Poly Ethylene Oxide Oligomers Research Articles

A method for deriving oligomers from sulfamide monomer and their application as electrolytes

This paper describes the development of a method of catalytic polymerization that was then applied to synthesize sulfate-based oligomers from sulfamide. Two molecules, copper triflate and copper acetate, catalyzed the formation of oligomers with diol monomers. Two oligomers were identified as products of the reactions. Oligomers with sulfate incorporated in the backbone proved to have an ability for ion diffusion. When the oligomers were doped with lithium salt, anion transportation was predominant, as shown by solid-state NMR. The lithium ion was found to be strongly bonded to the backbone, while the anion was highly mobile. To corroborate this finding, we conducted molecular dynamics (MD) simulations, which revealed the structural characteristics and static properties of two electrolytes containing LiTFSI and two different polyethylene oxide oligomers. Interactions between the anion and cation were analyzed through computation of the radial distribution function (RDF) and the spatial distribution function (SDF). Our findings indicate that while the anion presents weak interactions with the polymer chain, the cation interacts strongly with the oligomer backbone.

Sodium-ion electrolytes based on poly-ethylene oxide oligomers in dual-carbon cells: Anion size drives the charging behavior

Sodium-ion dual-carbon electrochemical cells are an environmentally friendly technology for energy storage purposes. In such systems, the migration of mutual ions in both electrodes is crucial for performance and determines the cell’s behavior. To investigate this effect, we have performed force-field molecular dynamics simulations of dual-carbon sodium-ion systems containing poly-ethylene oxide (PEO6) as the solvent and two different anions, bis(trifluoromethanesulfonyl)imide (TFSI−) and bis(fluorosulfonyl)imide (FSI−). We used a constant potential model that allows simulating the charging behavior of these cells at the potential differences, ΔΨ=1, 2, 3, and 5 volt (V). Our results showed that considering the neat solution, NaTFSIPEO6 exhibited the best transport properties. However, NaFSIPEO6 is a better choice of electrolyte to be employed in dual-carbon cells since it provides higher and faster charge accumulation. Structural analysis also confirmed that the system containing NaFSIPEO6 stored more ions inside their respective electrodes with Na+ cations having fewer molecules composing their first solvation shell. Overall, our findings suggest that the smaller molecular volume of the FSI− anion is the key factor to properly fill the positive electrode, and the NaFSIPEO6 combination is the best choice for electrolytes of dual-carbon cells.

Coarse-Grained Force Field for Polyethylene Oxide and Polyethylene Glycol Aqueous Solutions Based on a Polarizable Water Model

A new, accurate and transferable coarse-grained (CG) force field (FF) for polyethylene oxide (PEO) and polyethylene glycol (PEG) aqueous solutions based on a polarizable CG water (PCGW) model is developed in this work. A PCGW bead, which represents four water molecules, is modeled as two charged dummy particles connected by two constrained bonds to a central neutral particle; a PEO or PEG oligomer is modeled as a chain with repeated middle beads (PEOM) representing diether groups and two terminal beads (PEOT or PEGT) of a different type compared to PEOM. To describe nonbonded van der Waals interactions, a piecewise Morse potential with four tunable parameters is used. The force parameters are automatically and rigorously optimized by a meta-multilinear interpolation parameterization (meta-MIP) algorithm to simultaneously match multiple thermodynamic properties, including the density, heat of vaporization, vapor-liquid interfacial tension, and solvation free energy of the pure PEO or PEG oligomer bulk system as well as the mixing density and hydration free energy of the oligomer/water binary mixture. Additional thermodynamic and structural properties for longer PEO and PEG polymer aqueous solutions, such as the self-diffusion coefficient, radius of gyration, and end-to-end distance, are predicted to test the accuracy and transferability of this new CG FF. Based on the PCGW model, the presented FF optimization algorithm and strategy can be extended to more complex polyelectrolytes and surfactants.

High‐Performance Zinc‐Ion Battery Enabled by Tuning the Terminal Group and Chain Length of PEO‐based Oligomers

AbstractSide reactions and dendrite growth issues originated from free water seriously hamper the application of zinc‐ion batteries (ZIB). The electrolyte strategy of using a co‐solvent system has been proven to effectively improve the performance of ZIB. However, lack of thorough understanding of the co‐solvent structure on the performance of electrolytes hinders the rational design of co‐solvent electrolytes. Here, by studying how the terminal group and chain length of polyethylene oxide (PEO) based oligomers affect the electrochemical performance of ZIB, we obtained the optimized PEO oligomer structure and the underlying mechanism. As a result, the designed co‐solvent electrolyte enables the Zn|| NH4V4O10 full cell to gain a 98.5 % capacity retention over 9500 cycles at 10 A g−1. This work provides new insights into the inhibition of water‐related side reactions and further promote the development of electrolytes for ZIB and other metal batteries.

Structure formation and peculiarities of polymer composites based on the mixture of epoxy and polyethylene oxide oligomers

Structure formation and peculiarities of polymer composites based on the mixture of epoxy and polyethylene oxide oligomers

Weakly hydrated anions bind to polymers but not monomers in aqueous solutions.

Weakly hydrated anions help to solubilize hydrophobic macromolecules in aqueous solutions, but small molecules comprising the same chemical constituents precipitate out when exposed to these ions. Here, this apparent contradiction is resolved by systematically investigating the interactions of NaSCN with polyethylene oxide oligomers and polymers of varying molecular weight. A combination of spectroscopic and computational results reveals that SCN- accumulates near the surface of polymers, but is excluded from monomers. This occurs because SCN- preferentially binds to the centre of macromolecular chains, where the local water hydrogen-bonding network is disrupted. These findings suggest a link between ion-specific effects and theories addressing how hydrophobic hydration is modulated by the size and shape of a hydrophobic entity.

Hydrophobic versus Hydrophilic Interfacial Coatings on Silicon Nanoparticles Teach Us How to Design the Solid Electrolyte Interphase in Silicon-Based Li-Ion Battery Anodes

Herein, we evaluate the effect of covalently attached molecular coating hydrophobicity on the surface of the silicon nanoparticle (Si NP) active anode material for Li-ion batteries. The experiments are a means to identify the interfacial properties that help minimize electrochemical side reactions during cycling. Preformed coatings on the Si NP surfaces prior to electrode fabrication mimic the ionically conducting and electronically insulating properties of the solid electrolyte interphase (SEI). Hydrophilic oligomers such as polyethylene oxide (PEO) and other related structures are commonly identified as Li+-conducting components of the SEI. Here, we study the effect of such hydrophilic PEO versus hydrophobic alkyl molecular coatings on Si NP anode electrochemical performance. We also study the effect of the PEO oligomer length and the resulting effective thickness of the interfacial coating on the electrochemical performance. We find that PEO oligomers electrochemically isolate Si NPs when the PEO coating thickness approaches the electron tunneling distance of ∼2.5 nm. Surprisingly, the thickness of the PEO-based coatings has a negligible effect on their ability to minimize electrochemical side reactions as measured by Coulombic efficiency. These results reveal how the interfacial coating on silicon anode materials should differ from an operando-formed SEI layer and discuss design strategies for an ideal interfacial active material coating based on these results.

Novel Bulky Lithium Salts and Their Electrolytes for Safer Solid-State Lithium Metal Battery

In recent years, Lithium metal batteries (LMBs) have gained great interests thanks to their high capacity that can respond to the continuous increasing need for energy storage and device. The design and development of new solid-state electrolytes e.g. polymer based ones (SPEs) then became crucial towards intrinsically safer LMBs. A successful electrolyte candidate needs to fulfill several requirements such as high transference number (tLi +) and a compromise between two antagonist properties: conductivity and mechanical properties. Most researches focused on the synthesis of single-ion conducting electrolytes as a strategy to overcome these difficulties1,2. However, these materials often require complicated and delicate chemistry and their conductivity often remains low (σ < 10-5 S/cm at 60°C). An alternative promising route that received much less attention is the development of bulky Lithium salts with macroanion. The bulky anion reduces ion paring and salts aggregation and present negligible mobility compared to Lithium cation resulting in higher transference number3.In this work, we present a new macroanion based on Polyhedral Oligomeric Silsesquioxane (POSS) grafted with either polyethylene oxide oligomers (PEG) and/or Lithium sulfonyl (trifluoromethanesulfonyl) imide (LiTFSI) denoted as POSS-LiTFSI-PEG or POSS-LiTFSI respectively. Thus, SPE has been prepared with a reference high molecular weight polyethylene oxide at different OE/Li ratio from 10 to 25. This new concept of bulky multi-anion based on TFSI moieties allows a complete salt dissociation, an enhancement of the mechanical properties thanks to the presence of the inorganic POSS multi anions that play the role of nano fillers, and finally, a strong increase of the Li+ transference number (tLi+>0,55), which opens many perspectives. The cycling performance obtained in both Lithium symmetric cells and LMBs prototypes will be also presented.References(1) Bouchet, R.; Maria, S.; Meziane, R.; Aboulaich, A.; Lienafa, L.; Bonnet, J.-P. P.; Phan, T. N. T.; Bertin, D.; Gigmes, D.; Devaux, D.; et al. Single-Ion BAB Triblock Copolymers as Highly Efficient Electrolytes for Lithium-Metal Batteries. Nat. Mater. 2013, 12 (5), 452–457.(2) Zhang, H.; Li, C.; Piszcz, M.; Coya, E.; Rojo, T.; Rodriguez-Martinez, L. M.; Armand, M.; Zhou, Z. Single Lithium-Ion Conducting Solid Polymer Electrolytes: Advances and Perspectives. Chem. Soc. Rev. 2017, 46 (3), 797–815.(3) Chinnam, P. R.; Wunder, S. L. Polyoctahedral Silsesquioxane-Nanoparticle Electrolytes for Lithium Batteries: POSS-Lithium Salts and POSS-PEGs. Chem. Mater. 2011, 23 (23), 5111–5121. Figure 1

Solid Polymer Electrolytes Derived from Oligomeric Poly(ethylene oxide) Chain-Grafted Crosslinked Polystyrene Microspheres

A new class of lithium-ion conducting Solid Polymer Electrolytes (SPEs) has been derived from oligomeric Polyethylene Oxide (PEO)-grafted Cross-linked Polystyrene (XPS) microspheres containing one or two lithium sulfonamide moieties. The SPE containing Li:O mole ratio of 1:8 displayed excellent ionic conductivity (in excess of 10-4S/cm at 25ºC) and good electrochemical stability (4.3 volts versus Li/Li+). Thermal properties of these SPEs have also been investigated with Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA). These new SPEs possess amorphous character with a glass Transition Temperature (Tg) around 135ºC, and no significant thermal decomposition until 420ºC. Synthesis and characterization including surface morphologies of these SPEs are described.

Concentration dependence of the Flory-Huggins interaction parameter in aqueous solutions of capped PEO chains.

The dependence on volume fraction φ of the Flory-Huggins interaction parameter χwp(φ) describing the free energy of mixing of polymers in water is obtained by exploiting the connection of χwp(φ) to the chemical potential of the water, for which quasi-chemical theory is satisfactory. We test this theoretical approach with simulation data for aqueous solutions of capped PEO (polyethylene oxide) oligomers. For CH3(CH2-O-CH2)mCH3 (m = 11), χwp(φ) depends strongly on φ, consistent with experiment. These results identify coexisting water-rich and water-poor solutions at T = 300 K and p = 1 atm. Direct observation of the coexistence of these two solutions on simulation time scales supports that prediction for the system studied. This approach directly provides the osmotic pressures. The osmotic second virial coefficient for these chains is positive, reflecting repulsive interactions between the chains in the water, a good solvent for these chains.

Molar mass and temperature dependence of the thermodiffusion of polyethylene oxide in water/ethanol mixtures.

In this work, we study the molar mass dependence of the thermodiffusion of polyethylene oxide at different temperatures in ethanol, water/ethanol mixture (c(water) = 0.7), and water in a molar mass range up to M(w) = 180,000 g/mol. Due to the low solubility of polyethylene oxide oligomers in ethanol the measurements are limited up to M(w) = 2200 g/mol. The specific water/ethanol concentration 0.7 has been chosen, because at this weight fraction the thermal diffusion coefficient, D(T), of water/ethanol vanishes so that the system can be treated as a pseudo binary mixture. The addition of ethanol will degrade the solvent quality, so that we expect a change of the interaction energies between polymer and solvent. The analysis of the experimental data within a theoretical model shows the need of a refined model, which takes specific interactions into account.

Infrared, Raman and INS studies of poly-ethylene oxide oligomers

In the present paper the experimental findings obtained by different spectroscopic techniques on water mixtures of a protein model system, i.e. PolyEthylene Oxide (PEO), are reported. By increasing the polymerization degree m, the D-LAM spectral contribution shows a behavior of the centre frequency and of linewidth which tends to reach a constant value. Also the intramolecular OH stretching contribution, by increasing m, shows a shift which tends to flatten for polymers with molecular weight higher than Mw=600. These results can be connected with the oligomer–polymer transition, at m=13. When in aqueous solutions the D-LAM frequency increases towards the value corresponding to that of the crystal phase; similarly one observes also a sharpening of the D-LAM spectral contribution. These evidences suggest the presence of a more ordered conformation of PEO in water in respect to the melt phase.

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

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

Structure Formation of Ultrathin PEO Films at Solid Interfaces&#8212;Complex Pattern Formation by Dewetting and Crystallization.

The direct contact of ultrathin polymer films with a solid substrate may result in thin film rupture caused by dewetting. With crystallisable polymers such as polyethyleneoxide (PEO), molecular self-assembly into partial ordered lamella structures is studied as an additional source of pattern formation. Morphological features in ultrathin PEO films (thickness < 10 nm) result from an interplay between dewetting patterns and diffusion limited growth pattern of ordered lamella growing within the dewetting areas. Besides structure formation of hydrophilic PEO molecules, n-alkylterminated (hydrophobic) PEO oligomers are investigated with respect to self-organization in ultrathin films. Morphological features characteristic for pure PEO are not changed by the presence of the n-alkylgroups.

Molecular Dynamics Study of Aqueous Solution of Polyethylene Oxide: Critical Test of Force Field Models

Five differently proposed force fields are compared on their ability to reproduce experimental data of dilute aqueous solutions of polyethylene oxide (PEO). Solution densities, radii of gyration, radial distribution functions, self-diffusion coefficients, and also solvation free energies are evaluated in using atomistic Molecular Dynamics simulations. The chosen force fields are the three ones from Bedrov et al. [J. Phys. Chem. B 1998, 102, 996], including the original force field with the generic combining rule (GEN), one with empirical combination rule (EMP) and quantum chemistry based force field (QC). The other two force fields are the one from Cordeiro et al. [Macromolecules 2010, 43, 1583] (CZMP) and the CHARMM force field. The CZMP force field performs best in reproducing both thermodynamic and dynamic properties of the PEO dilute solution. The QC force field describes the chain dimension and hydrophilic behavior of PEO oligomers reasonably well and also the power-law exponent matches well with experimental results, but it overestimates the interaction strength between PEO and water resulting in slightly higher densities and slower mobilities for PEO oligomers in dilute solution. The CHARMM force field reproduces the densities and self-diffusion coefficients for PEO oligomers quite well, but it gives PEO a semi-hydrophobic character in dilute solution. The original force field, together with the EMP combining rule gives only the thermodynamic properties of PEO dilute solutions in a reasonable agreement with experimental data, but describes neither the thermodynamic nor the dynamic properties of PEO oligomers properly when it is used with the generic combination rule. Simulation results also reveal that CZMP, QC and CHARMM can qualitatively reproduce the solvation free energies for the ether unit in dilute aqueous solution. The influence of different water models on phase behavior of dilute PEO aqueous solution is indistinguishable in our simulations.

Preparation and characterization of composite electrolytes based on PEO(375)-grafted fumed silica

Recent developments in polymer electrolytes have focused on preparation of composites using nano/micron size ceramic particles such as SiO 2, TiO 2, Al 2O 3, BaTiO 3, and MgO. We report here the preparation and characterization of an all-solid state polyethylene oxide (PEO) composite electrolyte from PEO(375)–SiO 2, high molecular weight PEO (MW = 600 K) and LiClO 4 (O/Li = 16/1). Oligomeric PEOs, with ethylene oxide (EO) repeat units 6–9 (<MW> = 375 g/mol), were chemically grafted (~ 30 wt.%) to fumed silica (A380) using a trimethoxy PEO(375)-silane. The surface grafted PEO chains were disordered (no crystallization) and less mobile than the free chains, with the glass transition temperature ( T g) increasing from − 90 °C [PEO(375)-silane] to − 54 °C [PEO(375)–SiO 2]; addition of LiClO 4 (O/Li = 8/1) further raised T g to − 34 °C. Nanocomposite electrolytes with good dimensional stability were obtained by blending 14-wt.% PEO(375)–SiO 2 with semicrystalline PEO(600 K)/LiClO 4 (O/Li = 16/1). Conductivities ( σ) were 10 to 4 times greater [between 10 °C ( σ = 2.1 × 10 − 8 S/cm) and 40 °C ( σ = 1.1 × 10 − 5 S/cm), respectively] than for neat PEO(600 K) or for composite electrolytes having the same amount of native fumed silica, SiO 2. No conductivity improvements were observed above T m or for amorphous PEO(600 K)/LiClO 4 (O/Li = 8/1) with addition of SiO 2 or PEO(375)–SiO 2.

Sodalite ion exchange in polyethylene oxide oligomer solvents

Traditional aqueous methods of cation exchange in zeolites present complications for the exchange of catalytically important transition metal and rare earth ions. Ethylene oxide-based oligomers (polyethylene glycol, polyethylene glycol methyl ether, diglyme, tetraglyme, and polypropylene glycol) are being investigated as alternative media for zeolite ion exchange. Reactions using lithium as the exchanging species indicate that these solvents can be used successfully for ion exchange in hydrosodalite and dehydrated sodalite zeolites, enabling these reactions to be carried out in the absence of water. The oligomer solutions allow for the exchange of 88% to 99% of sodium ions for lithium ions after 3–5 exchange cycles at 100 °C in both hydrosodalite and dehydrated sodalite as determined by unit cell parameters and elemental analysis.

POSS Based Electrolytes for Rechargeable Lithium Batteries

A class of electrolytes based on polyethylene oxide (PEO)-functionalized polyhedral oligosilsesquioxanes [Q 8 M P E O ( n ) 8 or PEO(n)-POSS] and lithium salts was developed, where n = 2, 4, (8), (12.5) ethylene oxide units. Conductivities (a) of these highly branched, nonvolatile (375°C), viscous polymers (M w = 3000-5000 g/mol) were >10 - 3 S/cm at 50°C and >10 - 4 S/cm (LiClO 4 ) at room temperature (RT), comparable to conductivities of oligomeric PEOs (M w = 300-500). The T g values of Q 8 M P E O ( n = 2 , 4 , ) 8 /LiClO 4 were between -60 and -70°C, so that a at -20°C approached 10 - 6 S/cm. Strong self-supporting films (tensile strength 3.7 MPa) from 10% methyl cellulose and 90% Q 8 M P E O ( n = ) 8 /LiClO 4 had RT conductivities >10 - 5 S/cm.

Improvement of the emission properties of sol–gel silica matrices containing Eu 3+ in the presence of poly(ethylene glycol)-200

Composite organic/inorganic sol–gel matrices have been made with tetramethoxysilane and poly(ethylene glycol)-200, incorporating Eu 3+ ions. Polyethylene oxide oligomers match well with silica giving solid transparent gels. Europium ions are associated with the organic phase and they are protected from quenching mechanisms usually present in silica matrices. Thus, emission intensity and decay time increased and spectral bandwidth decreased in the presence of the oligomer. Increase of the decay time was also obtained with organic cationic dyes in the presence of the oligomer.

Composite Electrolytes Prepared from Fumed Silica, Polyethylene Oxide Oligomers, and Lithium Salts

The conductivity of solution electrolytes containing lithium salts (imide and triflate anions), poly(ethylene glycol), and mono‐ and dimethyl‐terminated poly(ethylene glycol) (Mw 200 to 400), and their corresponding composite electrolytes containing fumed‐silica particulates (0 to 20 weight percent) are reported. At room temperature the ionic conductivity is as high as for the composites studied, and they exhibit a gel‐like consistency but flow under shear. The electrochemical stability of the composites and compatibility with lithium metal were also examined. A large potential window (∼5.5 V) was found for Li imide‐based electrolytes. The passive film formed on lithium in contact with the composite electrolyte is relatively more stable and less resistive than that formed in contact with the parent solution electrolyte. Considering the additional advantages of processability and low volatility, these composites should be good candidate electrolytes for lithium and lithium ion batteries.