Polyethylene Oxide Concentration Research Articles

Morphologies of electrospun fibers of lignin in poly(ethylene oxide)/N,N‐dimethylformamide

ABSTRACTThe effects of polyethylene oxide (PEO) molecular weight (Mv), and volume fraction ( ) on the morphology of electrospun sulfur free softwood lignin nanofibers were investigated. Small amounts of PEO were used during preparations of the solutions to aid the electrospinning process. It was found that tripling the PEO volume fraction resulted in a transition from semi‐dilute un‐entangled to semi‐dilute entangled solutions. Conversely, the solution remained in the semi‐dilute un‐entangled regime as the molecular weight was increased by five times. The effects of molecular weight and volume fraction of PEO both on entanglement density and fiber morphology were unified by scaling PEO viscosities as a function of . We investigated and discussed conditions that would produce smooth fibers and conditions that would produce fibers with beads. In the case of beads‐on‐a‐string formation, bead widths remained constant regardless of the molecular weight and concentration of PEO, but the bead length changed. Additionally, we observed a decrease in the diameter of the fibers and the dimension of beads (length and width of beads) with an increase in the electric field used for electrospinning. The aspect ratio of beads increased with increases to both the electric field and the PEO molecular weight or concentration. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 44172.

Investigation of particle lateral migration in sample-sheath flow of viscoelastic fluid and Newtonian fluid.

In this work, particle lateral migration in sample-sheath flow of viscoelastic fluid and Newtonian fluid was experimentally investigated. The 4.8-μm micro-particles were dispersed in a polyethylene oxide (PEO) viscoelastic solution, and then the solution was injected into a straight rectangular channel with a deionised (DI) water Newtonian sheath flow. Micro-particles suspended in PEO solution migrated laterally to a DI water stream, but migration in the opposite direction from a DI water stream to a PEO solution stream or from one DI water stream to another DI water stream could not be achieved. The lateral migration of particles depends on the viscoelastic properties of the sample fluids. Furthermore, the effects of channel length, flow rate, and PEO concentration were studied. By using viscoelastic sample flow and Newtonian sheath flow, a selective particle lateral migration can be achieved in a simple straight channel, without any external force fields. This particle lateral migration technique could be potentially used in solution exchange fields such as automated cell staining and washing in microfluidic platforms, and holds numerous biomedical applications.

AC and DC electrospinning of hydroxypropylmethylcellulose with polyethylene oxides as secondary polymer for improved drug dissolution

Alternating current electrospinning (ACES) capable to reach multiple times higher specific productivities than widely used direct current electrospinning (DCES) was investigated and compared with DCES to prepare drug-loaded formulations based on one of the most widespread polymeric matrix used for commercialized pharmaceutical solid dispersions, hydroxypropylmethylcellulose 2910 (HPMC). In order to improve the insufficient spinnability of HPMC (both with ACES and DCES) polyethylene oxide (PEO) as secondary polymer with intense ACES activity was introduced into the electrospinning solution. Different grades of this polymer used at as low concentrations in the fibers as 0.1% or less enabled the production of high quality HPMC-based fibrous mats without altering its physicochemical properties remarkably. Increasing concentrations of higher molecular weight PEOs led to the thickening of fibers from submicronic diameters to several microns of thickness. ACES fibers loaded with the poorly water-soluble model drug spironolactone were several times thinner than drug-loaded fibers prepared with DCES in spite of the higher feeding rates applied. The amorphous HPMC-based fibers with large surface area enhanced the dissolution of spironolactone significantly, the presence of small amounts of PEO did not affect the dissolution rate. The presented results confirm the diverse applicability of ACES, a novel technique to prepare fibrous drug delivery systems.

Preparation of porous PVDF nanofiber coated with Ag NPs for photocatalysis application

The porous Polyvinylidene fluoride (PVDF) nanofibers were prepared by leaching method using polyethylene oxide (PEO) as porogen for the first time. The influences of the molecular weight (MW) and concentration of PEO, and the leaching solution on the morphology and the surface area of the porous PVDF nanofiber were systematically investigated. Polyethylene glycol 6000 (PEG6000) showed a better pore-forming effect. Optimized preparation parameters were obtained. With the ratio of PEG6000/PVDF reaching 1:1, the surface area of the resulting porous PVDF nanofiber was about three times higher than that of the pure PVDF nanofiber. Moreover, NaClO solution as leaching solution showed a very limited influence on the surface area of porous PVDF nanofiber. Afterwards, Ag NPs coated PVDF (Ag/PVDF) nanofiber was prepared by physical adsorption of Ag ions and in-situ reduction reaction using sodium borohydride as reductant. The photoactivity of Ag/PVDF nanofiber was evaluated by the photodegradation of methyl orange (MO) under visible light irradiation. Ag/PVDF nanofiber showed a better photoactivity than PVDF-Ag nanofiber prepared by the ex-situ blending method.

Structural effect of glyme-Li(+) salt solvate ionic liquids on the conformation of poly(ethylene oxide).

The conformation of 36 kDa polyethylene oxide (PEO) dissolved in three glyme-Li(+) solvate ionic liquids (SILs) has been investigated by small angle neutron scattering (SANS) and rheology as a function of concentration and compared to a previously studied SIL. The solvent quality of a SIL for PEO can be tuned by changing the glyme length and anion type. Thermogravimetric analysis (TGA) reveals that PEO is dissolved in the SILs through Li(+)-PEO coordinate bonds. All SILs (lithium triglyme bis(trifluoromethanesulfonyl)imide ([Li(G3)]TFSI), lithium tetraglyme bis(pentafluoroethanesulfonyl)imide ([Li(G4)]BETI), lithium tetraglyme perchlorate ([Li(G4)]ClO4) and the recently published [Li(G4)]TFSI) are found to be moderately good solvents for PEO but solvent quality decreases in the order [Li(G4)]TFSI ∼ [Li(G4)]BETI > [Li(G4)]ClO4 > [Li(G3)]TFSI due to decreased availability of Li(+) for PEO coordination. For the same glyme length, the solvent qualities of SILs with TFSI(-) and BETI(-) anions ([Li(G4)]TFSI and [Li(G4)]BETI) are very similar because they weakly coordinate with Li(+), which facilitates Li(+)-PEO interactions. [Li(G4)]ClO4 presents a poorer solvent environment for PEO than [Li(G4)]BETI because ClO4(-) binds more strongly to Li(+) and thereby hinders interactions with PEO. [Li(G3)]TFSI is the poorest PEO solvent of these SILs because G3 binds more strongly to Li(+) than G4. Rheological and radius of gyration (Rg) data as a function of PEO concentration show that the PEO overlap concentrations, c* and c**, are similar in the three SILs.

EXTENDED RELEASE OF NEVIRAPINE USING ELEMENTARY OSMOTIC PUMP TABLETS

Nevirapine is currently administered twice daily in combination with lamivudine and stavudine for the treatment of HIV infection. Previo us study suggests that once daily regimen of nevirapine provides a higher peak and lower trough levels compared with twice daily re gimen of the same drug and has proved to be equally efficient. Presently extended release formulation of nevirapine is used for HIV infection in clinical practice; howev er it lacks zero - order characteristics. The present study aimed to design elementary os motic pump tablet of nevirapine as once daily preparation to achieve zero - order characteristics. The elementary osmotic pump tablets were developed using variable concentration of poly ethylene oxide (polymer) and potassium ch loride (osmogen) with variable orifice diameter and evaluated for physico - chemical and release characteristics. The elementary osmotic pump tablets released the drug at a zero - order rate over a period of 24 hours and the release rate of the drug was found to be influenced by the variab les employed. The amount of poly ethylene oxide had a significant effect on the release rate and a direct correlation was observed between the concentration of potassium chloride and the drug release rate. It was seen that the formulations showed no remark able changes in the physico - chemical and release characteristics as well as drug content after the stability studies. The results demonstrate that elementary osmotic pump tablet of nevirapine is beneficial as once daily preparation for effecti ve control of HIV infection.

Shaken but not stirred: The formation of reversible particle – polymer gels under shear

Abstract Some dispersions of clay and silica particles in water in the presence of relatively high molecular weight polyethyleneoxide (PEO), which are fluid when at rest, become solid-like after a quick shake to such an extent that they can be held in the hand. On leaving the dispersions for a certain period of time, minutes to days depending on the polymer molecular weight and concentration, the dispersions become liquid-like again. These dispersions have been called “shake gels”, and a number of physical variables are determinant for producing the gel and controlling its behavior. In this work, we have studied the effect of the shape and size of the particles and of the PEO molecular weights. To that aim, we have mapped the “phase” behavior of silica (Ludox TM-50), montmorillonite and laponite dispersions in presence of PEO of different molecular weight. Shake gels are formed under certain concentrations of particles and PEO. The necessary degree of particle coverage for shake gel formation seems to depend on the particle shape. Whereas in the case of disc-shaped particles this limit is around the saturation concentration, in the case of spherical particles the limit is around 2/3 of the particle surface saturation. On the other hand, we observe some differences between montmorillonite (micrometer-size particles) and laponite (nanometric particles) dispersions. When we shake the former we find in some cases an important and irreversible phase separation; on the contrary, in the case of the laponite dispersions, the phase separation is far less frequent and extensive. Finally, we have found that the nature of the applied shear field has a profound effect on the sample behavior. When we place the dispersions in a conventional rheometer and shear them at moderate shear rate, for many minutes the gel is not formed. However, shaking it by hand or extruding it through a syringe brings about this effect in a matter of seconds.

Controllable transition from finger-like pores to inter-connected pores of PLLA membranes

Poly (l-lactic acid) (PLLA) flat sheet membranes with inter-connected pores were prepared via non-solvent induced phase separation process. Polyethylene oxide (PEO) with molecule weight of 100kD was used as additives. The morphology evolution from the partial to total inter-connected pores in cross section was accomplished by adjusting the PEO concentration. Besides, the effect of different molecule weight of polyethylene glycol (PEG), high coagulation intensity, different mass fraction ratios of PEO to PLLA and the casting solution exposure time in air on morphologies of PLLA membranes were also investigated respectively. Finally, as a hemodialysis membrane, the water permeability, solute clearance rate and mechanical properties were determined. It was shown that PLLA membrane with highly inter-connected pores exhibited a higher water flux of 225L/hm2 and tensile strain of 83%. The clearance of the as-prepared membranes to urea and lysozyme is 77% and 33% respectively, while keeping BSA rejection with 90%.

폴리락틱산, 폴리카프로락톤, 폴리에틸렌 옥사이드 삼성분계 블렌드의 형태학적 변화와 이들이 의료용 스캐폴더의 기계적 특성에 미치는 영향

Ternary blends of poly(L-lactic acid) (PLLA), poly(<TEX>${\varepsilon}$</TEX>-caprolactone) (PCL) and polyethylene oxide (PEO) were produced with different concentrations of components via melt blending. By leaching the PEO from the samples by water, porous materials were obtained with potential application for bio scaffolds. Sample porosity was evaluated by calculating the ratio of porous scaffold density (<TEX>${\rho}^*$</TEX>) to the non-porous material density (<TEX>${\rho}_s$</TEX>). Highest porosity (51.42%) was related to the samples containing 50 wt%. of PEO. Scanning electron microscopy (SEM) studies showed the best porosity resulted by decreasing PLLA/PCL ratio at constant concentration of PEO. Crystallization behavior of the ternary blend samples was studied using differential scanning calorimetry (DSC). Results revealed that the crystallinity of PLLA was improved by addition of PEO and PCL to the samples. The porosity plays a key role in governing the compression properties. Mechanical properties are presented by Gibson-Ashby model.

Tribological properties of carbon nanotube–polyethylene oxide composite coatings

The effect of polyethylene oxide (PEO) inclusion in carbon nanotube (CNT) coating on the tribological properties of the composite coating was investigated. CNT/PEO composite coatings with 12 different weight fractions were fabricated by using the spin-coating method on pre-cleaned Si (1 0 0) substrates. Wear tests were performed using a reciprocating tribo-tester under an applied load of 10 mN and a speed of 4 mm/s. A 1.6 mm diameter stainless-steel ball was used as the pin and the corresponding Hertzian contact pressure was calculated to be ∼20 kPa. From the experimental results, it was shown that the steady-state friction coefficients for the CNT/PEO coatings gradually decreased from ∼0.47 to ∼0.3 as the concentration of PEO increased from 0 wt.% to 75 wt.%. The wear volume of the CNT/PEO composite coating rapidly increased with increasing amount of PEO when the weight fraction of PEO was comparatively low. The wear volume reached the maximum value for 87/13 wt.% of CNT/PEO coating and showed a continuous decrease in the wear volume with further increase in the PEO weight fraction. Morphological analyses of the wear pattern revealed that wear mechanism of the composite coating varied with respect to PEO concentration. The overall experimental results demonstrated that the tribological properties of CNT-based coatings could be significantly improved by adding an optimum amount of PEO. The reason for such an improvement was attributed to the enhancement of interfacial forces within the composite coating due to the presence of PEO.

An unexpected particle oscillation for electrophoresis in viscoelastic fluids through a microchannel constriction

Electrophoresis plays an important role in many applications, which, however, has so far been extensively studied in Newtonian fluids only. This work presents the first experimental investigation of particle electrophoresis in viscoelastic polyethylene oxide (PEO) solutions through a microchannel constriction under pure DC electric fields. An oscillatory particle motion is observed in the constriction region, which is distinctly different from the particle behavior in a polymer-free Newtonian fluid. This stream-wise particle oscillation continues until a sufficient number of particles form a chain to pass through the constriction completely. It is speculated that such an unexpected particle oscillating phenomenon is a consequence of the competition between electrokinetic force and viscoelastic force induced in the constriction. The electric field magnitude, particle size, and PEO concentration are all found to positively affect this viscoelasticity-related particle oscillation due to their respective influences on the two forces.

Characterization and some properties of cellulose acetate-co-polyethylene oxide blends prepared by the use of gamma irradiation

Cellulose acetate (CA), polyethylene oxide (PEO) copolymer blend was prepared using γ-rays as initiator. PEO as an additive was added with different concentrations (0 – 5%) based on cellulose acetate. As the PEO is water soluble, some portions of them were extracted into aqueous solution. To overcome this, the PEO additives were crosslinked with N,N′Methylene bis-acrylamide (MBAAm) to be stably entrapped in the CA matrix. The efficiency was calculated to be 100%. Morphological changes using scanning electron microscope (SEM) and the bulk properties such as water sorption, electrical conductivity, and chemical stability were investigated. The thermal stability of the developed copolymer blend has also been studied using thermogravimetric analysis (TGA), and differential scanning calorimeter (DSC). Different variations of the copolymerization were studied such as crosslinker concentration and ratio of PEO to cellulose acetate. It was observed that the addition of small amounts of PEO 3 weight % as an additive resulted in a considerable change of the thermal characteristics.

Preparation and Characterization of PLA-PEO Bicomponent Fibers with Porous-Smooth Surface by Co-Electrospinning

Poly (lactic acid) (PLA)/polyethylene oxide (PEO) bicomponent fibers with porous and smooth surface on different side of the same fibers were fabricated by co-electrospinning technique. Specific solvent systems were used deliberately to induce pore formation on PLA phase. The results showed that the porous-smooth surface fibers were obtained using PLA-PEO flow rate ratio of 0.75:0.25 to 0.25:0.75 ml/hr. While, Fiber size decreased with decrease in PEO concentration and PEO flow rate ratio, the applied voltage had small effect on fiber size change. After PEO phase removal via selective dissolution with water, the C-shape PLA fibers with porous surface was generated.

The Effect of Processing Parameters Onpoly (Lactic Acid)/Poly(Ethylene Oxide)Bicomponentultrafine Fibersby Co-Electrospinning

Poly (lactic acid) (PLA)/polyethylene oxide (PEO) bicomponent fibers werefabricated by co-electrospinning technique in a side by side configuration. Effect of PEO concentration, PLA and PEO solution flow rate and an applied voltage on formation, size and morphology of the fibers were investigated. The results showed that the fibers size increased with increasing PEO concentration, PEO flow rate ratio and applied voltage. The composition of the fibers was confirmed by IR spectrum. Additionally, by pairing PEO, which is a water soluble polymer, with PLA, follow by PEO phase removal in water, a C-shaped ultrafine fiber was prepared.

Tailoring of Morphology and Surface Properties of Syndiotactic Polystyrene Aerogels

This study evaluates a method for rendering syndiotactic polystyrene (sPS) aerogels hydrophilic using polyethylene oxide (PEO) of different molecular weights. The highly porous sPS aerogels are inherently hydrophobic although applications involving absorption of moisture and removal of particulate solids may benefit from the high surface area of sPS aerogels provided some degree of hydrophilicity is induced in these materials. In this work, sPS gels are prepared by thermo-reversible gelation in tetrahydrofuran in the presence of PEO. The gels are dried under supercritical conditions to obtain aerogels. The aerogels are characterized by scanning electron microscopy, nitrogen-adsorption porosimetry, helium pycnometry, and contact angle measurements. The data reveal that the pore structures and surface energy can be controlled by varying the concentration and molecular weight of PEO and using different cooling rates during thermo-reversible gelation. In the first case, sPS aerogels, aerogels containing PEO of a low molecular weight or low concentration show superhydrophobic surface presenting the "lotus effect". In the second case, PEO at a higher concentration or with higher molecular weight forms phase-separated domains yielding new hydrophilic macropores (>10 μm) in the aerogel structures. These macropores contribute to the superhydrophobic surface with the "petal effect". The cooling rate during gelation shows a strong influence on these two cases.

Analysis of difference of proteins of gastric cancer tissue and adjacent normal tissue by capillary electrophoresis with laser-induced fluorescence detection

Gastric cancer is one of the familiar malignant tumors in clinical study. Research on tumor biomarkers has increased noticeably in recent years. An experimental method of protein separation by capillary electrophoresis with laser-induced fluorescence detection (CE-LIF) was established and improved. A series of effects on capillary electrophoresis (CE) were studied, such as the dynamic coating method of capillary, concentration of polyethylene oxide (PEO) as sieving medium, pH of running buffer, separation voltage, temperature and fluorescent dye. Then the optimized method was established for the determination of gastric cancer tissue and adjacent normal tissue. According to the analysis of the protein fingerprints, the results showed that the similarity of protein was up to 0.8. The molecular masses of differential proteins were almost between 50,000 Da and 100,000 Da. It indicated that these proteins might be potential biomarkers for cancer diagnosis which may reduce the searching scope. By statistical analysis of histological classification and electrophoresis peak numbers, this method was demonstrated reliably, and had the potential for clinical applications.

Rapid separations of nile blue stained microorganisms as cationic charged species by chip‐CE with LIF

Rapid detection of microorganisms by alternative methods is desirable. Electromigration separation methods have the capability to separate microorganisms according to their charge and size and laser-induced fluorescence (LIF) detection have single-cell detection capability. In this work, a new combined separation and detection scheme was introduced using chip-based capillary electrophoresis (chip-CE) platform with LIF detection. Three microorganisms Escherichia coli, Staphylococcus aureus, and Candida albicans were selected as representatives of Gram-positive bacteria, Gram-negative bacteria, and fungi. While their cells carry an overall negative charge in neutral to alkaline pH, staining them with nile blue (NB) provided highly sensitive LIF detection with excitation and emission wavelengths at 635 nm and 685 nm, respectively, and at the same time, the overall charge was converted to positive. Electrolyte pH and concentration of polyethylene oxide (PEO) significantly affected the resolution of the microorganisms. Their optimal separation in the 14 mm separation channel was achieved in less than 30 s (R(s) > 5.3) in an electrolyte consisting of 3.94 mM Tris, 0.56 mM boric acid, 0.013 mM ethylenediaminetetraacetic acid disodium salt dihydrate (pH 10.5), and 0.025% PEO, with injection/separation voltages of +1000/+1000 V. The separation mechanism is likely employing contributions to the overall cationic charge from both the prevalently anionic membrane proteins and the cationic NB. Importantly, the resulting cationic NB-stained cells exhibited excellent separation selectivity and efficiency of ∼38000 theoretical plates for rapid separations within 30-40 s. The results indicate the potential of chip-CE for microbial analysis, which offers separations of a wide range of species with high efficiency, sensitivity, and throughput.

Optimizing the Poly Ethylene Oxide Flocculation Process for Isolating Lignin of Prehydrolysis Liquor of a Kraft-Based Dissolving Pulp Production Process

In this work, poly ethylene oxide (PEO) with various molecular weights (MW)s was employed to separate the lignin of prehydrolysis liquor (PHL) of a kraft-based dissolving pulp process. The results revealed that, the higher the MW and concentration of PEO in the PHL at pH 2, the higher are the removals of lignin and chemical oxygen demand (COD) but with a marginal removal of sugars. Alternatively, poly aluminum chloride (PAC) (200 mg/L) and PEO (8 MDa MW) (200 mg/L) were employed in a dual polymer system to extract the lignin, and the PAC/PEO system (MWs of 2 kDa/8 MDa) was more effective than the PEO/PEO system (MWs of 0.1 MDa/8 MDa) in removing lignin and COD of PHL. The maximum lignin, sugar, and COD removals were 46%, 18.8%, and 32%, respectively, under the conditions of 400 mg/g PEO (with a MW of 8 MDa) at pH 2 and room temperature in a singular PEO system.

Multi-Phase Composite Nanofibers via Electrospinning of Latex Containing Nanocapsules with Core-Shell Morphology

Nanocapsules containing hexadecane (HD) as core material and polystyrene (PS) as shell, were electrospun with polyethylene oxide (PEO) as a matrix material into the fiber webs. The morphology and thermal properties of PEO fibers containing (1) both PS nanocapsules with core-shell morphology and solid PS particles, (2) only solid PS particles, and (3) without any PS particles, were compared and the effect of PEO concentration on morphology of the resultant fibers have been studied. The resultant fibers were characterized by means of Transmission Electron Microscopy (TEM), Differential Scanning Calorimetry (DSC), and Thermogravimetric Analysis (TGA). Both TEM observation and DSC analyses confirmed that the PS nanocapsules were encapsulated within the PEO nanofibers. The fibers had an average diameter of 950 nm for nanocapsules containing parts, 300 nm for solid particles containing parts, and 150 nm for usual parts. The phase change temperatures and phase transition heat of the produced fibers were determined by DSC analyses. TGA was also used to confirm the preparation of multi phase fibers and to determine the amount of HD within the fibers.

Artificial neural networks modeling of electrospinning of polyethylene oxide from aqueous acid acetic solution

AbstractThe artificial neural networks (ANNs) were used to provide a model for investigating the relationships of the electrospinning parameters with the diameter of polyethylene oxide (PEO) nanofibers from acid acetic aqueous solution. The effects of four parameters including PEO concentration, acetic acid concentration, applied voltage, and temperature of the electrospinning media on the nanofibers mean diameter were investigated. To train, test, and valid the model, three datasets of the input variables with random values were prepared and the mean diameters obtained were taken as the output for the network. The datasets were analyzed by ANNs software and the correlation coefficient, R‐squared (R2), between the predicted values of the nanofibers mean diameter and actual amount were obtained. The results demonstrate the capability of the ANNs model for predicting the nanofibers diameter. The 3‐D plots generated from the model show complex and nonlinear relationships between the parameters and nanofibers diameter. From the model, increasing the PEO concentration above a critical point leads to a sharp increase in the nanofibers mean diameter. The effects of applied voltage and temperature are mainly dependent on the PEO concentration. The acetic acid concentration, in general shows a direct relation with the nanofibers mean diameter. The plots also show that to produce nanofibers with the lowest diameter, both the PEO concentration and AcOH concentration should be at lowest values regardless the applied voltage and temperature. In contrast, highest nanofibers diameters are obtained when the PEO concentration and AcOH concentration are at their high values. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012