AC complex impedance measurement of comb-like type polyether electrolytes under high-pressure carbon dioxide

The effect of high-pressure carbon dioxide on ionic conductivity for comb-like type polyether electrolytes based on oligo(oxyethylene glycol) methacrylate with lithium triflate, LiCF₃SO₃, has been investigated for the first time. Our investigations have focused on the correlation between the segmental motion of the polymer side chains and the efficiency of ion transport under supercritical carbon dioxide (scCO₂) conditions. Consequently, the ionic conductivity under the condition of 10 MPa and 40 °C CO₂ sample was more than 30 times elevated compared with the original one. The improvement of ionic conductivity is attributed to an increase in the polymer segmental motion via a decrease in activation volume and enhanced the number of charge carriers. The temperature dependence of log σ followed Vogel-Tamman-Fulcher (VTF) equation. However, the pressure dependence under scCO₂ condition was ascribed to the Arrhenius behavior resulting in an increase of the ionic conductivity with increasing the pressure.     

Synthesis of amphiphilic poly(phthalazinone ether sulfone ketone)‐graft‐poly(ethylene glycol) graft copolymers via Williamson etherification

Amphiphilic graft copolymers consisting of poly(phthalazinone ether sulfone ketone) (PPESK) backbones and poly(ethylene glycol) (PEG) side chains were synthesized via reaction of chloromethylated PPESK (CMPPESK) with a sodium alkoxide of methoxyl PEG (PEG‐ ONa). The reactive precursor, CMPPESK, was prepared by the chloromethylation of PPESK with chloromethylether (CME) using concentrated H₂SO₄ as reaction medium. FTIR spectroscopy, ¹H‐NMR and Solid‐state ¹³C CP‐MAS NMR analysis confirmed the covalent linking of PEG with PPESK backbones. The PEG content in the graft copolymers from ¹H‐NMR analysis varied from 21.0 to 37.2 wt %, which was approximately in agreement with that calculated from TGA tests. The graft products have good solubility in many aprotic polar solvents and can be slightly swelled by water and ethanol, but water insoluble. Contact angle measurements revealed that the hydrophilicity of PPESK was significantly improved by the introduction of PEG graft chains, indicating the graft copolymer is a potential hydrophilic additive for PPESK membranes. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007.     

Polymer gel electrolytes synthesized by photopolymerization in the presence of star-shaped oligo(ethylene glycol) ethers (OEGE)

The photoinitiated cross-linking polymerization of tri(ethylene glycol) dimethacrylate and its copolymerization with cyanomethyl methacrylate in the presence of LiCF₃SO₃ and of various oligo(ethylene glycol) methyl ethers as plasticizer was studied for potential use of the resulting polymer gel electrolytes in lithium batteries. Comparing linear and star-shaped (three and four arm molecules) oligo(ethylene glycol) methyl ethers, the influence of the architecture of the plasticizers on the polymerization course was investigated by means of differential scanning calorimetry. Linear and star-shaped plasticizers with molar masses < 1000 g/mol differ from each other concerning the dependence of their viscosity on their molar mass but not concerning the influence of the viscosity on the polymerization rate. Compared with linear plasticizers, the star-shaped ones have as an essential advantage a distinctly lower tendency to crystallize which is even completely suppressed in some cases. The gels were characterized with regard to the network density of their polymer matrix, to their thermal transitions, thermo-mechanical properties and ionic conductivity. The conductivity of solutions and gels with star-shaped plasticizers was slightly lower than that with linear ones at temperatures above room temperature.     

Comparison of micelles formed by amphiphilic poly(ethylene glycol)‐b‐poly(trimethylene carbonate) star block copolymers

In this article, we describe the synthesis and solution properties of PEG‐b‐PTMC star block copolymers via ring‐opening polymerization (ROP) of trimethylene carbonate (TMC) monomer initiated at the hydroxyl end group of the core PEG using HCl Et₂O as a monomer activator. The ROP of TMC was performed to synthesize PEG‐b‐PTMC star block copolymers with one, two, four, and eight arms. The PEG‐b‐PTMC star block copolymers with same ratio of between hydrophobic PTMC and hydrophilic PEG segments were obtained in quantitative yield and exhibited monomodal GPC curves. The amphiphilic PEG‐b‐PTMC star block copolymers formed spherical micelles with a core–shell structure in an aqueous phase. The mean hydrodynamic diameters of the micelles increased from 17 to 194 nm with increasing arm number. As arm number increased, the critical micelle concentration (CMC) of the PEG‐b‐PTMC star block copolymers increased from 3.1 × 10^?3 to 21.1 × 10^?3 mg/mL but the partition equilibrium constant, which is an indicator of the hydrophobicity of the micelles of the PEG‐b‐PTMC star block copolymers in aqueous media, decreased from 4.44 × 10⁴ to 1.34 × 10⁴. In conclusion, we confirmed that the PEG‐b‐PTMC star block copolymers form micelles and, hence, may be potential hydrophobic drug delivery vehicles. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Biodegradability of poly(ethylene terephthalate) copolymers with poly(ethylene glycol)s and poly(tetramethylene glycol)

Poly(ethylene terephthalate) copolymers were prepared by melt polycondensation of dimethyl terephthalate and excess ethylene glycol with 10–40mol% (in feed) of poly(ethylene glycol) (E) and poly(tetramethylene glycol) (B), with molecular weight (MW) of E and B 200–7500 and 1000, respectively. The reduced specific viscosity of copolymers increased with increasing MW and content of polyglycol comonomer. The temperature of melting (T_m), cold crystallization and glass transition (T_g) decreased with the copolymerization. T_m depression of copolymers suggested that the E series copolymers are the block type at higher content of the comonomer. T_g was decreased below room temperature by the copolymerization, which affected the crystallinity and the density of copolymer films. Water absorption increased with increasing content of comonomer, and the increase was much higher for E1000 series films than B1000 series films. The biodegradability was estimated by weight loss of copolymer films in buffer solution with and without a lipase at 37°C. The weight loss was enhanced a little by the presence of a lipase, and increased abruptly at higher comonomer content, which was correlated to the water absorption and the concentration of ester linkages between PET and PEG segments. The weight loss of B series films was much lower than that of E series films. The abrupt increase of the weight loss by alkaline hydrolysis is almost consistent with that by biodegradation.     

Synthesis and hydrophilicity of poly(butylene 2,6‐naphthalate)/poly(ethylene glycol) copolymers

Poly(butylene 2,6‐naphthalate) (PBN)/poly(ethylene glycol) (PEG) copolymers were synthesized by the two‐step melt copolymerization process of dimethyl‐2,6‐naphthalenedicarboxylate (2,6‐NDC) with 1,4‐butanediol (BD) and PEG. The copolymers produced had different PEG molecular weights and contents. The structures, thermal properties, and hydrophilicities of these copolymers were studied by ¹H NMR, DSC, TGA, and by contact angle and moisture content measurements. In particular, the intrinsic viscosities of PBN/PEG copolymers increased with increasing PEG molecular weights, but the melting temperatures (T_m)_, the cold crystallization temperatures (T_cc)_, and the heat of fusion (ΔH_f) values of PBN/PEG copolymers decreased on increasing PEG contents or molecular weights. The thermal stabilities of the copolymers were unaffected by PEG content or molecular weight. Hydrophilicities as determined by contact angle and moisture content measurements were found to be significantly increased on increasing PEG contents and molecular weights. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2677–2683, 2006     

Fabrication and properties of crosslinked poly(propylene carbonate maleate) gel polymer electrolyte for lithium‐ion battery

The poly(propylene carbonate maleate) (PPCMA) was synthesized by the terpolymerization of carbon dioxide, propylene oxide, and maleic anhydride. The PPCMA polymer can be readily crosslinked using dicumyl peroxide (DCP) as crosslinking agent and then actived by absorbing liquid electrolyte to fabricate a novel PPCMA gel polymer electrolyte for lithium‐ion battery. The thermal performance, electrolyte uptake, swelling ratio, ionic conductivity, and lithium ion transference number of the crosslinked PPCMA were then investigated. The results show that the T_g and the thermal stability increase, but the absorbing and swelling rates decrease with increasing DCP amount. The ionic conductivity of the PPCMA gel polymer electrolyte firstly increases and then decreases with increasing DCP ratio. The ionic conductivity of the PPCMA gel polymer electrolyte with 1.2 wt % of DCP reaches the maximum value of 8.43 × 10⁻³ S cm⁻¹ at room temperature and 1.42 × 10⁻² S cm⁻¹ at 50°C. The lithium ion transference number of PPCMA gel polymer electrolyte is 0.42. The charge/discharge tests of the Li/PPCMA GPE/LiNi_1/3Co_1/3Mn_1/3O₂ cell were evaluated at a current rate of 0.1C and in voltage range of 2.8–4.2 V at room temperature. The results show that the initial discharge capacity of Li/PPCMA GPE/LiNi_1/3Co_1/3Mn_1/3 O₂ cell is 115.3 mAh g⁻¹. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Gel electrolytes based on crosslinked tetraethylene glycol diacrylate/poly(ethylenimine) systems

Gel electrolytes were prepared by crosslinking low molecular weight poly(ethylenimine) (PEI) with tetraethylene glycol diacrylate (TEG) in the presence of 2-methoxyethyl ether (diglyme) and lithium triflate (LiTf). Impedance and infrared (IR) spectroscopies were used as complimentary tools for studying the mode of ion conduction in these gel electrolytes. Ionic conductivity measurements for all samples tested exhibited significant LiTf and diglyme composition dependency. The maximum ionic conductivity at 20 °C was 2×10⁻⁴ S/cm with moderate LiTf and high diglyme compositions. The calculated molal concentration of non-ionically bound ‘free’ triflate ion was found to vary directly with ionic conductivity with the highest molality ‘free’ triflate samples yielding the highest ionic conductivity. Lithium ion interactions with the triflate ion, diglyme and the crosslinked polymer matrix were observed with IR spectroscopy. A lower frequency shoulder on the v_s(CO) vibrational mode increases in intensity as LiTf composition is increased. Curve fitting and molar calculations suggest that over 85% of the total lithium ions available are coordinated to the TEG carbonyl at dilute LiTf compositions.     

Ionic conductivity studies of poly(ethylene oxide)-lithium salt electrolytes in high-pressure carbon dioxide

We have measured ionic conductivity of PEO-LiX [anion X=N(CF₃SO₂)₂ (TFSI), ClO₄, CF₃SO₃, BF₄, NO₃, and CH₃SO₃] polymer electrolytes in CO₂ at pressures varied from 0.1 to 20 MPa. From the temperature dependence in supercritical CO₂, a large increase in the conductivity for PEO-LiBF₄ and LiCF₃SO₃ electrolytes has been observed. Permeation of the CO₂ molecules gave rise to the plasticization for crystal domains in the electrolytes, which is related to the reduction in transition point of the Arrhenius plot corresponding to the melting of crystal PEO. Relation between the conductivity and CO₂ reduced density revealed that the electrolytes containing fluorinated anions such as ‘CO₂-philic’ BF₄ and CF₃SO₃ increase in the conductivity with increasing the density. This indicates that the salt dissociation was promoted by the CO₂ permeation and the Lewis acid-base interactions between fluorinated anions and CO₂ molecules.     

Physical and electrochemical properties of low molecular weight poly(ethylene glycol)‐bridged polysilsesquioxane organic–inorganic composite electrolytes via sol–gel process

A new class of ionic conducting organic/inorganic hybrid composite electrolyte with high conductivity, better electrochemical stability and mechanical behavior was prepared through the sol–gel processing between ethylene‐bridged polysilsesquioxane and poly(ethylene glycol) (PEG). The composite electrolyte with 0.05 LiClO₄ per PEG repeat unit has the best conductivity up to 10^?4 S/cm at room temperature with the transference number up to 0.48 and an electrochemical stability window as high as 5.5 V versus Li/Li⁺. Moreover, the effect of the PEG chain length on the properties of the composite electrolyte has also been studied. The interactions between ions and polymer have also been investigated for the composite electrolyte in the presence of LiClO₄ by means of FTIR, DSC, and TGA. The results indicated the interaction of Li⁺ ions with the ether oxygen of the PEG, and the formation of transient crosslinking with LiClO₄, resulting in an increase of the T_g of the composite electrolyte. The VTF‐type behavior of the ionic conductivity implied that the diffusion of the charge carriers was assisted by the segmental motions of the polymer chains. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2752–2758, 2007     

Effect of poly(ethylene glycol) on the solid‐state polymerization of poly(ethylene terephthalate)

Poly(ethylene glycol) (PEG) and end‐capped poly(ethylene glycol) (poly(ethylene glycol) dimethyl ether (PEGDME)) of number average molecular weight 1000 g mol^?1 was melt blended with poly(ethylene terephthalate) (PET) oligomer. NMR, DSC and WAXS techniques characterized the structure and morphology of the blends. Both these samples show reduction in T_g and similar crystallization behavior. Solid‐state polymerization (SSP) was performed on these blend samples using Sb₂O₃ as catalyst under reduced pressure at temperatures below the melting point of the samples. Inherent viscosity data indicate that for the blend sample with PEG there is enhancement of SSP rate, while for the sample with PEGDME the SSP rate is suppressed. NMR data showed that PEG is incorporated into the PET chain, while PEGDME does not react with PET. Copyright © 2005 Society of Chemical Industry     

The salting-out effect and phase separation in aqueous solutions of electrolytes and poly(ethylene glycol)

The compositions of coexisting phases have been determined for aqueous two-phase systems containing poly(ethylene glycol) (PEG) of nominal molecular weight 8000 and a series of eight electrolytes: NaOH, Na₂CO₃, Na₂SO₄, Na₂HPO₄, Na₃PO₄, (NH₄)₂SO₄, MgSO₄, ZnSO₄. The salting-out effects of the electrolytes on the polymer were obtained by fitting a Setschenow-type equation to the tie line data to derive a salting-out coefficient for each electrolyte. For the sodium salts the relative effectiveness of the anions in forming biphasic mixtures follows the Hofmeister series. The relative salting-out effectiveness of the sulphate salts, however, is probably influenced by complexation of the cations by PEG. The values of the salting-out coefficients reflect the extent of preferential hydration of the ethylene oxide units in the polymer chains.     

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 (BPh₃) additive on conductivity and lithium cation transference numbers in poly(ethylene oxide) dimethyl ether (PEODME)-lithium trifluoromethanesulfonate (LiCF₃SO₃, 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-LiCF₃SO₃ electrolyte. This effect is assisted by ionic conductivity enhancement.     

ABA triblock copolymers from poly(p‐dioxanone) and poly(ethylene glycol)

Poly(p‐dioxanone)–poly(ethylene glycol)–poly(p‐dioxanone) ABA triblock copolymers (PEDO) were synthesized by ring‐opening polymerization from p‐dioxanone using poly(ethylene glycol) (PEG) with different molecular weights as macroinitiators in N₂ atmosphere. The copolymer was characterized by ¹H NMR spectroscope. The thermal behavior, crystallization, and thermal stability of these copolymers were investigated by differential scanning calorimetry and thermogravimetric measurements. The water absorption of these copolymers was also measured. The results indicated that the content and length of PEG chain have a greater effect on the properties of copolymers. This kind of biodegradable copolymer will find a potential application in biomedical materials. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102:1092–1097, 2006     

An investigation of lithium ion conductivity of copolymers based on P(AMPS-co-PEGMA)

In this work, a series of novel lithium ion-conducting copolymer electrolytes based on 2-acrylamido-2-methyl-1-propane sulfonic acid (AMPS) and poly(ethyleneglycol) methacrylate (PEGMA) were produced and characterized. The copolymers were synthesized by free-radical polymerization of the corresponding monomers with three different feed ratios to form P(AMPS-co-PEGMA)-based electrolytes. After the polymerization, AMPS units of the copolymers were lithiated via ion exchange. The characterization of the electrolytes was done by ¹H-NMR, FTIR, differential scanning calorimetry (DSC), thermogravimetric analysis, X-ray diffraction, scanning electron microscopy (SEM), and impedance analyzer. The copolymers were thermal stable approximately to 200 °C. Single T_g transitions in DSC curves verified the homogeneity as well as amorphous characteristics. SEM further confirmed the homogeneity of the electrolytes. The lithium ion conductivity of these new polymer electrolytes was studied by impedance dielectric impedance analyzer and the effect of PEGMA contents onto the ionic conductivity of these copolymer electrolytes were investigated. It was observed that the temperature dependence of ionic conductivity was interpreted over Vogel Tammann Fulcher model. The Li ion conductivity increased by PEGMA content and S3 has maximum conductivity of 3 × 10⁻³ mS cm⁻¹ at 100 °C. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47798.     

Novel microporous poly(vinylidene fluoride)‐graft‐poly(tert‐butyl acrylate) electrolytes for secondary lithium batteries

BACKGROUND: Much interest has recently been shown in improving the performance of lithium‐ion polymer batteries with gel polymer electrolytes (GPEs) due to a rapid expansion in industrial demand. Novel GPEs based on poly(vinylidene fluoride)‐graft‐poly(tert‐butyl acrylate) (PVDF‐g‐tBA) microporous mats are suggested in this study. RESULTS: Microfibrous polymer electrolytes were prepared using electrospinning and characterized for extent of grafting, morphology, crystallinity, electrochemical stability, ionic conductivity, interfacial resistance and cell cycleability. The degree of crystallinity was lower for tBA‐grafted PVDF mats than that of neat PVDF. The PVDF‐g‐tBA showed an improvement in the ionic conductivity, electrochemical stability, interfacial resistance and cyclic performance. CONCLUSION: The tBA‐grafted PVDF microporous electrolytes are promising candidates for enhancing the performance of lithium‐ion polymer batteries. Copyright © 2008 Society of Chemical Industry     

Enhanced ion conductivity of poly(ethylene oxide)-based single ion conductors with lithium 1,2,3-triazolate end groups

Poly(ethylene oxide) (PEO)-based single ion conductors (SICs) are of great interest for applications in modern lithium ion batteries. They have several advantages over other common electrolytes such as high cation transference numbers, low toxicity, and nonflammability, but their major disadvantage is the low ion conductivity. Here, linear PEO-based SICs with lithium 1,2,3-triazolate (TrLi) end groups are synthesized and studied in terms of crystallinity by differential scanning calorimetry, and with respect to ion conductivity by impedance spectroscopy. Introduction of TrLi end groups to PEO chains reduces its crystallinity and melting temperature as well as an enhancement of the ion conductivity up to 8.0·10⁻⁶ S cm⁻¹ at 70°C is observed. The increased ion conductivity is a direct result of the Tr rings, which can actively contribute to the conduction mechanism. In comparison with conductivities of other PEO-based SICs reached so far (σ₀ ≤ 10⁻⁶ S cm⁻¹), the results of this study show that the introduction of TrLi end groups is a new approach to enhance the Li⁺-ion conductivity of PEO-based SICs that have also a good electrochemical stability versus lithium electrodes as revealed by linear sweep voltammetry. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 46949.     

A redox poly(ionic liquid) hydrogel: Facile method of synthesis and electrochemical sensing

In this article, a redox-responsive poly(ionic liquid) (redox-PIL) hydrogel Poly(1-vinyl-3-propionate imidazole phenothiazine sulfonic acid)-chitosan [Poly(VPI⁺PTZ-(CH₂)₃SO₃⁻)-CS] was produced by using chitosan (CS) crosslinking with redox-PIL Poly(1-vinyl-3-propionate imidazole phenothiazine sulfonic acid [Poly(VPI⁺PTZ-(CH₂)₃SO₃⁻)]. The incorporation of redox-active counter anions 3-(phenothiazine-10-yl) propane 1-sulfonic acid anions (PTZ-(CH₂)₃SO₃⁻) into cationic PIL-polyimidazole rendered Poly(VPI⁺PTZ-(CH₂)₃SO₃⁻) with electron catalytic ability, ionic conductivity, and electron conductivity. Poly(VPI⁺PTZ-(CH₂)₃SO₃⁻)-CS combines the properties of hydrogel and redox-PIL, thus offering intrinsic porous conducting frameworks and promoting the transport of charges, ions, and molecules, leading hydrogel with excellent electrochemical properties. The crosslinking occurrence of Poly(VPI⁺PTZ-(CH₂)₃SO₃⁻) and CS resulting from the synthetic process of hydrogel was verified by differential scanning calorimetry and thermogravimetric analysis. A three-dimensional polymer network hydrogel with good biocompatibility and permeability was formed after crosslinking. In addition, only 64% weight loss within 600 °C was observed in Poly(VPI⁺PTZ-(CH₂)₃SO₃⁻)-CS representing its thermally stable performance. When used as an electrochemical sensor, the hydrogel-modified gold electrode improved the electrocatalytic oxidation of cysteine. Differential pulse voltammetry results indicated that the detection range was from 5 × 10⁻⁸ to 5 × 10⁻³ M and the limit of detection was 6.64 × 10⁻⁸ M. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48051.     

Modification of zein films by incorporation of poly(ethylene glycol)s

The thermal and mechanical properties of corn (maize) (CZ) films plasticized with poly(ethylene glycol) (PEG) of two different molar masses (400 and 1000 g mol⁻¹) were studied using differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA), tensile strength, moisture absorption isotherms and water vapour transmission rate measurements. The glass transition temperature (T_g) of plasticized films is determined primarily by the amount of moisture contained in the film. DMTA data show contraction of films with loss of absorbed water during heating/cooling cycles. The moisture absorption behaviour of films plasticized with PEG400 and PEG1000 is similar at low relative humidities but significantly different at higher relative humidities. Incorporation of up to about 30 wt% PEG substantially enhances the tensile strength and the resistance to water vapour transmission of the protein film, and PEG1000 is more effective than PEG400. © 2000 Society of Chemical Industry     

The effect of different lithium salts on conductivity of comb-like polymer electrolyte with chelating functional group

The behaviors of lithium ions in a comb-like polymer electrolyte with chelating functional group complexed with LiCF₃SO₃, LiBr and LiClO₄ were characterized by differential scanning calorimeter (DSC), thermogravimetric analysis (TGA), Fourier transform infrared (FT-IR) spectroscopy, AC impedance, and ¹³C solid-state NMR measurement. The comb-like copolymer was synthesized from poly(ethylene glycol) methyl ether methacrylate (PEGMEM) and (2-methylacrylic acid 3-(bis-carboxymethylamino)-2-hydroxy-propyl ester) (GMA-IDA). FT-IR spectra reveal the interactions of Li⁺ ions with both the ether oxygen of the PEGMEM and the nitrogen atom of the GMA-IDA segments. FT-IR spectra also indicate an increasing anion-cation association consistent with increasing LiCF₃SO₃ concentrations. Moreover, the ¹³C solid-state NMR spectra for the carbons attached to the ether oxygen atoms exhibited significant line broadening and a slight upfield chemical shift when the dopant was added to the polymer. These findings indicate coordination between the Li cation and the ether oxygens in the PEG segment. T_g and T_d of copolymers doped with salts clearly increase, as shown by DSC and TGA measurements. These results indicate the interactions of Li⁺ with both PEGMEM and GMA-IDA segments form transient cross-links inside the copolymers. The Vogel-Tamman-Fulcher (VTF)-like behavior of conductivity implies the coupling of the charge carriers with the segmental motion of the polymer chain in this study. The maximum conductivity of copolymers relates to the composition of the copolymers and the concentration of doping lithium ions. In summary, the GMA-IDA unit in the copolymer promotes the dissociation of the lithium salt, the mechanical strength and the conductivity of the polyelectrolyte.