Poly Ethylene Glycol Dimethyl Ether Research Articles

New Approach to the Reduction of Recombination in Dye-Sensitised Solar Cells via Complexation of Oxidised Species

Although dye-sensitised solar cells (DSSCs) have received great attention as low-cost and clean energy conversion devices, their conversion efficiency still lags behind that of inorganic solar cells. One of the reasons is due to the recombination of injected electrons with the oxidised species of the redox couple that are present in the electrolyte near the surface of the bare TiO2 particles. While most research has focused on blocking the bare surface of the TiO2 nanoparticles, we have introduced a new approach that can directly reduce the concentration of the oxidised species of the redox couple present in the electrolytes through complex formation. Recombination was reduced by the addition of cyclodextrins (CDs) to a polyethyleneglycol dimethyl ether (PEGDME) electrolyte containing iodide/triiodide redox couples that can form a complex with the triiodide. Experimental and theoretical investigation of the complex formation between triiodide and the CD in PEGDME matrix was performed. Increase in total power conversion efficiency was achieved using the alpha-CD as an additive in a low volatile PEGDME based electrolyte. Electrochemical impedance spectra and intensity modulated photovoltage spectroscopy measurements showed that the increase in the short-circuit current density is due to the suppression of surface recombination by the complex formation between the CDs and the triiodide ions.

Some Insight into Stability of Amorphous Poly(ethylene glycol) Dimethyl Ether Polymers Based on Molecular Dynamics Simulations.

Poly(ethylene glycol) dimethyl ether (PEGDME) polymers are widely used as drug solid dispersion reagents. They can cause the amorphization of drugs and improve their solubility, stability, and bioavailability. However, the mechanism about why amorphous PEGDME 2000 polymer is highly stable is unclear so far. Molecular dynamics (MD) simulation is a unique key technique to solve it. In the current work, we systematically investigate structure, aggregate state, and thermodynamic and kinetic behaviors during the phase-transition processes of the PEGDME polymers with different polymerization degree in terms of MD simulations. The melting and glass-transition temperatures of the polymers are in good agreement with experimental values. The amorphous PEGDME2000 exhibits high stability, which is consistent with the recent experiment results and can be ascribed to a combination of two factors, that is, a high thermodynamic driving force for amorphization and a relatively low molecular mobility.

Enhanced performance of a novel gel polymer electrolyte by dual plasticizers

In this contribution, polyethylene glycol dilaurate (PEGDL) is synthesized and adopted as the physical cross-linking agent to enhance the performance, especially the mechanical property of the gel polymer electrolytes (GPEs). With polyethylene glycol dimethyl ether (PEGDME) as the main plasticizer and PEGDL as the secondary plasticizer, several gel polymer electrolytes based on a copolymer of methoxy-poly(ethylene glycol) methacrylate (MPEGM) and hexadecal-poly(ethylene glycol) methacrylate (HPEGM) are prepared by UV radiation curing. The relationship between the composition of the GPE and the physical properties, e.g., thermal property, mechanical property and ionic conductivity, is investigated. The lithium ion transference number, lithium/GPE interfacial property and charge–discharge performance of the lithium polymer cell based on the physically cross-linked GPE are studied. The gel polymer electrolyte prepared with the optimum composition exhibits excellent mechanical properties and a relatively high ionic conductivity (8.2 × 10−4 S cm−1 at 30 °C). A coin cell Li/GPE/LiFePO4, shows a discharge capacity 152 mAh g−1 and 163 mAh g−1 when cycled at 30 °C and 50 °C, respectively, under a current density of 0.1 C.

System modeling of exergy recuperated IGCC system with pre- and post-combustion CO2 capture

This paper describes a novel advanced integrated gasification combined cycle (A-IGCC) for heat integration technology with carbon dioxide (CO2) capture. The feature of this system is an exergy recuperation in which the exhaust heat from the gas turbine and the steam are used as gasifying agents, providing higher cold gas efficiency. A-IGCC can achieve higher plant thermal efficiency with much less energy/exergy loss compared to a conventional IGCC. Two CO2 capture options, (i) pre-combustion by a mixture of dimethyl ethers of polyethylene glycol (DEPG) and (ii) post-combustion by monoethanolamine (MEA), were assessed to compare the total plant performance and necessary technologies for future implementation. A-IGCC maintained a higher plant performance than IGCC, delivering sufficient energy in the gasifier for the autothermal reaction. A higher efficiency was obtained in IGCC with pre-combustion capture, with a thermal efficiency of 33.2% compared to 43% without capture. In A-IGCC, however, the higher efficiency was obtained with post-combustion capture, with a thermal efficiency of 38.5% compared to 50.6% without capture. Adding a CO2 removal unit with 81 mol% CO2 absorption imposed the plant efficiency loss of 9.9–15.2%. The surplus heat at lower temperature was left unused when pre-combustion capture was used for the A-IGCC plant model, which resulted in a large reduction in plant efficiency.

The electrochemical properties of high-capacity sulfur/reduced graphene oxide with different electrolyte systems

The lithium/sulfur battery is a promising electrochemical system with high capacity, which is well-known to undergo a complex multistep reaction during the discharge process. Two types of electrolytes including poly(ethylene glycol) dimethyl ether (PEGDME)-based and 1,3-dioxolane (DOL)/dimethoxyethane (DME)-based electrolytes were investigated here. Furthermore, LiNO3 additive was introduced into the electrolyte in order to effectively eliminate the overcharge effect. The lithium sulfur battery with 1.0 M LiN(CF3SO2)2 in PEGDME with 0.1 M LiNO3 shows highly stable reversible capacity of 624.8 mAh g−1 after 200 cycles and improved average coulombic efficiency of 98%.

Effect of temperature on volumetric and transport properties of ternary poly ethylene glycol di-methyl ether 2000 + poly ethylene glycol 400 + water and the corresponding binary aqueous solutions: Measurement and correlation

The density, speed of sound and viscosity values of {poly ethylene glycol di-methyl ether 2000 (PEGDME2000)+poly ethylene glycol 400 (PEG400)+water}, ((PEGDME2000)+water) and ((PEG400)+water) solutions have been measured at T=(293.15, 298.15, 303.15, 308.15, and 313.15)K. From these measurements, values of the excess molar volume (VmE), excess molar isentropic compression (Ks,mE), excess Gibbs free energy of activation of viscous flow (G*E) and deviation of viscosity (Δη) were calculated. Expressions for VmE and Ks,mE of polymer solutions were obtained by the modified Wilson model for binary and multi-component polymer solutions. The necessary expression for Ks,mE of the polymer NRTL model was also obtained for multi-component polymer solutions. These expressions were used to fit the experimental VmE and Ks,mE data of the investigated systems. Furthermore, the Eyring-modified Wilson and Eyring-NRTL models have been used to correlate the viscosity values of binary and ternary solutions. The apparent specific volumes at infinite dilution values for the binary and ternary solutions were also determined from the density data at dilute range. These values were used to obtain some information regarding the segment–solvent and segment–segment interactions.

A Composite Polymer Electrolyte Protect Layer between Lithium and Water Stable Ceramics for Aqueous Lithium-Air Batteries

The electrochemical properties of a composite polymer electrolyte consisting of polyethylene oxide (PEO)-lithium trifluoromethanesulfonylimide (LiTFSI) and poly(ethylene glycol) dimethyl ether (PEGDME) were examined as a protective layer between a lithium metal electrode and water-stable lithium ion-conducting glass ceramic of Li1.35Ti1.75Al0.25P0.9Si0.1O12. The lithium ion transport number was doubled and the lithium ion conductivity was enhanced from 1.3 × 10−4 for PEO18LiTFSI to 3.8 × 10−4 S cm−1 at 60°C by the addition of 18 wt% PEGDME. The lithium stripping and plating over-potentials for the Li/PEO18LiTFSI-18 wt% PEGDME/LTAP/1M LiCl aqueous solution/Pt, air cell were 0.3 and 0.25 V at 1.5 mA cm−2 and 60°C, respectively. Steady charge and discharge potentials for the Li/PEO18LiTFSI-18 wt% PEGDME/LTAP/10 M LiCl-4 mM LiOH/Pt air cell were observed for 12 h at 1.0 mA cm−2 and 60°C without short circuiting of the cell. Lithium dendrite formation at the lithium/PEO18LiTFSI interface was suppressed by the addition of PEGDME.

Ammonia Escape Inhibited by NHD in the Process of Carbon Capture Using Ammonia Solution

Using ammonia solution to absorb CO2 from flue gas is expected to achieve low cost and high efficiency; however, ammonia escape during CO2 absorption limits the application of this technique. In this work, we investigated the inhibitory effect of polyethylene glycol dimethyl ether (NHD) on ammonia escape in bubbling absorption using ammonia solution. Various NHD and ammonia concentrations on ammonia escape are considered. Results show that NHD significantly inhibits on ammonia escape and enhances removal of CO2 at the same time as well. The amount of escaping ammonia was reduced by 24.9% when 5% NHD was used. The study has important implications for application of the ammonia absorption method in carbon capture.

Dielectric and refractive index measurements for the systems 1-pentanol + 2,5,8,11,14-pentaoxapentadecane, or for 2,5,8,11,14-pentaoxapentadecane + octane at (293.15–303.15) K

Relative permittivities, ɛr, and refractive indices, nD, have been measured at (293.15–303.15)K, for the mixtures 1-pentanol+2,5,8,11,14-pentaoxapentadecane (TEGDME) or TEGDME+octane. These data have been used, together with density measurements available in the literature, to calculate the correlation factors, gK, according to the Kirkwood–Fröhlich equations. The curves of the deviations of ɛr from the ideal behaviour, Δɛr, of the 1-pentanol+TEGDME system are shifted to high mole fractions of the alcohol, and show a rather large minimum. The shape of the Δɛr curves of methanol+TEGDME or +polyethylene glycol dimethyl ether 250 (PEG-250) mixtures is similar. This reveals that polyethers can break the alcohol self-association even at high alkanol concentrations. The higher Δɛr values of the methanol solutions are ascribed to large self-association of this alcohol. The Δɛr curves of the 1-pentanol+dibutyl ether (DBE) system are nearly symmetrical, and the Δɛr values are higher than those of the corresponding TEGDME mixture. This indicates that effects related to the alcohol self-association are much more relevant in the DBE system. These findings are supported by gK and molar polarization data. Values of molar refraction of 1-pentanol systems reveal that dispersion forces become more important in the sequence: octane<DBE<TEGDME. Such forces are also more relevant in the 1-pentanol+TEGDME system than in the methanol+TEGDME solution. The comparison of ɛr and gK data for TEGDME or DBE+octane mixtures shows than the polyether is a more structured liquid.

Ether Based Electrolyte, LiB(CN)4 Salt and Binder Degradation in the Li–O2 Battery Studied by Hard X-ray Photoelectron Spectroscopy (HAXPES)

Li–O2 cells composed of a carbon cathode containing an α-MnO2 nanowire catalyst and a Kynar (PVDF-HFP) binder were cycled with different electrolytes containing 0.5 M LiB(CN)4 salt in polyethylene glycol dimethyl ether (PEGDME) or tetraethylene glycol dimethyl ether (Tetraglyme) solvents. All cells exhibited fast capacity fading. To explain this, the surface chemistry of the carbon electrodes were investigated by synchrotron based hard X-ray photoelectron spectroscopy (HAXPES) using two photon energies of 2300 and 6900 eV. It is shown that the LiB(CN)4 salt and Kynar binder were degraded during cycling, forming a layer composed of salt and binder residues on the cathode surface. The degradation mechanism of the salt differed in the two tested solvents and, consequently, different types of boron compounds were formed during cycling. Larger amounts of the degraded salt was observed using Tetraglyme as the solvent. With a nonfluorined Li-salt, the observed formation of LiF, which might be a reason for the observed blockage of pores in the cathode and for the observed capacity fading, must be due to Kynar binder decomposition. The amount of LiF formed in the PEGDME cell was larger than that formed in the Tetraglyme cell. The results indicate that not only the electrolyte solvent, but also electrolyte salt as well as the binder used for the porous cathode must be carefully considered when building a successful rechargeable Li–O2 battery.

Vapour–liquid equilibrium of ternary aqueous polymer solutions containing polyethylene glycol and polyethylene glycol dimethyl ether at different temperatures

Water activities of ternary aqueous polymer solutions containing polyethylene glycol and polyethylene glycol dimethyl ether were determined experimentally using an improved isopiestic method at T=298.15, 308.15 and 318.15K. The applicability of the modified Wilson model was tested for correlation of water activity of ternary polymer–polymer–solvent solutions studied in this work and others studied previously. The parameters determined in binary solutions were used in the calculation of water activity of ternary polymer solutions.

Shear and conductivity relaxations of lithium ion electrolytes in polyethyleneglycol dimethyl ethers

The frequency-dependent shear viscosity and electric conductivity of the solution of lithium perchlorate in tetraglyme (TEG) and polyethyleneglycol dimethyl ether (P10, average molecular weight is 500) are measured and compared with each other. The shear viscosity of neat P10 shows a relaxation around 100MHz, and its relaxation amplitude increases with the concentration of the salt, which can be ascribed to the large-scale intramolecular mode of a solvent molecule. In addition, another relaxation appears at 10MHz after the addition of the salt. No relaxation is found in the shear viscosity of TEG solution below 200MHz. The conductivity of P10 solution does not show any dispersion around 10MHz, which indicates that the ionic mobility is decoupled from the relaxation process at 10MHz. Although a relaxation of conductivity is found around 100MHz in P10 solution, the relaxation frequency increases with concentration, while the relaxation frequency of the shear viscosity little depends on the concentration. These two relaxations are therefore assigned to different mechanisms, indicating that the ionic mobility is decoupled also from the large-scale intramolecular mode of a chain. The comparison between the conductivity spectra of P10 and TEG solution shows that the mobility of the local mode of solvent is the determining factor of the ionic mobility.

Salting-In and Salting-Out of Water-Soluble Polymers in Aqueous Salt Solutions

To obtain further experimental evidence for the mechanisms of the salting effect produced by the addition of salting-out or sating-in inducing electrolytes to aqueous solutions of water-soluble polymers, systematic studies on the vapor-liquid equilibria and liquid-liquid equilibria of aqueous solutions of several polymers are performed in the presence of a large series of electrolytes. Polymers are polyethylene glycol 400 (PEG400), polyethylene glycol dimethyl ether 250 (PEGDME250), polyethylene glycol dimethyl ether 2000 (PEGDME2000), and polypropylene glycol 400 (PPG400), and the investigated electrolytes are KCl, NH(4)Cl, MgCl(2), (CH(3))(4)NCl, NaCl, NaNO(3), Na(2)CO(3), Na(2)SO(4), and Na(3)Cit (tri-sodium citrate). Aqueous solutions of PPG400 form aqueous two-phase systems with all the investigated salts; however, other investigated polymers form aqueous two-phase systems only with Na(2)CO(3), Na(2)SO(4), and Na(3)Cit. A relation was found between the salting-out or sating-in effects of electrolyte on the polymer aqueous solutions and the slopes of the constant water activity lines of ternary polymer-salt aqueous solutions, so that, in the case of the salting-out effect, the constant water activity lines had a concave slope, but in the case of the salting-in effects, the constant water activity lines had a convex slope. The effect of temperature, anion of electrolyte, cation of electrolyte, and type and molar mass of polymers were studied and the results interpreted in terms of the solute-water and solute-solute interactions. The salting-out effect results from the formation of ion (specially anion)-water hydration complexes, which, in turn, decreases hydration, and hence, the solubility of the polymer and the salting-in effect results from a direct binding of the cations to the ether oxygens of the polymers.

Lithium-sulfur cell with combining carbon nanofibers–sulfur cathode and gel polymer electrolyte

In this paper we report a novel lithium-sulfur cell, which is characteristic of a unique combination of carbon nanofibers–sulfur cathode and gel polymer electrolyte (GPE). In particular, the carbon nanofibers for the cathode and the poly(acrylonitrile)/poly(methyl methacrylate) (PAN/PMMA) membrane for the GPE are prepared by electrospinning technique. The GPE consists of electrospun PAN/PMMA membrane and 1 mol kg−1 lithium bis(trifluoromethylsulfonyl)imide in N-methyl-N-butylpiperidinium bis(trifluoromethanesulfonyl)imide (PPR14TFSI) and poly (ethylene glycol) dimethyl ether (PEGDME). The membrane and cell performances are investigated by scanning electron spectroscopy, cyclic voltammetry and electrochemical impedance spectroscopy. It is found that the cell using the GPE based on PAN/PMMA membrane and PPR14TFSI-PEGDME (1:1) exhibits the largest discharge capacity and the best cycle durability. The discharge capacity of this cell remains at 760 mA h g−1 after 50 cycles. This new sulfur/electrolyte system combines the advantages of the carbon nanofibers that provide an effective conduction path and network-like structure, and the GPE that suppresses the dissolution of the intermediate products generated during the discharge process. The ratio of PPR14TFSI to PEGDME affects the ionic conductivity of the GPE, the stability of the sulfur electrode and the compatibility of lithium electrode with the GPE.

High-Pressure Solubility of Methane (CH4) and Ethane (C2H6) in Mixed Polyethylene Glycol Dimethyl Ethers (Genosorb 1753) and Its Selectivity in Natural Gas Sweetening Operations

The solubility of methane (CH4) and ethane (C2H6) in a mixture of polyethylene glycol dimethyl ethers (Genosorb 1753) was measured at (298.15, 313.15, and 333.15) K and at pressures up to 7700 kPa using a Jerguson equilibrium cell. The solubility data of CO2 and light hydrocarbons (CH4 and C2H6) in Genosorb 1753 were compared with the solubility in other physical solvents. The results were correlated with the Peng–Robinson equation of state (PR-EOS), and the interaction parameters are reported. Among the activity coefficient models, the Non-Random Two Liquid Theory (NRTL) model fitted the data well with an absolute average deviation of 6 %. Henry’s Law constants (HCH4 and HC2H6) and the excess properties (excess Gibbs free energy (GE), excess entropy (SE), and excess enthalpy (HE)) of the liquid mixture were predicted at each temperature using the NRTL activity coefficient model over the full range of composition. The enthalpy of solution and the partial molar enthalpy of mixing for all gases were determi...

Pre-combustion carbon dioxide capture by gas–liquid absorption for Integrated Gasification Combined Cycle power plants

Among various configurations of fossil fuel power plants with carbon dioxide capture, this paper focuses on pre-combustion capture technology applied to an Integrated Gasification Combined Cycle power plant using gas–liquid absorption. The paper proposes a detailed study and optimization of plant design (column height and packed dimensions) with CO2 capture process using different solvents as: aqueous solutions of alkanolamine, dimethyl ethers of polyethylene glycol, chilled methanol and N-Methyl-2-pyrolidone. By developing simulations in Aspen Plus, the following performance results of these physical and chemical solvents, mentioned above, are discussed: overall energy consumption (power consumption, heating and cooling agent consumption), CO2 specific emissions, net electric power output and plant efficiency. The paper presents as well, the total investment capital cost of an IGCC coal mixed with biomass (sawdust) power plant generating 425–450MW net electricity with (70% CO2 capture, 80% CO2 capture and 90% CO2 capture) and without pre-combustion CO2 capture.Simulation results show that for evaluated solvents for CO2 capture, the physical solvent, dimethyl ethers of polyethylene glycol, is more energy efficient that the other physical and chemical solvents investigated. Regarding the economic study, implementation of pre-combustion CO2 capture on IGCC plant, using dimethyl ethers of polyethylene glycol, leads to an increase of the capital cost with about 19.55% for 70% CO2 capture, 20.91% for 80% CO2 capture and 22.55% for 90% CO2 capture.

CO2-selective membranes for hydrogen purification and the effect of carbon monoxide (CO) on its gas separation performance

Industrial hydrogen production may prefer CO2-selective membranes because high-pressure H2 can therefore be produced without additional recompression. In this study, high performance CO2-selective membranes are fabricated by modifying a polymer–silica hybrid matrix (PSHM) with a low molecular weight poly(ethylene glycol) dimethyl ether (PEGDME). The liquid state of PEGDME and its unique end groups eliminate the crystallization tendency of poly(ethylene glycol) (PEG). The methyl end groups in PEGDME hinder hydrogen bonding between the polymer chains and significantly enhance the gas diffusivity. In pure gas tests, the membrane containing 50 wt% additive shows CO2 gas permeability and CO2/H2 selectivity of 1637Barrers and 13 at 35°C, respectively. In order to explore the effect of real industrial conditions, the gas separation performance of the newly developed membranes has been studied extensively using binary (CO2/H2) and ternary gas mixtures (CO2/H2/carbon monoxide (CO)). Compared to pure gas performance, the second component (H2) in the binary mixed gas test reduces the CO2 permeability. The presence of CO in the feed gas stream decreases both CO2 and H2 permeability as well as CO2/H2 selectivity as it reduces the concentration of CO2 molecules in the polymer matrix. The mixed gas results affirm the promising applications of the newly developed membranes for H2 purification.

Effect of Temperature on the Aqueous Two-Phase System Containing Poly(ethylene glycol) Dimethyl Ether 2000 and Dipotassium Oxalate

Liquid–liquid equilibria (LLE) of the poly(ethylene glycol) dimethyl ether 2000 (PEGDME2000) + dipotassium oxalate + H2O system have been determined experimentally at T = (298.15, 303.15, 308.15, a...

Super- and sub-Einstein intrinsic viscosities of spherical nanoparticles in concentrated low molecular weight polymer solutions

We explore the intrinsic viscosity of 40 nm silica particles in concentrated solutions of low molecular weight hydroxyl terminated polyethylene glycol (PEG), polyethylene glycol dimethyl ether (PEGDME) and polytetrahydrofuran (PTHF). Our goal is to develop a correlation between the intrinsic viscosity and the strength of the polymer segment-surface attractions, εpc. We show when the particles are large compared to the polymer radius of gyration and the polymer molecular weight is below the entanglement molecular weight, the intrinsic viscosity can be larger or smaller than the Einstein value of 2.5 expected for spheres with hard surfaces experiencing no-slip boundary conditions at the fluid/particle interface. Extensive small angle X-ray scattering studies are undertaken to extract εpc and establish the thermodynamic state of particle dispersion. We demonstrate a monotonic dependence of intrinsic viscosity on εpc with weaker polymer segment-particle surface interactions leading to sub-Einstein intrinsic viscosities. When interpreted in terms of a continuum model, our results suggest that the variations in intrinsic viscosity can be understood in terms of adsorbed layers which can have different viscosities from that of bulk fluid and which can slip at the particle surface. Increased layer viscosities are encouraged by large εpc while slip and or low viscosities are encouraged by low εpc.

(Liquid + liquid) equilibrium of the ternary aqueous system containing poly ethylene glycol dimethyl ether 2000 and tri-potassium citrate at different temperatures

(Liquid+liquid) equilibria (LLE) of the {poly ethylene glycol di-methyl ether 2000 (PEGDME2000)+tri-potassium citrate+H2O} system have been determined experimentally at T=(298.15, 303.15, 308.15, and 318.15)K. The effect of temperature on the binodals and tie-lines for the investigated aqueous two-phase system (ATPS) has also been studied. In this work, the three fitting parameters of the Merchuk equation and an empirical equation that we proposed in our previous work were obtained with the temperature dependence expressed in the linear form with (T−T0)K as a variable. Furthermore, the Othmer–Tobias and Bancroft, a temperature dependent Setschenow-type equation and osmotic virial model, the segment-based local composition models (the extended NRTL and the modified NRTL) were used for the correlation and prediction of the liquid–liquid phase behavior of the system studied. In addition, the effect of the polymers PEGDME2000 and poly ethylene glycol 2000 on the phase forming ability were studied. Also, the free energies of cloud points for this system were calculated from which it was concluded that the increase of the entropy is driving force for formation of studied aqueous two-phase system.