Molecular Weight Poly Ethylene Oxide Research Articles

On the rheological properties of Silica – Poly(ethylene-oxide) dispersions: "Shake-gels" II The effect of silica concentration and molecular weight of polymer

Using rheological techniques, the effect of silica concentration and polyethylene oxide molecular weight has been investigated to follow the gelation/shear thickening behaviour of PEO silica water mixtures, a phenomenon which has become known as "shake gels”. By monitoring the viscosity as a function of the shear rate it was observed that at a critical shear rate the viscosity increased by many orders of magnitude. The higher the silica concentration and the higher the polymer molecular weight the lower the shear rate required for the gel to form. Once formed by dropping the shear rate to a low value or by monitoring the viscoelastic moduli the relaxation of the gel back into the liquid state could be followed. It was noted that the lower the polymer molecular weight or the lower the silica concentration the faster the relaxation process was. It is postulated that the silica particles effectively cross link the gel so that the more silica particles per polymer molecule would result in slower relaxation. Conversely in the gel formation stage the more silica particles per polymer the faster the gel forms are a consequence of the ease by which the silica particles can cross link to form the gel.

Covalently attached phosphonic acid‐Si2O3‐PEO polymer membranes for PEMFC applications

AbstractIn the context of growing interest in phosphonic acid proton exchange membranes (PEMs) for fuel cell applications, we report on new PEMs containing low‐cost polyethylene oxide (PEO) covalently linked by siloxane bonds, SiOSi, to phosphonic acid (PA). Key chemistry in the formation of these membranes involves hydrolysis and condensation reactions of triethoxysilyl propyl capped PEO and pre‐hydrolyzed dimethyl phosphonatoethyltrimethoxysilane (DMPTMS) giving PEO‐Si2O3‐PA and cross‐linked chain PEO‐Si2O3‐PEO organosilsesquioxane components. The Si2O3 can enhance membrane thermal and mechanical properties. The membrane formulations were varied by (a) reagent ratios (b) PEO molecular weights or using polypropylene oxide (PPO) (c) incorporating chain extending groups methylene diphenyl diisocyanate (MDI) or hexamethylene diisocyanate (HDI). These variations provided five membrane families, one of which afforded a complete group of robust membranes with weight% x of PA, PAx in range PA0–PA33. These were studied using ATR‐FTIR, dry membrane water uptake capacity, ion exchange capacity (IEC), and conductivity from room temperature to 120°C at 100% relative humidity. Conductivity increased with PAx reaching 15 mS cm−1 at 120°C, activation energy 0.1 eV, for membrane PA33 for which thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and energy dispersive X‐ray analysis (EDAX) are reported. A comparative performance of the five membrane families is presented.

Physical-Entanglements-Supported Polymeric Form Stable Phase Change Materials with Ultrahigh Melting Enthalpy.

With the rapid development of new energy and the upgrading of electronic devices, structurally stable phase change materials (PCMs) have attracted widespread attentions from both academia and industries. Traditional cross-linking, composites, or microencapsulation methods for preparation of form stable PCMs usually sacrifice part of the phase change enthalpy and recyclability. Based on the basic polymer viscoelasticity and crystallization theories, here, a kind of novel recyclable polymeric PCM is developed by simple solution mixing ultrahigh molecular weight of polyethylene oxide (UHMWPEO) with its chemical identical oligomer polyethylene glycol (PEG). Rheological and leakage-proof experiments confirm that, even containing 90% of phase change fraction PEG oligomers, long-term of structure stability of PCMs can be achieved when the molecular weight of UHMWPEO is higher than 7000kg mol-1 due to their ultralong terminal relaxation time and large number of entanglements per chain. Furthermore, because of the reduced overall entanglement concentration, phase change enthalpy of PCMs can be greatly promoted, even reaching to ≈185 J g-1, which is larger than any PEG-based form stable PCMs in literatures. This work provides a new strategy and mechanism for designing physical-entanglements-supported form stable PCMs with ultrahigh phase change enthalpies.

In vitro test methods for evaluating high molecular weight polyethylene oxide polymer induced hemolytic and thrombotic potential

To combat opioid abuse, the U.S. Food and Drug Administration (FDA) released a comprehensive action plan to address opioid addiction, abuse, and overdose that included increasing the prevalence of abuse-deterrent formulations (ADFs) in opioid tablets. Polyethylene oxide (PEO) has been widely used as an excipient to deter abuse via nasal insufflation. However, changes in abuse patterns have led to unexpected shifts in abuse from the nasal route to intravenous injection. Case reports identify adverse effects similar to thrombotic thrombocytopenic purpura (TTP) syndrome following the intravenous (IV) abuse of opioids containing PEO excipient. Increased risk of IV opioid ADF abuse compared to clinical benefit of the drug led to the removal of one opioid product from the market in 2017. Because many generic drugs containing PEO are still in development, there is interest in assessing safety consistent with generic drug regulation and unintended uses. Currently, there are no guidelines or in vitro assessment tools to characterize the safety of PEO excipients taken via intravenous injection. To create a more robust excipient safety evaluation tool and to study the mechanistic basis of HMW PEO-induced TMA, a dynamic in vitro test system involving blood flow through a needle model has been developed.

Oral fast-dissolving risperidone loaded electrospun nanofiber drug delivery systems for antipsychotic therapy

Risperidone is an antipsychotic drug classified as BCS Class II with low solubility at physiological pH and orally used in the treatment of schizophrenia. Electrospinning is one of the newest fabrication methods used for the development of fast soluble drug delivery systems. In this study, an orally disintegrating film (ODF) formulation of risperidone was developed with green electrospinning technique. Different molecular weight polyethylene oxide (PEO) as a polymer and xylitol or Kollidon VA64 as a disintegration agent were used for the preparation of formulations. Differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FT-IR) analyses were conducted as part of pre-formulation studies to identify possible incompatibilities in formulation components. We characterized ODFs based on their mechanical properties, shape and diameter of nanofibers, disintegration behavior, and in vitro dissolution profiles. A few wrinkles appeared on the surface of fibers prepared with xylitol, but a smooth surface was evident on Kollidon VA64 fibers. Disintegration studies performed in the simulated oral environment showed that ODFs disintegrate in as little as 1 s. The dissolution behavior of developed ODFs and commercial products was compared with a dissolution study in distilled water. The chosen formulations had acceptable mechanical properties with much faster dissolution compared to the commercially available product. In this study, risperidone ODF formulation was successfully produced and characterized. The study showed that risperidone-loaded nanofibers could provide a promising alternative to conventional oral dosage forms like tablets and capsules.

Measurement and control of extensional viscosity in barrier coating dispersions

This study aimed to understand the effect of various rheological additives on the extensional viscosity of barrier coating dispersions, as well as to understand the role extensional viscosity plays in stabilizing a liquid curtain. The apparent extensional viscosity was measured using two devices that create accelerating flows: a capillary viscometer and an orifice rheometer. Additives tested include several polyvinyl alcohols, a high molecular weight polyethylene oxide, and carboxymethylcellulose. Extensional viscosity plays a significant role in stabilizing a liquid curtain, as it slows down hole expansion and prevents impurities and disturbances from causing holes in the first place. Some of the additives could substantially increase the extensional viscosity of the dispersions without increasing the shear viscosity outside the typical range of processability for a curtain coater. Some of the additives exhibited coil-stretch transition, meaning they start increasing extensional viscosity above a certain extension rate. Polymers with low chain lengths exhibited finite extensibility, which indicates the polymer chain has fully extended and cannot provide further extensional viscosity, even though the extending force is increased. Polymeric additives with stiff or branched chains significantly raised shear viscosity without increasing extensional viscosity. Both methods could reliably measure extensional viscosity in curtain coating barrier dispersions.

Crystallization in blend of polycaprolactone and high molecular weight polyethylene oxide

The concentration distribution in blend of polyethylene oxide (PEO)/polycaprolactone (PCL) and subsequent crystallization were investigated with differential scanning calorimetry, in-situ small angle X-ray scattering and wide angle X-ray scattering. By using PEOs with a molecular weight of 1 × 106 g/mol (PEO1M) and 1 × 105 g/mol (PEO100k), respectively, it is revealed that in initial blend the concentration of PEO1M in PEO-rich region is higher than that determined by miscibility. This non-equilibrium distribution induced by crystallization is maintained after melting, since slow relaxation of PEO1M hinders the redistribution process. Crystallization behavior of blend with 25 % of PEO1M at different melting temperatures was further investigated. The crystallinity shows no dependence on melting temperature, while the long period of PEO1M decreases continuously when melting temperature exceeds 140 °C. This decrease indicates more PCL chains diffuse into PEO-rich regions with increasing temperature and molten PCL chains reduce the entanglement number of PEO1M as solvent. Moreover, the periodicity of PEO1M lamellae becomes worse when crystallization proceeds faster, which is related to slower exclusion of PCL chains.

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.

Single-step generation of double emulsions in aqueous two-phase systems

This communication presents a simple yet straightforward method for preparing water-in-water-in-water particle-stabilized double emulsions, also known as Pickering double emulsions. The approach involves using oppositely charged nanoparticles (OCNPs) in two distinct fluid phases, promoting self-assembly and the formation of aggregates with varying sizes and compositions. By enhancing the interfacial area through the adsorption of aggregates at the interface, this method increases the Gibbs detachment energy of particles between the two aqueous phases, forming stable double emulsions. Furthermore, we investigated the impact of the molecular weight of polyethylene oxide and dextran in the respective fluid phases and the mass ratio (M) of the OCNPs on double emulsion formation. The results demonstrate that the molecular weight of the polymers used in the aqueous phase is a critical parameter influencing the structural formation of the emulsion and the generation of double emulsions. Consequently, double emulsions are formed when equal molecular weight polymer mixtures are employed at an appropriate M, with the dispersed phase placed in the highly viscous continuous phase. The proposed method offers a one-step synthesis process, enabling easy preparation, and exhibits excellent stability for at least 30 days. This study represents the first reported approach for the one-step synthesis of multiple emulsions in an aqueous two-phase system utilizing a Pickering emulsion template.

Continuous Monitoring of the Hydration Behavior of Hydrophilic Matrix Tablets Using Time-Domain NMR.

Time-domain NMR (TD-NMR) was used for continuous monitoring of the hydration behavior of hydrophilic matrix tablets. The model matrix tablets comprised high molecular weight polyethylene oxide (PEO), hydroxypropyl methylcellulose (HPMC), and polyethylene glycol (PEG). The model tablets were immersed in water. Their T2 relaxation curves were acquired by TD-NMR with solid-echo sequence. A curve-fitting analysis was conducted on the acquired T2 relaxation curves to identify the NMR signals corresponding to the nongelated core remaining in the samples. The amount of nongelated core was estimated from the NMR signal intensity. The estimated values were consistent with the experiment measurement values. Next, the model tablets immersed in water were monitored continuously using TD-NMR. The difference in hydration behaviors of the HPMC and PEO matrix tablets was then characterized fully. The nongelated core of the HPMC matrix tablets disappeared more slowly than that of the PEO matrix tablets. The behavior of HPMC was significantly affected by the PEG content in the tablets. It is suggested that the TD-NMR method has potential to be utilized to evaluate the gel layer properties, upon replacement of the immersion medium: purified (nondeuterated) water is replaced with heavy (deuterated) water. Finally, drug-containing matrix tablets were tested. Diltiazem hydrochloride (a highly water-soluble drug) was employed for this experiment. Reasonable in vitro drug dissolution profiles, which were in accordance with the results from TD-NMR experiments, were observed. We concluded that TD-NMR is a powerful tool to evaluate the hydration properties of hydrophilic matrix tablets.

Effect of green synthesis bimetallic Ag@SiO2 core–shell nanoparticles on absorption behavior and electrical properties of PVA-PEO nanocomposites for optoelectronic applications

A green and easy technique was used to synthesize silver and silica (Ag@SiO2) core–shell nanoparticles (NPs) in the matrix blend polymers matrix. Core–shell nanoparticles were loaded into polyvinyl alcohol (PVA) and ultrahigh molecular weight polyethylene oxide (UHMW-PEO) blended polymer to fabricate new nanocomposite films (NCFs) using the developed solution-sonication-casting technique. The spectroscopic properties of the resultant films were investigated using x-ray diffraction (XRD), Fourier transforms infrared (FTIR), visible light microscope (OLM), field emission scanning electron microscope (FESEM), FESEM-energy dispersive spectroscope (FESM-EDX), UV/visible spectrometer, and LCR meter to investigate the structural, morphological, optical, and electrical characteristics. XRD revealed the presence of the semi-crystalline nature of PVA-UHMWPEO/ Ag@SiO2 NCFs. The degree of crystallinity increased after embedding. The NPs were well distributed within the NCFs according to OLM and SEM, and FESM-EDX confirmed the presence of C, O, Si, and Ag elements. FTIR spectrum observed strong bonding after the loading of NPs, and other peaks were hidden. The UV/visible spectrums suggested an absorption at ~ 210 nm. Based on the Tauc plot model, the optical bandgap (Eg) values decreased from 5.52 eV to 4.57 eV. The electrical conductivity values were significantly increased with the increasing frequency and (Ag@SiO2) core–shell nanoparticles (NPs) loading ratio. The PVA-UHMWPEO/Ag@SiO2 NCFs explained enhanced lattice strain. The obtained NCFs are suitable for use in various optoelectronic and nanodevice applications.

Determining critical overlap concentration of polyethylene oxide to support excipient safety assessment of opioid products

Intravenous administration of abuse-deterrent opioid products poses high safety risks, in part due to the presence of high molecular weight polymeric excipients. Previous in vivo studies in animal models have shown that the higher molecular weight (Mw) polymeric excipients like polyethylene oxide (PEO) were directly linked to such adverse responses as intravenous hemolysis and kidney damage. PEO polymers have been widely used in abuse-deterrent formulations (ADF) of opioid products, adding to concerns over the general safety of the opioid category due to the unknown safety risk from abuse via unintended routes. The current study focused on the determination of the critical overlap concentration (c*) at various PEO molecular weights to aid in explaining differences in observed adverse responses from previous animal studies on the intravenous administration of PEO solutions. Adverse in vivo responses may be related to the viscoelastic regime of the polymer solution, which depends not only on Mw but also on concentration. Having a localized polymer concentration in the blood above the c*, i.e., the transition from the dilute to semi-dilute entangled viscoelastic regime, may influence the flow behavior and interactions of cells in the blood. The relationship of c* to this combination of physical, chemical, and rheological effects is a possible driving force behind adverse in vivo responses.

Crystallization and phase separation in PEDOT:PSS/PEO blend thin films: Influence on mechanical and electrical properties at the nanoscale

Thin films of polymeric blends composed of poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) and polyethylene oxide (PEO) were investigated by varying the concentration of the two components over the entire range of compositions and the molecular weight of PEO. Phase separation and crystallization have been studied at different length scales by combining Atomic Force Microscopy (AFM) and Grazing Incidence Wide Angle X-ray Scattering (GIWAXS) using synchrotron light. Several different arrangements in the thin films of the two polymers constituting the blend were observed and discussed in detail, providing information about their reciprocal influence at the micro- and nano-scale. In addition to that, we were able to estimate quantitative nanomechanical and nanoelectrical properties via AFM and finally revealing the dependence of the thin films' physical properties on their composition and structure. By varying the blend composition, we achieved different coating capability, mechanical properties, and electrical conductivity. Furthermore, depending on the PEO molecular weight, the electrical response of the resulting blends’ thin films shows some differences. In the low range concentration, the blend thin films with high molecular weight PEO present coarser conducting paths than in those with the low molecular weight counterparts. For intermediate concentrations, a more effective phase segregation of PEDOT:PSS and PEO is achieved for high molecular weight PEO. These differences are also translated to different electrical conductivity.

Cytotoxicity evaluation of poly(ethylene) oxide nanofibre in MCF-7 breast cancer cell line

Biocompatible polymers have received significant interest from researchers for their potential in diagnostic applications. This type of polymer can perform with an appropriate host response or carrier for a specific purpose. The current study aims to fabricate and characterise poly(ethylene) oxide (PEO) nanofibres with different concentrations for cytotoxicity evaluation in human breast cancer cell lines (MCF-7) and to get an optimal PEO nanofibre concentration (permissible limit) as a suitable polymer matrix or carrier with potential use in diagnostic applications. The fabrication of PEO nanofibres was done using electrospinning and was characterised by structure and morphology, surface roughness, chemical bonding and release profiles. The functional effects of PEO nanofibres were evaluated with MTS assay and colony formation assay in MCF-7 cells. The results showed that viscosity plays a vital role in synthesising a polymer solution in electrospinning for producing beadless nanofibrous mats ranging from 4.7 Pa·s to 77.7 Pa·s. As the PEO concentration increases, the nanofibre diameter and thickness will increase, but the surface roughness will be decreased. The average fibre diameter for 5 wt% PEO, 6 wt% PEO and 7 wt% PEO nanofibres were 129 ± 70 nm, 185 ± 55 nm and 192 ± 53 nm, respectively. In addition, the fibre thickness for 4 wt% PEO, 5 wt% PEO, 6 wt% PEO and 7 wt% PEO nanofibres were 269 ± 3 μm, 664 ± 4 μm, 758 ± 7 μm and 1329 ± 44 μm, respectively. Contrarily, the surface roughness for 4 wt% PEO, 5 wt% PEO, 6 wt% PEO and 7 wt% PEO nanofibres were 55.6 ± 9 nm, 42.8 ± 6 nm, 42.7 ± 7 nm and 36.6 ± 1 nm, respectively. PEO nanofibres showed the same burst release pattern and rate due to the same molecular weight of PEO with a stable release rate profile after 15 min. It also demonstrates that the percentage of PEO nanofibre release increased with the increasing PEO concentration due to the fibre diameter and thickness. The findings showed that all PEO nanofibres formulations were non-toxic to MCF-7 cells. It is suggested that 5 wt% PEO nanofibre exhibited non-cytotoxic characteristics by maintaining the cell viability from dose 0–1000 μg/ml and did not induce the number of colonies. Therefore, 5 wt% PEO nanofibre is the optimal nanofibre concentration and was suggested as a suitable base polymer matrix or carrier with potential use for diagnostic purposes. The findings in this study have demonstrated the influence of cell growth and viability, including the effects of PEO nanofibre formulations on cancer progress characteristics to achieve a permissible PEO nanofibre concentration limit that can be a benchmark in medical applications, particularly diagnostic applications.

Nanoporous MgAl<sub>2</sub>O<sub>4</sub> coating on porous Al<sub>2</sub>O<sub>3</sub> support by aerosol deposition method for organic polymer filtration membrane

Ultra- and nanofiltrations are utilized for the separation of polymers and proteins. In this study, we have investigated the application of the MgAl2O4 membrane produced by the aerosol deposition (AD) method for the separation of a polymer. A MgAl2O4 ultrafiltration membrane on the porous Al2O3 support layer was produced with intentionally leaving nano-sized pores instead of a completely dense membrane. The filtration performance was investigated by removing 1 million molecular-weight polyethylene oxide (PEO) from water, and the rejection rate with the AD MgAl2O4 on Al2O3 support to PEO was ∼44 % at the differential pressure of only ∼0.1 MPa, which was three times higher than our previous report by the dip-coating MgAl2O4 on Al2O3 of ∼14 %.

Evaporation-controlled dripping-onto-substrate (DoS) extensional rheology of viscoelastic polymer solutions

Extensional flow properties of polymer solutions in volatile solvents govern many industrially-relevant coating processes, but existing instrumentation lacks the environment necessary to control evaporation. To mitigate evaporation during dripping-onto-substrate (DoS) extensional rheology measurements, we developed a chamber to enclose the sample in an environment saturated with solvent vapor. We validated the evaporation-controlled DoS device by measuring a model high molecular weight polyethylene oxide (PEO) in various organic solvents both inside and outside of the chamber. Evaporation substantially increased the extensional relaxation time lambda _{E} for PEO in volatile solvents like dichloromethane and chloroform. PEO/chloroform solutions displayed an over 20-fold increase in lambda _{E} due to the formation of an evaporation-induced surface film; evaporation studies confirmed surface features and skin formation reminiscent of buckling instabilities commonly observed in drying polymer solutions. Finally, the relaxation times of semi-dilute PEO/chloroform solutions were measured with environmental control, where lambda _{E} scaled with concentration by the exponent m=0.62. These measurements validate the evaporation-controlled DoS environment, and confirm that chloroform is a good solvent for PEO, with a Flory exponent of nu =0.54. Our results are the first to control evaporation during DoS extensional rheology, and provide guidelines establishing when environmental control is necessary to obtain accurate rheological parameters.

Tuning the bandgap and absorption behaviour of the newly-fabricated Ultrahigh Molecular weight Polyethylene Oxide- Polyvinyl Alcohol/ Graphene Oxide hybrid nanocomposites

Graphene nanosheets are promising nanofillers to the tunable structure, properties of materials, and optical bandgap. This search focuses on investigating the new nanocomposites of Ultra-high molecular weight polyethylene oxide (UHMWPEO) with different loading ratios of polyvinyl alcohol (PVA) reinforced with graphene oxide (GO) by applying the modified solution-sonication-casting method. Fourier-transform infrared spectroscopy (FTIR) shows strong interfacial interaction between the blended polymers and GO nanosheets in the nanocomposites. X-Ray diffraction (XRD) reveals a significant shifting in the PEO and reduction in the crystallinity. Optical microscopy (OM) images exhibit fine homogeneity of the polymer in the matrix with excellent dispersal of GO in nanocomposites as supported by scanning electron microscopy (SEM). Attractively, the samples with a higher ratio of UHMWPEO exhibit better optical behavior, and great improvements were presented after the contribution of GO. UV-visible spectroscopy has characterized the absorption, absorption coefficient, real and imaginary, bandgap, and other parameters. The allowed bandgap was significantly enhanced by reducing up to 80%, whereas the forbidden bandgap was improved by up to 160% of the nanocomposites. Additionally, nanocomposites exhibited significant adsorption of radiation-ray, especially after the contribution of GO. The findings are promising as various applications could come to the fore: radiation protection, spectroscopy devices, and other applications.

Experimental Investigation of Polyethylene Oxide Polymer Solutions for Enhanced Oil Recovery in Low-Permeability Carbonate Rocks

SummaryNew experiments using polyethylene oxide (PEO) polymer were performed to evaluate its potential for enhanced oil recovery (EOR) applications in low-permeability reservoirs. This is the first time that high molecular weight PEO solutions have been shown to have favorable transport in low-permeability (~20 md) carbonate cores and the first time PEO has been shown to improve oil recovery in a fractured carbonate core. Rheology measurements in synthetic seawater show the higher viscosity of PEO solutions compares favorably to the viscosity of acrylamide–sodium acrylate (AM-AA) copolymers of similar molecular weight because PEO is less sensitive to hardness and high salinity. Filtration experiments using 0.45 μm cellulose filters show very favorable filtration ratios of PEO with a molecular weight of 4 million g/mol, which is consistent with its favorable transport in low-permeability cores. Four coreflood experiments in Texas Cream Limestone (TC Limestone) cores demonstrate the viability of PEO for EOR in low-permeability carbonate rocks. Single-phase experiments show 4 million g/mol PEO solutions transported through 18 and 28 md TC Limestone cores. Oil recovery experiments show 4 million g/mol PEO solutions transported and was more efficient than waterflooding in aged TC Limestone with favorable retention of 40 µg/g rock. An oil recovery experiment in an artificially fractured TC Limestone core improved oil recovery by a remarkable 15% considering the very large fracture-matrix permeability contrast (>7,000). These experimental results as well as other favorable properties of PEO reported in the literature indicate PEO should be considered for some EOR applications, especially in low-permeability reservoirs.

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.

Preparation of Fucoidan-Based Electrospun Nanofibers and Their Interaction With Endothelial Cells.

Sulfated polysaccharide fucoidan (FD) is widely applied in biomedical applications owing to its outstanding bioactivities. In addition to the biochemical features, the architecture of biomaterials plays a critical role in tissue repair and regeneration. Particularly, nanofibers have elicited great interest due to their extracellular matrix-like structure, high specific surface area, and favorable biological properties. Herein, chitosan-modified FD/ultra-high molecular weight polyethylene oxide (UHMWPEO) nanofibers are developed via green electrospinning and electrostatic interaction for studying their interaction with endothelial cells. The appropriate solvent is screened to dissolve FD. The electrospinnability of FD/UHMWPEO aqueous solutions is greatly dependent on the weight ratios of FD/UHMWPEO. The incorporation of UHMWPEO significantly improves the electrospinnability of solution and thermo-stability of nanofibers. Also, it is found that there is good miscibility or no phase separation in FD/UHMWPEO solutions. In vitro biological experiments show that the chitosan-modified FD/UHMWPEO nanofibers greatly facilitate the adhesion of endothelial cells and inhibit the attachment of monocytes. Thus, the designed FD-based nanofibers are promising bio-scaffolds in building tissue-engineered blood vessels.