Low Molecular Weight Polyethylene Oxide Research Articles

Formability of low-molecular weight polyethylene oxide reinforced by tempo-oxidized nanocellulose for lithium-ion battery solid polymer electrolyte

Formability of low-molecular weight polyethylene oxide reinforced by tempo-oxidized nanocellulose for lithium-ion battery solid polymer electrolyte

Bio-Resorption Control of Magnesium Alloy AZ31 Coated with High and Low Molecular Weight Polyethylene Oxide (PEO) Hydrogels.

Magnesium AZ31 alloy has been chosen as bio-resorbable temporary prosthetic implants to investigate the degradation processes in a simulating body fluid (SBF) of the bare metal and the ones coated with low and high-molecular-weight PEO hydrogels. Hydrogel coatings are proposed to control the bioresorption rate of AZ31 alloy. The alloy was preliminary hydrothermally treated to form a magnesium hydroxide layer. 2 mm discs were used in bioresorption tests. Scanning electron microscopy was used to characterize the surface morphology of the hydrothermally treated and PEO-coated magnesium alloy surfaces. The variation of pH and the mass of Mg2+ ions present in the SBF corroding medium have been monitored for 15 days. Corrosion current densities (Icorr) and corrosion potentials (Ecorr) were evaluated from potentiodynamic polarisation tests on the samples exposed to the SBF solution. Kinetics of cumulative Mg ions mass released in the corroding solution have been evaluated regarding cations diffusion and mass transport parameters. The initial corrosion rates for the H- and L-Mw PEO-coated specimens were similar (0.95 ± 0.12 and 1.82 ± 0.52 mg/cm2day, respectively) and almost 4 to 5 times slower than that of the uncoated system (6.08 mg/cm2day). Results showed that the highly swollen PEO hydrogel coatings may extend into the bulk solution, protecting the coated metal and efficiently controlling the degradation rate of magnesium alloys. These findings focus more research effort on investigating such systems as tunable bioresorbable prosthetic materials providing idoneous environments to support cells and bone tissue repair.

Preparation and characterization of salicylic acid grafted chitosan electrospun fibers

Chitosan (chi) and its modified forms as electrospun nanofibers have potential applications in advanced water treatment and biomedicine. Polyethylene oxide (PEO) is an additive commonly used to facilitate the formation of chitosan electrospun fibers because PEO (Mw ≥ 400 kDa) affords chain entanglement that stabilize the electrospinning jet, leading to enhanced formation of chi-based electrospun fibers. Herein, we report on the preparation of chitosan grafted with salicylic acid and its utility to afford improved electrospun fibers with low molecular weight (LMw) PEO (Mw » 100 kDa). A comparison of the interactions between original and grafted chitosan with PEO reveals that stable supramolecular assemblies are established between grafted chitosan and PEO, which provides support that such supramolecular interactions favor formation of chitosan electrospun fibers. Moreover, a porous chitosan electrospun nanofiber was prepared through physical treatment that reveals notably higher (ca. 4-fold) dye uptake than the pristine (unmodified) chitosan electrospun nanofibers.

Electrospinning of Chitosan Biopolymer and Polyethylene Oxide Blends

Abstract The objective of this study is to investigate the morphological (scanning electron microscopicy images), thermal (differential scanning calorimetry), and electrical (conductivity) properties and to carry out compositional analysis (Fourier-transform infrared) of produced nonwoven fibrous materials adapted in biomedical applications as scaffolds. The orientation of produced nanofilaments was also investigated because it is considered as one of the essential features of a perfect tissue scaffold. Viscosity and electrical conductivity of solutions, used in the manufacturing process, were also disassembled because these properties highly influence the morphological properties of produced nanofibers. The nanofibrous scaffolds were fabricated via conventional electrospinning technique from biopolymer, synthetic polymer, and their blends. The chitosan (CS) was chosen as biopolymer and polyethylene oxide (PEO) of low molecular weight as synthetic polymer. Solutions from pure CS were unspinnable: beads instead of nanofibers were formed via spinning. The fabrication of pure PEO nanomats from solutions of 10 wt%, 15 wt%, and 20 wt% concentrations (in distilled water) turned out to be successful. The blending of composed CS solutions with PEO ones in ratios of 1:1 optimized the parameters of electrospinning process and provided the opportunity to fabricate CS/PEO blends nanofibers. The concentration of acetic acid (AA) used to dissolve CS finely spuninned the nanofibers from blended solutions and influenced the rate of crystallization of manufactured fiber mats. The concentration of PEO in solutions as well as viscosity of solutions also influenced the diameter and orientation of formed nanofibers. The beadless, highly oriented, and defect-free nanofibers from CS/PEO solutions with the highest concentration of PEO were successfully electrospinned. By varying the concentrations of AA and low molecular weight PEO, it is possible to fabricate beadless and highly oriented nanofiber scaffolds, which freely can found a place in medical applications.

Polyethylene Oxide (PEO) Molecular Weight Effects on Abuse-Deterrent Properties of Matrix Tablets.

While polyethylene oxide (PEO)-based matrix tablets are frequently used as abuse-deterrent dosage forms, there is limited information available regarding how the selection of formulation components and manufacturing processes affect the resulting abuse-deterrent properties. The objective of the current study was to evaluate the effects of formulation and process variables on the abuse-deterrent features of PEO-containing tablets. Directly compressed tablets were prepared using three different PEO molecular weights (100,000; 900,000; and 5,000,000). As anticipated, sintering/thermal treatment above the melting point of PEO was crucial to impart crush-resistant features (tablet hardness > 500N). In addition to the sintering temperature, the weight fraction of PEO in the tablets affected their mechanical strength, and at least 50% w/w PEO was required to impart the desired crush-resistant features. In addition, the formulation and process variables also impacted syringeability and injectability of the PEO gels formed when the tablets were hydrated to simulate attempted drug extraction. High molecular weight PEO (900,000 and 5,000,000) produced gels more resistant to syringeability and injectability compared to low molecular weight PEO (100,000). Sintering above the polymer melting point decreased PEO crystallinity after cooling, and longer sintering times resulted in PEO degradation producing lower viscosity gels with reduced resistance to syringeability and injectability. Although sintering above the melting point of PEO imparts optimal mechanical strength to the tablets, prolonged sintering durations negatively impact polymer stability and alter the resulting abuse-deterrent features of the PEO-based tablet formulations.

Influence of Chitosan Molecular Weight and Poly(ethylene oxide): Chitosan Proportion on Fabrication of Chitosan Based Electrospun Nanofibers

Fabrication of electrospun chitosan nanofibers is still a controversial issue in publications. Although regarding the lots of reports, mixtures of chitosan with a hydrophilic synthetic polymer such as polyethylene oxide (PEO) have been electrospun successfully, abundance of partly contradictory protocols in which one variable has been surveyed in each study is unfortunately baffling. In the present study, influence of three considerable parameters including the average molecular weight of chitosan, chitosan solution concentration and the mass ratio of polyethylene oxide to chitosan at the mixtures on electrospinning possibility as well as the quality of as-spun fibers is investigated. Eventually, the necessities for obtaining the best results are introduced followed by further analysis of optimized nanofibers using atomic force microscopy. According to our results, the blend solutions prepared from the low molecular weight (LMW) chitosan and PEO are efficient for reproducible production of bead-free electrospun nanofibers even in low proportion of polyethylene oxide.

The influence of modification of elastomer compositions in polyethylene oxides on their resistance to mineral oils

The influence of modifying of elastomer compositions based on nitrile rubber in the medium of low molecular weight polyethylene oxide on resistance of rubbers to liquid aggressive mediawas studied. Standard hydrocarbon oils – oil ASTM №1 and ASTM №3, having a constant chemical composition and properties, were used as aggressive fluids. Resistance of elastomer compositions to standard oil was evaluated by change in weight, volume and relative compression set after keeping the samples in these oils at elevated temperatures. The influence of aggressive environment on the degree of swelling and the value of compression set of compositions modified in polyethylene oxides medium was established. It has been shown that the mass/volume of modified rubbers during aging in oil ASTM №1 reduced to a lesser degree compared to unmodified samples, which is probably due to the influence of low molecular weight polyethylene oxides for the formation of vulcanizates structure. At the same time exposure to oil ASTM №3 of elastomer compositions increases the degree of swelling of modified rubber more than unmodified, which can be due to destruction by the action of aggressive medium additional intermolecular bonds between macromolecules of polyethylene oxide and rubber, resulting in increased flexibility of the elastomeric matrix segments. It revealed that modification of rubbers in low molecular weightpolyethylene oxides facilitates preparation of rubber with low compression set after aging in standard oils at elevated temperatures.

Formulation, in vitro evaluation and study of variables on tri-layered gastro-retentive delivery system of diltiazem HCl

Context: Tri-layered floating tablets using only one grade of polyethylene oxide (PEO) would enable easy manufacturing, reproducibility and controlled release for highly soluble drugs.Objective: To evaluate the potential of PEO as a sole polymer for the controlled release and to study the effect of formulation variables on release and gastric retention of highly soluble Diltiazem hydrochloride (DTZ).Methods: Tablets were compressed with middle layer consisting of drug and polymer while outer layers consisted of polymer with sodium bicarbonate. Design of formulation to obtain 12 h, zero-order release and rapid floatation was done by varying the grades, quantity of PEO and sodium bicarbonate. Dissolution data were fitted in drug release models and swelling/erosion studies were undertaken to verify the drug release mechanism. Effect of formulation variables and tablet surface morphology using scanning electron microscopy were studied.Results and discussion: The optimized formula passed the criteria of USP dissolution test I and exhibited floating lag-time of 3–4 min. Drug release was faster from low molecular weight (MW) PEO as compared to high MW. With an increase in the amount of sodium bicarbonate, faster buoyancy was achieved due to the increased CO2 gas formation. Drug release followed zero-order and gave a good fit to the Korsmeyer–Peppas model, which suggested that drug release was due to diffusion through polymer swelling.Conclusion: Zero-order, controlled release profile with the desired buoyancy can be achieved by using optimum formula quantities of sodium bicarbonate and polymer. The tri-layered system shows promising delivery of DTZ, and possibly other water-soluble drugs.

Rheology and Microstructure of Polymer Nanocomposite Melts: Variation of Polymer Segment−Surface Interaction

We have studied the effects of particle packing fraction, polymer molecular weight (MW), and polymer-segment-particle-surface affinity on the phase behavior of 44 nm silica dispersions in unentangled, low MW polyethylene oxide (PEO), polyethylene oxide dimethyl ether (PEODME), and polytetrahydrofuran (PTHF) through rheological measurement and small-angle X-ray scattering. Particles are shown to be stable in PEO nanocomposites up to high volume fractions due to an adsorbed layer of polymer segments that stabilizes particles in the melt. Comparison of the PEO nanocomposite to PEODME and PTHF nanocomposites reveals little evidence of an adsorbed layer in the spirit of the PEO nanocomposite. Measurement of the PTHF nanocomposite viscosity reveals evidence of segment slip at the particle surface by the particle intrinsic viscosity being less than Einstein's value. At higher particle volume fractions, the viscosity diverges, yielding an elastic response. The elastic response of the PEO nanocomposite has the signatures of a colloidal glass, while the PEODME and PTHF nanocomposites resemble a gel. Measurement of the particle structure factor reveals a change from overall repulsive particles in PEO to attractive particles in PTHF as the segment-surface interaction is changed.

A Coarse-Grained Model for Polyethylene Oxide and Polyethylene Glycol: Conformation and Hydrodynamics

A coarse-grained (CG) model for polyethylene oxide (PEO) and polyethylene glycol (PEG) developed within the framework of the MARTINI CG force field (FF) using the distributions of bonds, angles, and dihedrals from the CHARMM all-atom FF is presented. Densities of neat low molecular weight PEO agree with experiment, and the radius of gyration R(g) = 19.1 A +/- 0.7 for 76-mers of PEO (M(w) approximately 3400), in excellent agreement with neutron scattering results for an equal sized PEG. Simulations of 9, 18, 27, 36, 44, 67, 76, 90, 112, 135, and 158-mers of the CG PEO (442 < M(w) < 6998) at low concentration in water show the experimentally observed transition from ideal chain to real chain behavior at 1600 < M(w) < 2000, in excellent agreement with the dependence of experimentally observed hydrodynamic radii of PEG. Hydrodynamic radii of PEO calculated from diffusion coefficients of the higher M(w) PEO also agree well with experiment. R(g) calculated from both all-atom and CG simulations of PEO76 at 21 and 148 mg/cm(3) are found to be nearly equal. This lack of concentration dependence implies that apparent R(g) from scattering experiments at high concentration should not be taken to be the chain dimension. Simulations of PEO grafted to a nonadsorbing surface yield a mushroom to brush transition that is well described by the Alexander-de Gennes formalism.

Proton diffusion in polyethylene oxide: Relevance to electrochromic device design

Polyethylene oxide is a frequently used component in polymer electrolytes developed for applications in electrochromic devices. The transmittance variation may occur as a result of either proton or lithium ion intercalation into the electrochromic films. Impedance spectroscopy data in the low-frequency space-charge relaxation regime can be used to obtain estimates of ion concentrations and ion diffusion coefficients in ion-conducting materials. We apply this method to literature data for pure polyethylene oxide where the residual conductivity is believed to be due to protons. The obtained diffusion coefficient is found to be in the order of, or higher than, reported lithium ion diffusion coefficients in low molecular weight polyethylene oxide. Hence it is likely that proton intercalation will be of importance for electrochromic devices, provided there is a significant amount of protons present.

Characterization of (PEO)LiClO4‐Li1.3Al0.3Ti1.7(PO4)3 composite polymer electrolytes with different molecular weights of PEO

AbstractA group of polyethylene oxide (PEO)LiClO4‐Li1.3Al0.3Ti1.7(PO4)3 composite polymer electrolyte (CPE) films was prepared by the solution‐cast method. In each film, EO/Li = 8 and the Li1.3Al0.3Ti1.7(PO4)3 content of 15 wt % were fixed, but the number averaged molecular weight of PEO (Mn) was altered from 5 to 7 × 104 to 106, 2.2–2.7 × 106, 3–4 × 106, 4–5 × 106, and 5.5–6 × 106, respectively. Several techniques including X‐ray diffraction (XRD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and electrical impedance spectroscopy (EIS) were used to characterize the CPE films. LiClO4 was found to have a strong tendency to complex with PEO, but Li1.3Al0.3Ti1.7(PO4)3 was rather dispersed in PEO matrix. DSC analysis revealed that the amorphous phase was dominant in the CPE films although the PEOs before‐use was considerably crystalline. SEM study showed smooth and homogeneous morphologies of the films with low molecular weight PEO and a dual phase characteristic for those with high molecular weight PEO. EIS results indicated that the CPE films are all ionic conductor and the conducting behavior obeys Vogel‐Tamman‐Fulcher (VTF) equation. The parameters in VTF equation were obtained and discussed by taking into considerations PEO molecular weights and crystallinities of the CPE films. Of all the films, the one with PEO with the smallest Mn = 5–7 × 104 had the maximum conductivity, i.e., 1.590 × 10−5 S cm−1 at room temperature and 1.886 × 10−3 S cm−1 at 373 K. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4269–4275, 2006

Study on the properties of crosslinking of poly(ethylene oxide) and hydroxyapatite–poly(ethylene oxide) composite

AbstractThis study covers the crosslinking of poly(ethylene oxide) (PEO) and its composite with calcium hydroxyapatite (HA), their mechanical and swelling properties, and morphology. Sheets of the composites of PEO (two different grades with Mv: 5 × 106 and 2 × 105) and HA and neat PEO were prepared by compression molding. The prepared composite and PEO (0.1‐mm‐thick) sheets were crosslinked with exposure of UV‐irradiation in the presence of a photoinitiator, acetophenone (AP). This simple method for crosslinking, induced by UV‐irradiation in the presence of AP, yielded PEO with gel content up to 90%. Gel content, equilibrium swelling ratio, and mechanical and morphological properties of the low molecular weight polyethylene oxide (LMPEO)–HA crosslinked and uncrosslinked composites were evaluated. Although the inclusion of HA into LMPEO inhibits the extent of crosslinking, the LMPEO–HA composite with 20% HA by weight shows the highest gel content, with appreciable equilibrium swelling and mechanical strength. The growth of HA in simulated body fluid solutions on fractured surfaces of LMPEO and also LMPEO–HA was found to be very favorable within short times. The dimensional stability of these samples was found to be satisfactory after swelling and deposition experiments. The good compatibility between the filler hydroxyapatite and poly(ethylene oxide) makes this composite a useful tissue‐adhesive material. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 488–496, 2003

Photoreactive self-assembling polyethers for biomedical coatings

A new family of diblock surfactants based on low molecular weight polyethylene oxide and a more hydrophobic block containing benzophenone is reported. These surfactants self-assemble out of aqueous solution onto hydrophobic surfaces and can be covalently bonded to the surface via irradiation with ultraviolet light. Such films on polystyrene possess a static contact angle with water of 55.7±1.7°. Non-specific adsorption of several proteins on these surfaces is compared, with the greatest reduction being 89% for fibrinogen. In addition, the coatings have been shown to reduce adherence of the bacterium Proteus mirabilis by 95.5%. Surfaces were investigated with atomic force microscopy and time of flight-secondary ion mass spectroscopy (TOF-SIMS), which revealed very thin uniform coatings. Such thin wettable and passivating coatings may be desirable on applications where small spatial separations must be preserved.

Fumed silica-based composite polymer electrolytes: synthesis, rheology, and electrochemistry

An overview of our research is presented on developing composite polymer electrolytes (CPEs) based on low-molecular weight polyethylene oxide (PEO) (namely, poly(ethylene glycol) dimethyl ether), lithium salts (e.g. lithium triflate, lithium imide, etc.), and fumed silica. These CPEs demonstrate high room-temperature conductivites (>10 −3 S/cm), mechanical strength, and form stable interfaces with lithium metal as a result of the fumed silica. The surface groups on the fumed silica determine the mechanical properties of the CPE while the low-molecular weight PEO and lithium salt determine the ionic transport properties. These CPEs show promise as electrolytes for the next generation of rechargeable lithium batteries.

In vitro blood compatibility of surface-modified polyurethanes

Polyurethanes have proven durable materials for the manufacture of flexible trileaflet heart valves, during in vitro tests. The response of two polyurethanes of differing primary structure to parameters of blood compatibility has now been investigated, using an in vitro test cell. Platelet ( β-thromboglobulin) release, complement (C3a) activation, the activation of free plasma and surface-bound factor XII were studied using fresh, human blood (no anticoagulant) or citrated plasma in control and surface-modified polyurethane. Surface modifications were designed to affect material thrombogenicity and included covalent attachment of heparin, taurine, a platelet membrane glycoprotein fragment, polyethylene oxide (PEO), 3-aminopropyltriethoxysilane, and glucose or glucosamine. Unmodified control polyurethanes caused platelet release and complement activation. High molecular weight (2000 D) polyethylene oxide reduced platelet release slightly but only glucose attachment to the surface produced a significant reduction in platelet activation. All modifications reduced C3 activation compared with controls, but the greatest reduction was achieved with polyethylene oxide attachment or glycosylation. Most surface modifications were more activating of factor XII, both in plasma and on the material surfaces, than the control polyurethanes. Heparin and high molecular weight PEO produced the greatest activation of factor XII in the free plasma form, but low molecular weight PEO and glucosamine produced the greatest activation of surface-bound factor XIIa. The least activating surfaces, affecting both free plasma and surface-bound factor XIIa, were those treated with platelet membrane glycoprotein fragment and glucose. PEO surfaces performed relatively well, compared with controls and most surface modifications. The best overall surface, however, was the glucose-modified surface which was least activating considering all parameters of blood compatibility.

Dolomite-dolomite separation by a selective flocculation technique

The viability of physico-chemical purification methods such as selective flocculation for the separation of two components having similar chemical compositions and the same crystal structure but different surface properties is demonstrated. A loss of selectivity was observed in a dolomite-dolomite mixture when polyethylene oxide (PEO) (five million molecular weight) was used as the flocculant. Heteroflocculation was minimized using a low molecular weight PEO (MW ≈ 105) as a site blocking agent (SBA). Near complete separation was achieved at pH 10.5 at the 100% recovery level.

Endothelial cell binding to Dacron modified with polyethylene oxide and peptide.

Polyethylene oxide (PEO) was incorporated into the surface of Dacron (PET) vascular prosthetic material (crimped Bionit I, BNl) followed by covalent attachment of an endothelial cell (EC) adhesion peptide; Gly-Arg-Glu-Asp-Val-Tyr (GREDVY). This procedure provides the possibility of a surface selective for EC adherence. Optimal PEO incorporation with minimal fiber damage was achieved from 78% (vol) trifluoroacetic acid (TFA) as characterized by scanning electron microscopy, nuclear magnetic resonance, bromphenol blue staining, and tensile testing. By weight, there was 4.4 times as much 18.5kD PEO as 1.5kD PEO incorporated into PET, but there were 2.8 times as many molecules of low molecular weight PEO. Attachment of 125I-GREDVY to substrates increased as follows: BNJ < BNI - 18.5 kD PEO < BNI - 1.5 kD PEO. Polyethylene oxide size affected EC binding with high molecular weight material decreasing binding and low molecular weight PEO increasing attachment. GREDVY modification of BNI or either of the two BNI-PEOs gave small but consistently increased EC binding compared with the same preparation without GREDVY. In contrast, human fibroblasts cultured from umbilical vein showed decreased binding when GREDVY was attached to BNI or PEO modified BNI. These results indicate that selective EC binding to PET vascular prostheses can be achieved.

Direct measurements of steric interactions between mica surfaces covered with electrostatically bound low-molecular-weight polyethylene oxide

The forces between two mica surfaces covered with electrostatically anchored chains of a low-molecularweight (mol wt ∼ 1900 g/mole) polyethylene oxide ester of lysine (PEO-lysine) have been measured directly in aqueous solutions. In dilute solutions of PEO-lysine the long-range forces observed can be accounted for by the DLVO theory. However, at separations below 10 nm a strong repulsive force of steric origin prevents the surfaces from reaching molecular contact. At higher PEO-lysine concentrations ( C > 10 −3 M) a long-range ( D < 50 nm) repulsive force not accounted for by DLVO theory is present. It is suggested that this force, which is stronger on approach than on separation, is caused by PEO-lysine molecules weakly associated with the coated mica surface (for instance as counter ions), but not electrostatically bonded to it. Upon addition of salt or upon increasing the temperature, the range of the repulsive force decreases and the hysteresis disappears. The repulsive force observed under such conditions originates from the interaction between electrostatically bonded polyethylene oxide chains. The water content in a compressed adsorbed PEO-lysine monolayer was found to be substantial. At 23°C the adsorbed layer contains about six water molecules per ethylene oxide unit and at 55°C there is about four.