Low Poly Ethylene Oxide Research Articles

Cationic cellulose nanofiber solid electrolytes: A pathway to high lithium-ion migration and polysulfide adsorption for lithium-sulfur batteries

Polyethylene oxide (PEO) solid electrolytes, acknowledged for their safety advantages over liquid counterparts, confront inherent challenges, including low ionic conductivity, restricted lithium ion migration, and mechanical fragility, notably pronounced in lithium‑sulfur batteries due to the polysulfide shuttling phenomenon. To address these limitations, we integrate a quaternary ammonium cation-modified cellulose (QACC) nanofiber, electrospun with cellulose acetate (CA) from recycled cigarette filters, into the PEO electrolyte matrix. The nitrogen atom within the quaternary ammonium group exhibits a pronounced affinity for polysulfide compounds, effectively curtailing polysulfide migration. Concurrently, Lewis acid-base interactions between quaternary ammonium groups and lithium salt anions facilitate the release of additional Li+, achieving a lithium-ion transference number 1.5 times higher than its pure PEO counterpart. Furthermore, the introduction of a larger trifluoromethanesulfonimide (TFSI) group on the QACC macromolecule (TFSI-QACC) disrupts the ordered arrangement of PEO macromolecules, resulting in a noteworthy enhancement in ionic conductivity, reaching 2.07 × 10−4 S cm−1 at 60 °C, thus addressing the challenge of low PEO electrolyte conductivity. Moreover, the nanofiber enhances the mechanical strength of the PEO electrolyte from 0.49 to 7.50 MPa, mitigating safety concerns related to lithium dendrites puncturing the electrolyte. Consequently, the composite PEO demonstrates exemplary performance in lithium symmetrical batteries, enduring 500 h of continuous operation and completing 100 cycles at both room and elevated temperatures. This integrated approach, transitioning from waste to wealth, adeptly addresses a spectrum of challenges in the efficiency of solid-state electrolytes, holding considerable promise for advancing lithium‑sulfur battery technology.

Low cost novel PEO based nano-composite for semiconductor and He–Ne lasers beam attenuation: Structural and optical properties

This paper reports the synthesis of low cost polyethylene oxide (PEO) based polymer nanocomposites (PNCs) for laser beam attenuation. The experimental investigations revealed the novel optical properties and bandgap reduction of PEO upon insertion of the Pb3O4 nanofiller. The changes in structural and optical properties of the prepared PNCs were explored using the X-ray diffraction (XRD) method and the ultraviolet–visible (UV–Vis). A broad shift of absorption is evidenced upon the addition of Pb3O4 nanofiller. The optical parameter, including absorption coefficient (α), linear refractive index (n), and dielectric loss (εi), were calculated. The optical band gap reduced significantly from 5.4 eV (neat PEO) to 1.8 eV for PEO doped with 9% Pb3O4. The direct and indirect electronic transitions in pure PEO and PEO: Pb3O4 PNCs were determined based on Tauc's model. The type of electron transition is specified with the assistance of εi spectra. The nonlinear optical parameter, including first-order susceptibility (χ1), third-order susceptibility (χ³), and nonlinear refractive index (n2), were studied. In addition, Laser beam attenuation characteristics for prepared PNCs samples were investigated using both semiconductor laser and He–Ne laser. The PEO: Pb3O4 PNCs significantly attenuated the laser power for both laser systems.

The effect of intracrystalline chain dynamics on melting and reorganization during heating in semicrystalline polymers

Using Fast Scanning Calorimetry we investigate the effect of intracrystalline chain dynamics on melting, recrystallization and crystal reorganization during heating, whereby we employ polyethyleneoxide (PEO) and polycaprolactone (PCL) as model polymers with and without such dynamics. We show that in PCL marginally stable crystallites form during isothermal crystallization, which melt immediately upon heating. During further heating continuous melting and recrystallization occurs. At low crystallization temperatures PEO shows a similar behavior, as the intracrystalline dynamics is strongly slowed down. However, during heating the intracrystalline chain dynamics becomes faster leading to fast lamellar thickening and increased thermal stability, until final melting occurs at some high temperature. Our observations demonstrate that melting, recrystallization, and reorganization are competing kinetic processes occurring during heating in semicrystalline polymers. These characteristics cannot be observed by conventional DSC due to low scanning rates and low accessible supercooling. The consequences for the Hoffman–Weeks analysis of polymer melting temperatures are discussed.

Fumed silica induces co-continuity across a wide composition range in immiscible polymer blends

We examine ternary blends composed of two immiscible polymers, polyisobutylene (PIB) and polyethylene oxide (PEO), and fumed silica particles which have strong affinity for the PEO. Samples with up to 10 vol% fumed silica and a wide range of PIB:PEO ratios were melt-blended and their morphology characterized. The unusual structure of fumed silica – which comprises 5–50 nm primary particles permanently bonded together into highly porous, fractal-like aggregates – strongly influences the morphology at all compositions. At relatively low PEO loadings, the PEO is absorbed into the pores within the fumed silica aggregates. The morphology consists of a network of interlocked particle aggregates bonded together by PEO. At higher PEO loadings, the PEO and the particles form a combined phase that is solid-like even at low fumed silica loadings. The morphology somewhat resembles a conventional co-continuous morphology where one phase is PIB and the other is a fumed silica-filled PEO. However, the microstructure is very irregular and the interface between the PIB and the PEO phase appears extremely rough on the scale of the primary particles. Morphologies with two percolating phases appear across almost the entire composition range examined. Compared to spherical fused silica particles examined previously, fumed silica affects the morphology of polymer blends at far lower particle loadings, and greatly widens the range of co-continuity.

Direct Assessment of Tube Dilation in Entangled Polymers.

A key ingredient within theories focusing on the rheology of entangled polymers is the way how the topological constraints of an entangled chain are lifted by unconstrained segments, i.e., how the constraining tube is dilated. This important question has been addressed by directly measuring the tube diameter d at the scale of the tube by neutron spin echo spectroscopy. The tube diameter d and plateau modulus G_{N}^{0} of highly entangled polyethylene oxide (PEO) chains of volume fraction c that are diluted by low molecular PEO show a concentration dependence d∝c^{a/2} and G_{N}^{0}∝c^{1+a} with an exponent a close to 4/3. This result allows the clear discrimination between different theoretical models that predict 4/3 or other values between 1 and 2 and provides an important ingredient to tube model theories.

Electrochemical Capacitor Electrodes Based on High-Purity Eelectrospun Polyaniline and Polyaniline-Carbon Nanotube Nanofibers

Freestanding, binder-free supercapacitor electrodes based on high purity polyaniline (PANI) nanofibers were fabricated using electrospinning. To prevent jet break-up and to enable successful electrospinning of high-purity PANI nanofibers (93 wt%), large molecular weight poly (ethylene) oxide (PEO) was added to the PANI solution as a carrier polymer. The high molecular weight of PEO allowed us to impart adequate entanglements (critical for electrospinning) at a low PEO. Scanning electron microscope (SEM) and Brunner-Emmet-Teller (BET) analysis were used to examine the morphology and porosity of the nanofibers. The PANI nanofibers, with an average diameter of 678±54 nm, were characterized by micro-pores on their surfaces possibly due to evaporative cooling during electrospinning. These pores, with the most common size of 1.6 nm, resulted in a specific surface area of 20 m2 g-1. To enhance electrical conductivity as well as structural stability of the resultant electrodes, carbon nanotubes (CNTs) were added to the PANI/PEO solution. The PANI/CNT nanofibers exhibited an average diameter of 528±50 nm. The slight decrease in diameter is attributed to introduction of highly conductive CNTs in the polymer solution which leads to higher charge density and therefore greater jet elongation. Transmission electron microscope (TEM) showed excellent distribution of CNTs within the nanofibers. The electroactivity of these freestanding PANI and PANI/CNT nanofibers electrodes were examined using cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy. Specific capacitance of 308 and 385 F g-1 at 0.5 A g-1 were achieved for PANI and PANI/CNT based electrodes, respectively. Both electrodes showed excellent rate capability when cycling voltammetry (CV) scan rate was varied from 5 to 100 mVs-1 and current density was increased to 10 A g-1. Areal capacitances of 1.15 and 1.37 F cm-2 were obtained for PANI and PANI-CNT, respectively, when electrode loading was increased with negligible loss in gravimetric specific capacitance. Capacitance retention of 70 and 82% were observed for PANI and PANI/CNT electrodes after 1000 cycles, respectively, indicating enhanced electrochemical performance with incorporation of only 12 wt% of CNT to the PANI nanofibers. The promising electrochemical performance of the fabricated electrodes, we believe, stems from the porous 3-D electrode structure characterized by nonwoven interconnected nanostructures. The interconnected nanofiber network facilitates efficient electron conduction whereas the inter- and intra-fiber porosity enable excellent electrolyte penetrations within the polymer matrix hence quick ions transport to active sites. Moreover, the freestanding electrodes avoid potential structural damage most likely encountered when preparing paste for electrochemical testing in the “conventional” way. Simotwo, S; Delre, C and Kalra, V. Supercapacitor Electrodes Based on High-Purity Electrospun Polyaniline and Polyaniline-Carbon Nanotube Nanofibers, submitted (2016) Figure 1

Reducing the content of carrier polymer in pectin nanofibers by electrospinning at low loading followed with selective washing

Nanofibers of natural polymers represent an essential class of materials in biomedicine. Pectin is a plant-sourced anionic polysaccharide widely used in food products and biomedicine owning to its abundance, biocompatibility and inherent bioactivity. However, current electrospun pectin nanofibers are suffered from high content of carrier polymer, which may lead to low integrity and mechanical strength as well as in vivo toxicity. We report here a strategy to reduce the content of carrier polymer, polyethylene oxide (PEO) in our study, in pectin nanofibers, via electrospinning at low loading followed with selective washing. With improved electrospinning condition, we first enabled electrospinning of pectin nanofibers at low PEO loading. Then the PEO was removed by washing with a selective solvent to give pectin nanofibers containing only 1.5% PEO. The strategy was versatile to pectins from various sources and of various degree of esterification. The pectin nanofibers exhibited Young's modulus as high as 358.5MPa. In view of their rich bioactivity, the pectin nanofibers of low content of carrier polymer are promising materials for a wide range of biomedical applications.

Preparation and properties of monomer casting nylon-6/PEO blend prepared via in situ polymerization

A series of MC nylon-6/ polyethylene oxide (PEO) blends were prepared via in situ polymerization. It was found that addition of PEO delayed the polymerization process of caprolactam. The apparent activation energy and pre-exponential factor increased, indicating that the polymerization reaction became difficult with increasing PEO content. The stress–strain curves of the blends presented strain hardening behavior and increasing elastic deformation stress plateau at low PEO content. Nonisothermal DSC and XRD tests indicated that addition of PEO led to a decrease of the crystallization ability of the nylon-6 matrix by reducing crystal grain size and crystallinity, whereas the crystallization ability of the PEO phase was improved. No co-crystal formed between the two phases. PEO with low content only existed as amorphous state, while with increasing PEO content, PEO can crystallize gradually, forming interfibrillar segregation first, and then forming interspherilute segregation of the blend independently. By addition of PEO, the fracture surface of the blend became rough, displaying character of tough fracture. The interface between nylon-6 phase and PEO phase was diffused, and the nylon-6 matrix around the PEO particles presented fibrous structure, indicating the good compatibility between them. The toughening mechanism of the blend corresponded to the crazing-shear banding mechanism. POLYM. ENG. SCI., 55:589–597, 2015. © 2014 Society of Plastics Engineers

The thermodynamic and structural rules governing the solubilization of anthracene in aqueous solutions of polyethylene oxide

The influence of the temperature and concentration of aqueous solutions of polyethylene oxide (PEO) on the UV absorption spectrum of anthracene (Ant) was studied. The enthalpy and entropy factors of dynamic equilibrium of Ant molecules between the aqueous phase, in which Ant molecules form hydration capsules around them, and polymer-chain capsule structures responsible for bonding between Ant and macromolecules were determined. It was shown by the method of molecular mechanics that the solubilization of Ant molecules by dissolved PEO involves the formation of capsules of polymer chain units around Ant molecules. A phenomenological equation of equilibrium solubilization was obtained and theoretically substantiated. At low PEO concentrations, this equation transformed into the Sechenov solubility law, which described the equilibrium solubilization of Ant molecules no less successfully than the well-known equation for the solubilization of such hydrophobic hydrocarbons as naphthalene and diphenyl.

Adsorption of poly(ethylene oxide) at the air/water interface: A dynamic and static surface tension study

The adsorption of polyethylene oxide (PEO) homologues in a wide range of molecular weight (from M PEO = 200 to 10 6) at the air/aqueous solution interface was investigated by dynamic and static surface tension measurements. An approximate estimate for the lower limit of PEO concentration was given at which reliable equilibrium surface tension can be determined from static surface tension measurements. It was shown that the observed jump in the earlier published σ – lg ( c PEO ) curves is attributable to the nonequilibrium surface tension values at low PEO concentrations. The adsorption behavior of short chain PEO molecules ( M PEO ⩽ 1000 ) is similar to that of the ordinary surfactants. The estimated standard free energy of PEO adsorption, Δ G 0 , increases linearly with the PEO molecular weight until M PEO = 1000 . In this molecular weight range, Δ G 0 was found to be approximately the fifth of the hydrophobic driving force related to the adsorption of a surfactant with the same number of methylene groups. In the case of the longer chain PEOs the driving force of adsorption is so high that the adsorption isotherm is near saturation in the experimentally available polymer concentration range. Above a critical molecular weight the PEO adsorption reveals universal features, e.g., the surface tension and the surface density of segments do not depend on the polymer molecular weight.

The ionic conductive property of sulfonated polyethylene oxide polyurethane ionomers

AbstractA series of lithium and sodium salts of sulfonated polyethylene oxide (PEO) polyurethane ionomers in different levels of ionization were prepared. It has been found that this material is a new type of ionic conductive polymer, characterized by a single‐ion transport mechanism and good mechanical properties. The ionization level significantly influences the ionic conductivity of the samples. When the mole ratio of the metal ion and ether oxygen atom is about 0.05, the ionomers exhibit maximum cationic conductivity. An optimal cationic conductivity of 1.0 × 10−5 S/cm is obtained at about 70°C without any addition of organic plasticizer. The conductivity increases apparently when propylene carbonate and low MW PEO are added to the polyurethane ionomer. © 1995 John Wiley & Sons, Inc.

Development and evaluation of a new polymeric material for small caliber vascular prostheses

Polyethylene oxide (PEO), because of its low levels of protein and cellular adsorption, may provide a suitable coating for synthetic small caliber vascular prostheses. PEO/polysiloxane networks were synthesized via an acid-catalyzed epoxy/hydroxyl crosslinking reaction and used to produce conduits with a 4-mm internal diameter. Three networks with nominal PEO molecular weights of 2000, 8000, and 20,000 and all 65% PEO by weight were studied. Blood compatibility was assessed by measuring 111In-platelet and 125I-fibrinogen deposition in a baboon ex vivo shunt, over a 1-hr time period and at a flow rate of 50 ml/min. Differences in material performance were noted particularly after the initial 30-min blood contact period. Materials in the mid and high PEO molecular weight range (8000 and 20,000) had significantly lower levels of platelet adsorption than networks of low PEO molecular weight (2000) at 30 min ( P < 0.005) and 60 min ( P < 0.05). The lowest level of platelet deposition was noted on networks of high PEO molecular weight (20,000). During the observation period, platelet accumulation on this surface was less than one platelet per 1000 μm 2. Platelet deposition on Gore-Tex was two and three orders of magnitude greater than that on the high molecular weight PEO material at 30 and 60 min, respectively ( P < 0.001). Fibrinogen adsorption was also lower on materials of mid and high PEO molecular weights, when compared with low molecular weight networks ( P < 0.05) and Gore-Tex ( P < 0.05). Scanning electron micrographs confirmed these observations. Overall, platelet and fibrinogen depositions are low for PEO networks, particularly for materials of high PEO molecular weight. This latter observation may be related to increased surface molecular mobility and a relative enhancement of PEO content at the blood-material interface.