Poly Ethylene Oxide Dimethyl Ether Research Articles

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

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

Lithium transference number measurements and complex abilities in anion trapping triphenyloborane–poly(ethylene oxide) dimethyl ether–lithium trifluoromethanesulfonate composite electrolyte

In this paper we report the combined, positive effect of triphenyloborane (BPh 3) additive on conductivity and lithium cation transference numbers in poly(ethylene oxide) dimethyl ether (PEODME)–lithium trifluoromethanesulfonate (LiCF 3SO 3, LiTf) electrolytes. The transport mechanism is discussed on the basis of impedance measurements, restricted diffusion t + measurements, ionic association semi-empirical quantitative estimation and spectroscopic studies. A substantial increase in the lithium transference number values in triphenylborane enriched composite electrolytes was observed in comparison with the pure PEODME–LiCF 3SO 3 electrolyte. This effect is assisted by ionic conductivity enhancement.

Physico- and electrochemistry of composite electrolytes based on PEODME–LiTFSI with TiO 2

The effect of fumed TiO 2 fillers (pure and modified by H 2SO 4) on ionic conductivity of composite electrolytes based on poly(ethylene oxide) dimethyl ether (PEODME) oligomer ( M w = 500) doped with lithium bis-(trifluoromethanesulfonyl)imide LiN(CF 3SO 2) 2 (LiTFSI) are studied by differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FT-IR) and complex impedance methods. The electrochemical stability of the electrolytes in the potential range of 4 V versus Li electrode has been confirmed by voltammetric measurements. Li electrode reactions have been followed by means of impedance spectroscopy. The growth in time of the resistance of the interfacial (Li electrode–polymer electrolyte) layers was inhibited upon the addition of fillers.

The effect of type of the inorganic filler and dopant salt concentration on the PEO–LiClO 4 based composite electrolyte–lithium electrode interfacial resistivity

In the present paper the effect of the type of inorganic filler on the composite polymeric electrolyte–lithium electrode interfacial behavior is analyzed. Studies are performed in the wide LiClO 4 concentration range using poly(ethylene oxide)dimethyl ether (PEODME) as an electrolyte matrix. It is demonstrated that both the formation and the growth of the resistive layers at the polymer electrolyte–lithium electrode interface are determined by the salt concentration range and depend also on the type of the filler used. It is demonstrated that for salt concentrations lower than 10 −3 mol kg −1 or higher than 1 mol kg −1 addition of filler results in the suppression of the growth of the resistance of the interfacial layer. This effect has been related to an increase in lithium cation transference number observed in these salt concentration ranges in composite electrolytes compared to the pure PEODME–LiClO 4 analogues. The effect of the filler on conductivity, microstructure and thermal characteristic of electrolytes studied is also discussed.

The effect of salt concentration on the PEO–LiClO 4–lithium electrode interfacial resistivity

In the present paper the effect of the salt concentration on the formation and growth of the resistive layers at the polymer electrolyte–lithium electrode interface is analyzed. The studies are performed for poly(ethylene oxide)dimethyl ether (PEODME) doped with LiClO 4 electrolytes. It is shown that the rate of growth of the resistivity of interfacial layers depends on the concentration of the added salt and increases as the salt concentration increases. We have related this effect to the decrease in the lithium cation transference number and the increase in the fraction of ionic aggregates occurring with an increase in the salt concentration in polymeric electrolytes. The observed phenomena seem to be important from the viewpoint of application of polymeric electrolytes in lithium or (and) lithium ion batteries.

Determination of lithium transference number in PEO-DME–LiClO 4 modified with alumina powders of various surface acidity

The effect of alumina additives bearing various surface groups on conductivity and lithium cation transference numbers in poly(ethylene oxide) dimethyl ether (PEO-DME)–LiClO 4 electrolytes is examined. It is demonstrated that an increase in the conductivity and lithium transference number in composite electrolytes compared to pure PEO-DME–LiClO 4 electrolyte is observed in the limited salt concentration range. Both quantities seem to depend mostly on ionic species mobility. Also, their salt concentration dependence resembles that of viscosity of electrolytes studied. The conduction mechanism is discussed on the basis of conductivity, transference numbers and ionic association studies.

Ionic association in liquid (polyether–Al 2O 3–LiClO 4) composite electrolytes

The influence of surface-modified Al 2O 3 particles on the formation of different ionic aggregates in poly (ethylene glycol) methyl ether (PEGME)–LiClO 4 and poly (ethylene oxide) dimethyl ether (PEODME)–LiClO 4 electrolytes is discussed. Three independent methods have been used to estimate the fractions of free ions and ionic associates. The first two methods are based on the deconvolution of the FTIR 624 cm −1 and Raman 930 cm −1 perchlorate anion modes. The third method uses a Fuoss–Kraus semiempirical method involving the salt concentration dependence of ionic conductivity. Results are compared for two polyether systems to explain interactions in polymer electrolytes based on low molecular weight polyglycols. The temperature dependence of the fractions of ionic species is also analysed.

Connectivity-Altering Monte Carlo Simulations of the End Group Effects on Volumetric Properties for Poly(ethylene oxide)

Connectivity-altering Monte Carlo simulations have been used to study structure−property relationships of poly(ethylene glycol) (PEG) and poly(ethylene oxide) dimethyl ether (PEODME) using the recently developed transferable potentials for phase equilibria united atom (TraPPE-UA) ether and alkanol force fields. The combination of end-bridging and double-bridging Monte Carlo simulation techniques is shown to do a good job of equilibrating moderate to high molecular weight polymer melts. Results give excellent agreement between experiment and simulation for liquid densities at a variety of temperatures, pressures, and molecular weights. Comparisons are also made with experiment for structural properties, including the structure factor, chain mean squared end-to-end distance, and radius of gyration, showing good agreement with experiment. Moreover, a thorough microscopic analysis is performed on the different end group effects of PEG and PEODME, determining the excluded volume and liquid structure around the end groups, and linking these to their volumetric properties.

Composite Polymeric Electrolytes from the PEODME−LiClO4−SiO2 System

It is shown that the addition of fumed silica to polymer electrolytes results in the formation of gel-like polymer materials. Despite the quasi-solid structure of these composite systems, compared to the liquid base poly(ethylene oxide) dimethyl ether (PEODME)−LiClO4 electrolyte, an increase in conductivity is observed for several salt concentrations of composite systems compared to that of the PEODME−LiClO4 electrolytes. For other salt concentrations, the conductivities of the composite systems are slightly higher or at least comparable to that measured for the unmodified electrolyte. At the lowest salt concentrations (e.g., 10-5−10-4 mol/kg PEODME), the conductivities of the PEODME−LiClO4 electrolyte are higher. This increase in conductivity is related to the reduction in the fraction of ion pairs as revealed by FT-IR experiments and Fuoss−Kraus-type analyses of the salt concentration dependence of the ionic conductivity.

Cationization Processes in Matrix‐assisted Laser Desorption/Ionization Mass Spectrometry: Attachment of Divalent and Trivalent Metal Ions

In this paper, divalent and trivalent metal ions have been used as cationization reagents in matrix-assisted laser desorption/ionization (MALDI) experiments. Analytes studied include polyethylene glycol, polyethylene oxide dimethyl ether, cyclic polyethylene oxide and α-cyclodextrin. Independent of the valence of the metal ions and the nature of the analyte molecules studied, singly charged quasimolecular ions were generated in all cases. These quasimolecular ions were shown to be generated in different forms depending on the type of the di- or trivalent metal salts and the chemical properties of the analyte molecules. For Cu2+ ions, the quasimolecular ions were formed by the adduction of the reduced metal ions, i.e. Cu+. For Pb2+, Cd2+, Ba2+, Sr2+ and La3+ ions, singly charged quasimolecular ions were formed by adduction of the metal ions with either simultaneous deprotonation of the analyte molecule or adduction of an additional deprotonated matrix moiety onto the analyte molecule. Of these two choices, deprotonation of the analyte molecule is always preferred if labile protons, such as those in hydroxyl groups, are available in the analyte molecule. A model of ion formation from MALDI based on solid-state molecular pre-arrangement is used to account for the formation of such complex singly charged quasimolecular ions. © 1997 John Wiley & Sons, Ltd.

Cationization Processes in Matrix-assisted Laser Desorption/Ionization Mass Spectrometry: Attachment of Divalent and Trivalent Metal Ions

In this paper, divalent and trivalent metal ions have been used as cationization reagents in matrix-assisted laser desorption/ionization (MALDI) experiments. Analytes studied include polyethylene glycol, polyethylene oxide dimethyl ether, cyclic polyethylene oxide and α-cyclodextrin. Independent of the valence of the metal ions and the nature of the analyte molecules studied, singly charged quasimolecular ions were generated in all cases. These quasimolecular ions were shown to be generated in different forms depending on the type of the di- or trivalent metal salts and the chemical properties of the analyte molecules. For Cu2+ ions, the quasimolecular ions were formed by the adduction of the reduced metal ions, i.e. Cu+. For Pb2+, Cd2+, Ba2+, Sr2+ and La3+ ions, singly charged quasimolecular ions were formed by adduction of the metal ions with either simultaneous deprotonation of the analyte molecule or adduction of an additional deprotonated matrix moiety onto the analyte molecule. Of these two choices, deprotonation of the analyte molecule is always preferred if labile protons, such as those in hydroxyl groups, are available in the analyte molecule. A model of ion formation from MALDI based on solid-state molecular pre-arrangement is used to account for the formation of such complex singly charged quasimolecular ions. © 1997 John Wiley & Sons, Ltd.

Anion solvation effects in polymer-electrolytes: NaSCN and LiSCN in PEO-400 and in PEG-400

Infrared spectra in the “CN-stretch” region of the SCN − anion, for NaSCN and LiSCN, dissolved in polyethylene oxide dimethylether (PEO-400) of average molar mass 400, show dramatic differences from the infrared spectra of the same electrolytes dissolved in polyethylene oxide glycol (PEG-400) of average molar mass 400. The differences are attributed to anion solvation by the -OH end of the PEG polymers. Similar comparison of the molar refraction R of the two electrolytes dissolved in the two solvents, also shows dramatic differences in the values and concentration dependence of the R NaSCN and of R LiSCN between the two polymer solutions. These differences are also attributed to anion H-bonding solvation by PEG-400. The different molecular status of the above electrolytes in the two solvents, should be considered, when planning their use as ion transport media in polymer-electrolyte batteries.