polyethylene oxide block copolymer membrane was synthesized for this study. The nonaqueous media used in the permeation studies exhibited a wide range of viscosity and also resulted in varying degrees of membrane swelling. Binary mixtures of the selected media permitted independent control over both viscosity and membrane swelling. Drugs exhibited exponentially decreasing permeabilities as medium viscosity increased, with the magnitude of the decrease dependent upon membrane swelling. Also, the dependence of permeability on membrane swelling was larger in more viscous media. Permeation experiments using model ionic drugs of different molecular sizes demonstrated a strict size dependence of permeability in water, which suggested a pore mechanism for ion permeation. In contrast, for permeation in a nonaqueous medium, an additional partition mechanism was found to be responsible for the observed deviation from linear size dependence. This is attributed to the formation of electrically neutral and lipophilic ion pairs.