Novel polymer electrolytes prepared by copolymerization of ionic liquid monomers

Ionic liquid monomer couples were prepared by the neutralization of 1‐vinylimidazole with vinylsulfonic acid or 3‐sulfopropyl acrylate. These ionic liquid monomer couples were viscous liquid at room temperature and showed low glass transition temperature (Tg) at ?83 °C and ?73 °C, respectively. These monomer couples were copolymerized to prepare ion conductive polymer matrix. Thus prepared ionic liquid copolymers had no carrier ions, and they showed very low ionic conductivity of below 10^?9 S cm^?1. Equimolar amount of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) to imidazolium salt unit was then added to generate carrier ions in the ionic liquid copolymers. Poly(vinylimidazolium‐co‐vinylsulfonate) containing equimolar LiTFSI showed the ionic conductivity of 4 × 10^?8 S cm^?1 at 30 °C. Advanced copolymer, poly(vinylimidazolium‐co‐3‐sulfopropyl acrylate) which has flexible spacer between the anionic charge and polymer main chain, showed the ionic conductivity of about 10^?6 S cm^?1 at 30 °C, which is 100 times higher than that of copolymer without spacer. Even an excess amount of LiTFSI was added, the ionic conductivity of the copolymer kept this conductivity. This tendency is completely different from the typical polyether systems. Copyright © 2002 John Wiley & Sons, Ltd.     

High ionic conductivity of all-solid polymer electrolytes based on polyorganophosphazenes

A series of all-solid polymer electrolytes were prepared by cross-linking new designed poly(organophosphazene) macromonomers. The ionic conductivities of these all-solid, dimensional steady polymer electrolytes were reported. The temperature dependence of ionic conductivity of the all-solid polymer electrolytes suggested that the ionic transport is correlated with the segmental motion of the polymer. The relationship between lithium salts content and ionic conductivity was discussed and investigated by Infrared spectrum. Furthermore, the polarity of the host materials was thought to be a key to the ionic conductivity of polymer electrolyte. The all-solid polymer electrolytes based on these poly(organophosphazenes) showed ionic conductivity of 10⁻⁴ S cm⁻¹ at room temperature.     

Effect of MgO nanoparticles on ionic conductivity and electrochemical properties of nanocomposite polymer electrolyte

This paper analyzes the comparison between the performances and morphologies of the PMMA gel and composite electrolyte membrane with nanosized MgO particles. These polymer electrolytes were studied in detailed using XRD, DSC, SEM and AC impedance analysis. The conductivity enhancement has been attributed to the addition of ceramic filler that yields a significant increase of surface to volume ratio related to the decrease in glass transition temperature values in the composite polymer electrolyte. Good interfacial stability at the electrode/electrolyte interface resulted on account of the improved ion dissociation by ceramic filler and a rise in the room temperature conductivity (8.14 × 10⁻³ S cm⁻¹) due to the iono-covalent or Lewis acid–base bonds to the ions and ether oxygen base groups was also observed. Further enhancement of conductivity has been observed on MgO surface, as Lewis-acidic sites interact with both PMMA and ClO₄⁻ ions. The percentage of swelling was found to increase with increasing soaking periods upto 12 h. Beyond that soaking period, it was found that there was a negligible increase in the % of swelling.     

Depolymerization and ionic conductivity of enzymatically deproteinized natural rubber having epoxy group

Preparation of liquid epoxidized natural rubber (ENR) was made by oxidative depolymerization of ENR in latex stage without loss of epoxy group. Epoxidation of fresh natural rubber latex, which was purified by deproteinization with proteolytic enzyme and surfactant, was carried out with freshly prepared peracetic acid. The glass transition temperature (T_g) and gel content of the rubbers increased after the epoxidation, both of which were dependent upon an amount of peracetic acid. The gel content was significantly reduced by oxidative depolymerization of the rubber with (NH₄)₂S₂O₈ in the presence of propanal. The resulting liquid epoxidized rubber (M_n≈10⁴) was found to have well-defined terminal groups, i.e. aldehyde groups and α-β unsaturated carbonyl groups. The novel rubber was applied to transport Li⁺ as an ionic conducting medium, that is, solid polymer electrolyte.     

An analysis of ionic conductivity in polymer electrolytes

Conductivities for a wide variety of ionically conducting polymer electrolytes with a range of salt compositions have been investigated over the temperature region T_g to 370 K. When the conductivity data are analyzed as a function of temperature using the empirical Vogel-Tammann-Fulcher (VTF) equation a common trend is observed in that deviations in the fits to the data invariably occur in the temperature range 1.2 T_g to 1.4 T_g for all of the samples investigated. This deviation is interpreted as a decoupling of the ions from polymer segmental motion. Recent ²³Na NMR and ²²Na positron annihilation studies of sodium salt-based polymer electrolytes support this interpretation with evidence of a change in dynamics at about 1.2T_g. © 1994 John Wiley & Sons, Inc.     

Ionic liquids to the rescue? Overcoming the ionic conductivity limitations of polymer electrolytes

Polymer electrolytes – solid polymeric membranes with dissolved salts – are being intensively studied for use in all-solid-state lithium-metal-polymer (LMP) batteries to power consumer electronic devices. The low ionic conductivity at room temperature of existing polymer electrolytes, however, has seriously hindered the development of such batteries for many applications. The incorporation of salts molten at room temperature (room temperature ionic liquids or RTILs) into polymer electrolytes may be the necessary solution to overcoming the inherent ionic conductivity limitations of ‘dry’ polymer electrolytes.     

Liquid crystalline side chain polymer with a poly (Geraniol-co-MMA) backbone and phenylbenzoate mesogenic group: synthesis and characterization

A new side chain liquid crystalline polymers have been synthesized and characterized in which [geraniol-co-MMA] polymer are used as a backbone linked via polymethylene spacer to phenyl benzoate mesogenic group. The polymer exhibits enantiotropic liquid crystallinity with nematic phase and does not exhibit side chain crystallization .A clear difference between the nature of the mesophase is evidenced between [Geraniol-co-MMA] main chain and methacrylate polymers .The LC polymer exhibit glass transition at 40 °C. In a comparative analysis, we discuss the relevance of polymer backbone in the synthesis of side chain liquid crystalline polymers.     

Ionogels: Squeeze flow rheology and ionic conductivity of quasi-solidified nanostructured hybrid materials containing ionic liquids immobilized on halloysite

Ionogels are hybrid ion-conducting materials consisting of ionic liquids stabilized by inorganic or polymer fillers and having good prospects for application in solid-state and flexible electronics and energy storage devices. The work presents the results of studying the rheological properties and ionic conductivity of a series of ionogels based on halloysite nanoclay and bis(trifluoromethylsulfonyl)imide ionic liquids with EMIm⁺, BMIm⁺, BM₂Im⁺, BMPyrr⁺, BMPip⁺ and MOc₃Am⁺ cations and content of the dispersion phase of 43–48%. The obtained values are compared with the analogous characteristics of bulk ionic liquids. It has been established that the IL cation structural characteristics affect the viscoplastic properties of ionogels subjected to uniaxial quasistatic compression (20 °C), ionic conductivity and structural resistance coefficient of an inorganic filler (from ?20 to +80 °C). Additive models of conductivity in binary systems are applied to obtain correlations linking ionic conductivity of ionogels with that of pure ionic liquids.     

A novel composite polymer electrolyte containing room-temperature ionic liquids and heteropolyacids for dye-sensitized solar cells

A novel composite polymeric gel comprising room-temperature ionic liquids (1-butyl-3-methyl-imidazolium-hexafluorophosphate, BMImPF₆) and heteropolyacids (phosphotungstic acid, PWA) in poly(2-hydroxyethyl methacrylate) matrix was successfully prepared and employed as a quasi-solid state electrolyte in dye-sensitized solar cells (DSSCs). These composite polymer electrolytes offered specific benefits over the ionic liquids and heteropolyacids, which effectively enhanced the ionic conductivity of the composite polymer electrolyte. Unsealed devices employing the composite polymer electrolyte with the 3% content of PWA achieved the solar to electrical energy conversion efficiency of 1.68% under irradiation of 50 mW cm⁻² light intensity, increasing by a factor of more than three compared to a DSSC with the blank BMImPF₆-based polymer electrolyte without PWA. It is expected that these composite polymer electrolytes are an attractive alternative to previously reported hole transporting materials for the fabrication of the long-term stable quasi-solid state or solid state DSSCs.     

Quasi-solid-state dye-sensitized solar cell based on a polymer gel electrolyte with in situ synthesized ionic conductors

A polymer gel electrolyte with in situ synthesized Acac-Py-I₂ ionic conductors was prepared for fabricating a quasi-solid-state dye-sensitized solar cell (QS-DSSC). The in situ synthesized Acac-Py-I₂ ionic conductors show weaker influence on the liquid electrolyte absorbency of the polymer gel electrolyte than that of Acac-Py-I₂ ionic conductors dissolved in liquid electrolyte. Owing to the higher liquid electrolyte absorbency, the polymer gel electrolyte with in situ synthesized Acac-Py-I₂ ionic conductors shows higher ionic conductivity than that of polymer gel electrolyte with Acac-Py-I₂ ionic conductors absorbed from liquid electrolyte. QS-DSSC containing the polymer gel electrolyte with in situ synthesized Acac-Py-I₂ ionic conductors shows 3.815% energy conversion efficiency, which is 21.6% higher than that of QS-DSSC containing polymer gel electrolyte with Acac-Py-I₂ ionic conductors absorbed from liquid electrolyte.     

Mg-ion conducting gel polymer electrolyte membranes containing biodegradable chitosan: Preparation,structural, electrical and electrochemical properties

A biodegradable gel polymer electrolyte system based on chitosan/magnesium trifluoromethanesulfonate/1-ethyl-3-methylimidazolium trifluoromethanesulfonate (CA/Mg (Tf)₂/EMITf) is developed. The structure, thermal performance, mechanical properties, ionic conductivity, relaxation time, electrochemical stability and ionic transport number of the membranes are analyzed by various techniques. The ion migration mainly depends on the complexation and decomplexation of Mg²⁺ with amine band (NH₂) in chitosan. The 90CA-10Mg (Tf)₂ system plasticized with 10% EMITf (relative to the amount of 90CA-10Mg (Tf)₂) is identified as the optimum one and the temperature dependence of ionic conductivity obeys the Arrhenius rule. Moreover, the relaxation time of the electrolyte is very short, being just 1.25 × 10⁻⁶ s, and its electrochemical stability window is quite wide, being up to 4.15 V. The anodic oxidation and cathodic reduction of Mg at the Mg-electrode/electrolyte interface is facile, and the ionic transference number of this electrolyte is 0.985, indicating that it could be a potential electrolyte candidate for Mg-ion devices.     

Properties of a nanocomposite polymer electrolyte from an amorphous comb-branch polymer and nanoparticles

Three fully amorphous comb-branch polymers based on poly(styrene-co-maleic anhydride) as a backbone and poly(ethylene glycol) methyl ether of different molecular weights as side chains were synthesized. SiO₂ nanoparticles of various contents and the salt LiCF₃SO₃ were added to these comb-branch polymers to obtain nanocomposite polymer electrolytes. The thermal and transport properties of the samples have been characterized. The maximum conductivity of 2.8×10^–4 S cm^–1 is obtained at 28 °C. In the system the longer side chain of the comb-branch polymer electrolyte increases in ionic conductivity after the addition of nanoparticles. To account for the role of the ceramic fillers in the nanocomposite polymer electrolyte, a model based on a fully amorphous comb-branch polymer matrix in enhancing transport properties of Li⁺ ions is proposed.     

Structure and phase transitions of a liquid crystalline polymer

Summary The structures, textures as well as thermodynamic properties of a side chain polymer exhibiting a liquid crystalline phase in addition to a partially crystalline state and the isotropic fluid state were investigated. Furthermore the kinetics of phase transitions between these states were analyzed. It was found that the properties of this polymer are intermediate between that of low molecular weight liquid crystals and common polymers. In particular it was observed that the relation between the liquid crystalline texture and the structure is different from that of low molecular weight liquid crystals and that the properties of the crystalline and liquid crystalline state depend strongly on the tacticity of the polymer.

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Zusammenfassung Für ein Seitenkettenpolymeres, das zusätzlich zum teilkristallinen Zustand und zur isotropen Schmelze einen flüssig-kristallinen Zustand aufweist, wurden die Strukturen und Texturen untersucht sowie thermodynamische Eigenschaften. Außerdem wurde die Kinetik der Phasenumwandlungen analysiert. Es zeigt sich, daß die Eigenschaften zwischen denen üblicher Polymerer und denen von niedrigmolekularen flüssigen Kristallen liegen. Insbesondere zeigte sich, daß die Beziehung zwischen molekularer Struktur und Textur von der bei niedrigmolekularen flüssigen Kristallen abweicht, und daß die Taktizität der Kette einen starken Einfluß auf die Eigenschaften nicht nur der kristallinen Phase sondern auch der flüssig-kristallinen Phase ausübt.

     

Influence of PEG-borate ester on thermal property and ionic conductivity of the polymer electrolyte

We have focused on the poly(ethylene glycol) (PEG)-borate ester as a new type plasticizer for solid polymer electrolyte for lithium ion secondary battery. Adding the PEG-borate ester into the electrolyte shows the increase in the ionic conductivity of the polymer electrolyte. By measuring the glass-transition temperature of the polymer electrolytes with DSC, it is found that the increase in ionic conductivity of the polymer electrolyte is due to the increase in ionic mobility. By investigating the temperature dependence of the ionic conductivity of the polymer electrolytes using William-Landel-Ferry type equation, we considered that the PEG-borate ester does not have any influence for dissociation of Li-salt. This revised version was published online in August 2006 with corrections to the Cover Date.     

Enhanced ionic conductivity of poly(ethylene oxide) (PEO) electrolyte by adding mesoporous molecular sieve LiAlSBA

Mesoporous molecular sieve LiAlSBA was prepared via an ion exchange process with mesoporous AlSBA directly, which has a regular 2D hexagonal structure with pore size about 7 nm. It was added into poly(ethylene oxide) (PEO) solid electrolyte as filler. The characteristics of the composite polymer electrolyte were determined by XRD, DSC, TGA, FTIR, PLM and electrochemical methods. Compared with bare PEO electrolyte, the adding of dispersed LiAlSBA powder improved the ionic conductivity of PEO polymer electrolyte more than three orders. The reason for it is that mesoporous LiAlSBA powder acts as crystal cores in PEO composite electrolyte and fines the crystallites, decreases the crystallinity, which provides much more continuous amorphous domain for Li⁺ moving easily in PEO electrolyte. Besides, lithium ions of the mesoporous molecular sieves can hop from one site to another along the surface of the mesoporous channels, this mechanism is absent in the case of common nano-ceramic fillers in PEO electrolyte.     

Thermal and ionic conductivity studies of plasticized PMMA/PVdF blend polymer electrolytes

Poly(methylmethacrylate) (PMMA)/poly(vinylidene fluoride) (PVdF) blend based electrolyte films containing different lithium salt concentrations are prepared using solvent casting technique. The complexation has been confirmed using XRD and FTIR spectral studies. Ionic conductivity and thermal behaviour of PMMA/PVdF complexes were studied with various salt concentrations, temperature and plasticizer content. The network structure of the polymer complexes are also investigated using SEM. The maximum value of conductivity 4.2×10⁻³ S/cm is obtained for the PMMA(7.5)-PVdF(17.5)-LiClO₄(8)-DMP(67) polymer complex at 303 K.     

Gelation and ionic conductivity of fluoroalkyl end-capped 2-acrylamido-2-methylpropanesulfonic acid oligomers in ionic liquids

Fluoroalkyl end-capped 2-acrylamido-2-methylpropanesulfonic acid oligomer could cause a gelation in an ionic liquid (1-methylpyrazolium tetrafluoroborate) under non-crosslinked conditions. This new fluorinated oligomer gel formed in the ionic liquid was found to exhibit a high ionic (proton) conductivity of 10⁻² S/cm level at room temperature.     

Synthesis, characterization and properties of high molecular weight poly(butylenes succinate) reinforced by mesogenic units

To increase the molecular weights of the synthesized liquid crystalline aromatic/aliphatic copolyesters and to avoid crosslinking, a solution polymerization of the prepolymer and chain extender hexamethylene diisocyanate was adopted. The effects of chain extension on polyester molecular weights, thermal and mechanical properties, and biodegradable behaviors were investigated respectively. The catalysis mechanism and the copolyesters morphological textures were also investigated. The synthesized copolyesters were characterized by means of Fourier transform infrared spectra (FTIR), gel permeation chromatography (GPC), viscosity measurements, differential scanning calorimetry (DSC), X-ray diffraction (XRD), polarizing light microscopy (PLM), scanning electron microscopy (SEM) and mechanical property measurements. It was found that inherent viscosities and the molecular weights of the copolyesters were remarkably increased under the action of catalyst, leading to a increase in the tensile strength. The degree of relative crystallinity, the melting temperature, and the rate of degradation decreased after chain extension.     

On the ionic conductivity of polymer electrolytes in terms of hole fraction

A theoretical model to interpret the conductivity of ions through polymer electrolytes is established in terms of the temperature and pressure‐dependent hole fraction computed from Simha‐Somcynsky hole theory. The model successfully linearizes the logarithm of PPG and PEG conductivity data with NaCF₃SO₃ in a 20:1 ratio for a broad range of temperature and pressure. The conductivity parameter and transmission coefficient with an additive hole fraction constant are discussed and compared for both species. The derivative of the logarithm of conductivity with respect to the hole fraction decreases inversely with the hole fraction and saturates at about 0.08 and 0.12 hole fractions for PPG and PEG, respectively. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 2249–2254, 2008     

Structural,thermal, and impedance properties of a gel polymer electrolyte containing ionic liquid

The gel polymer electrolytes composed of ionic liquid, 1‐butyl‐3‐methylimidazolium tetrafluoroborate (BMImBF₄) and the copolymer of acrylonitrile (AN), methyl methacrylate (MMA), poly(ethylene glycol) methyl ether methacrylate (PEGMEMA) are synthesized and characterized by FT‐IR spectra, TGA, DSC, and AC impedance measurements. IR spectra show that there is an interaction between PEO side chains of the copolymer and imidazolium cations. TGA measurements indicate that the gel polymer electrolytes are stable until 120°C. By using the equivalent circuit proposed, the experimental data and the simulated data fit very well. The bulk resistance R_b is found to decrease with the increase in BMImBF₄ content. Copyright © 2009 John Wiley & Sons, Ltd.