Soft segmental effect of methylene bis(p‐cyclohexyl isocyanate) based thermoplastic polyurethane impregnated with lithium perchlorate/propylene carbonate on ionic conductivity

Thermoplastic polyurethane (TPU) was employed as the polymer matrix for ion conduction as gelled electrolytes with lithium perchlorate (LiClO₄) in propylene carbonate (PC) solution. The TPU was prepared by methylene bis(p‐cyclohexyl isocyanate) as the hard segment while employing both poly(ethylene glycol) (PEG) and poly(tetramethylene glycol) (PTMG) as the soft segments. The copolymer comprising both PEG and PTMG was prepared such that it possessed the combined characteristics of good conductivity from the former and good mechanical properties from the latter. All the polymers were characterized by gel permeation chromatography, differential scanning calorimetry, and Fourier transform IR spectroscopy. The conductivity data were obtained from alternating current impedance experiments. The results revealed that the copolymer containing both PEG and PTMG as the soft segments showed better performance than TPU containing either PEG or PTMG. The copolymer TPU(PEG/PTMG) proved to be a good gelled electrolyte from 5 to 85°C. This copolymer, impregnated with 150% LiClO₄/PC, possessed good mechanical strength and conductivity as high as 10^?3 S/cm. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 935–942, 2001     

Blending poly(methyl methacrylate) and poly(styrene‐co‐acrylonitrile) as composite polymer electrolyte

A blend of poly(methyl methacrylate) (PMMA) and poly(styrene‐co‐acrylonitrile) (PSAN) has been evaluated as a composite polymer electrolyte by means of differential scanning calorimetry (DSC), Fourier transform infrared (FTIR) spectroscopy, ac impedance measurements, and linear sweep voltammetry (LSV). The blends show an interaction with the Li⁺ ions when complexed with lithium perchlorate (LiClO₄), which results in an increase in the glass‐transition temperature (T_g) of the blends. The purpose of using PSAN as another component of the blend is to improve the poor mechanical properties of PMMA‐based plasticized electrolytes. The mechanical property is further improved by introducing fumed silica as inert filler, and hence the liquid electrolyte uptake and ionic conductivity of the composite systems are increased. Room‐temperature conductivity of the order of 10^?4 S/cm has been achieved for one of the composite electrolytes made from a 1/1 blend of PSAN and PMMA containing 120% liquid electrolyte [1M LiClO₄/propylene carbonate (PC)] and 10% fumed silica. These systems also showed good compatibility with Li electrodes and sufficient electrochemical stability for safe operation in Li batteries. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1319–1328, 2001     

Thermal, electrical and mechanical properties of plasticized polymer electrolytes based on PEO/P(VDF-HFP) blends

The polymer electrolytes composed of a blend of poly(ethylene oxide) (PEO) and poly(vinylidene fluoride-co-hexafluoropropylene) (P(VDF-HFP)) as a host polymer, mixture of ethylene carbonate (EC) and propylene carbonate (PC) as a plasticizer, and LiClO₄ as a salt were prepared by a solution casting technique. SEM micrographs show that P(VDF-HFP) is very compatible with PEO. The ionic conductivity of the electrolytes increases with increasing plasticizer content, while the mechanical properties become obviously worse. By addition of a certain content of PEO in P(VDF-HFP) matrix, a good compromise between high ionic conductivity and mechanical stability can be obtained.     

Effect of different plasticizer on structural and electrical properties of PEMA-based polymer electrolytes

Plasticized poly(vinyl chloride)/poly(ethyl methacrylate) PVC/PEMA-based blend polymer electrolyte films containing lithium perchlorate (LiClO₄) as a salt were prepared by solvent casting technique. The effects of the plasticization on structural, thermal and electrical properties of the plasticized polymer blend electrolytes were investigated. The changes in the structural and complex formation properties of the materials were studied by XRD and FTIR techniques. Dielectric relaxation studies of the polymer electrolyte have been undertaken, and the results are discussed. TG/DTA technique is used to study the thermal stability. Complex impedance analysis is used to calculate the bulk resistance of the complexes. The effect of different plasticizer on the structural and physical properties of polymer blend electrolyte is well correlated.     

A study on polyurethane/acrylate crosslinked gel polymer electrolytes

2,4‐Toluene diisocyanate, poly(propylene glycol), poly(ethylene glycol) (PEG) and 2‐hydroxyethyl methacrylate were used to synthesize PEG–UA (urethane acrylate) monomer. The crosslinked polymer and gel polymer electrolytes were prepared in dioxane by free radical polymerization. The swelling behaviour, thermal degradation properties, morphology and ionic conductivity of the gel polymer electrolytes were investigated. With decrease in the proportion of dioxane used, the synthesized polymer's network density increased, its affinity with a solution of 1 M LiClO₄ in propylene carbonate (PC) decreased, and more microgel which diffused in the network. At the same time, the conductivity increased and reached 4 × 10^?4 S cm^?1 at 25 °C. Copyright © 2003 Society of Chemical Industry     

Influence of LiClO4 on the thermal,mechanical, and morphological properties of P(DMS‐co‐EO)/ P(EPI‐co‐EO) blends

The UV‐vis absorption, thermal analysis, ionic conductivity, mechanical properties, and morphology of a blend of poly(dimethylsiloxane‐co‐ethylene oxide) [P(DMS‐co‐EO)] and poly(epichlorohydrin‐co‐ethylene oxide) [P(EPI‐co‐EO)] (P(DMS‐co‐EO)/P(EPI‐co‐EO) ratio of 15/85 wt %) with different concentrations of LiClO₄ were studied. The maximum ionic conductivity (σ = 1.2 × 10^?4 S cm^?1) for the blend was obtained in the presence of 6% wt LiClO₄. The crystalline phase of the blend disappeared with increasing salt concentration, whereas the glass transition temperature (T_g) progressively increased. UV‐vis absorption spectra for the blends with LiClO₄ showed a transparent polymer electrolyte in the visible region. The addition of lithium salt decreased the tensile strength and elongation at break and increased Young's modulus of the blends. Scanning electron microscopy showed separation of the phases between P(DMS‐co‐EO) and P(EPI‐co‐EO), and the presence of LiClO₄ made the blends more susceptible to cracking. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1230–1235, 2004     

Morphological,infrared, and ionic conductivity studies of poly(ethylene oxide)–49% poly(methyl methacrylate) grafted natural rubber–lithium perchlorate salt based solid polymer electrolytes

The potential of poly(ethylene oxide) (PEO) and 49% poly(methyl methacrylate) grafted natural rubber (MG49) as a polymer host in solid polymer electrolytes (SPE) was explored for electrochemical applications. PEO–MG49 SPEs with various weight percentages of lithium perchlorate salt (LiClO₄) was prepared with the solution casting technique. Characterization by scanning electron microscopy, Fourier transform infrared spectroscopy, and impedance spectroscopy was done to investigate the effect of LiClO₄ on the morphological properties, chemical interaction, and ionic conductivity behavior of PEO–MG49. Scanning electron microscopy analysis showed that the surface morphology of the sample underwent a change from rough to smooth with the addition of lithium salts. Infrared analysis showed that the interaction occurred in the polymer host between the oxygen atom from the ether group (C? O? C) and the Li⁺ cation from doping salts. The ionic conductivity value increased with the addition of salts because of the increase in charge carrier up to the optimum value. The highest ionic conductivity obtained was 8.0 × 10^?6 S/cm at 15 wt % LiClO₄. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Solid polymer electrolytes. VII. Preparation and ionic conductivity of gelled polymer electrolytes based on poly(ethylene glycol) diglycidyl ether cured with α,ω‐diamino poly(propylene oxide)

Crosslinked polymer electrolyte networks were prepared from poly(ethylene glycol) diglycidyl ether blended with an epoxy resin (diglycidyl ether of bisphenol A) in different ratios and then cured with α,ω‐diamino poly(propylene oxide) in the presence of lithium perchlorate (LiClO₄) as a lithium salt. The ionic conductivities of these polymer electrolytes were determined by alternating current (AC) impedance spectroscopy. Propylene carbonate (PC) was used as a plasticizer to form gelled polymer electrolyte networks. The conductivities of the polymer electrolytes containing 46 wt % PC plasticizer were approximately 5 × 10^?4 S cm^?1 at 25°C and approximately 10^?3 S cm^?1 at 85°C. These polymer electrolytes were homogeneous and exhibited good mechanical properties. The effects of the polymer composition, plasticizer content, salt concentration, and temperature on the ionic conductivities of the polymer electrolytes were examined. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1264–1270, 2004     

Polymer gel electrolytes prepared by thermal curing of poly(vinylidene fluoride)-hexafluoropropene/poly(ethylene glycol)/propylene carbonate/lithium perchlorate blends

In an effort to prepare a poly(vinylidene fluoride)-hexafluoropropene (PVdF-HFP) based polymer gel film electrolyte with higher mechanical strength and little volatility, a two component urethane system employing blocked multiisocyanate as a potential thermal crosslinking agent, and low molar mass poly(ethylene glycol) (PEG) as a hydroxy-functional coreactant was blended with the PVdF-HFP gel system, and the cure of the blends was examined as a function of temperature, molar mass of PEG, and PEG/blocked isocyanate ratio. The network forming reaction could not proceed below 100 °C, but it slowly took place above 120 °C by thermal deblocking of blocked multiisocyanate, followed by the reaction of regenerated free multiisocyanate with PEG in the absence and presence of PVdF-HFP, plasticizer (propylene carbonate, PC) and lithium perchlorate. The adduct of polymeric methylene diphenyl diisocyante (PMDI) with acetone oxime was used as a potential thermal crosslinking agent for this study. Network polymer gels having no PVdF-HFP were also prepared for comparison. The cured (PVdF-HFP/PEG/blocked PMDI/PC/LiClO₄) polymer gel networks were mechanically and dimensionally stable, and their thermal characteristics and electrochemical properties were investigated using FT-IR spectroscopy, differential scanning calorimetry, electrochemical impedance spectroscopy and linear sweep voltammetry.     

Influence of Barium Titanate on poly(vinyl pyrrolidone)‐based composite polymer blend electrolytes for lithium battery applications

Nanocomposite polymer blend electrolytes based on poly (ethylene oxide), poly (vinyl pyrrolidone) that contained lithium perchlorate as a dopant, propylene carbonate (PC) as a plasticizer and Barium Titanate (BaTiO₃) as a filler were prepared for various concentrations of BaTiO₃ using solvent casting technique. The structural and complex formations of the composite electrolyte membranes were confirmed by X‐ray diffraction and FTIR analysis. The addition of BaTiO₃ nanofillers improved the ionic conductivity of the polymer electrolytes to some extent when the content of the BaTiO₃ is 10 wt%. The addition of BaTiO₃ also enhanced the thermal stability of the electrolyte. The surface morphology of the sample having a maximum ionic conductivity was studied by AFM. Molecular motion in the polymeric media was supported by fluorescence studies. The charge transfer arises between the polymer blend and Li‐ions were confirmed by UV‐Vis analysis. POLYM. COMPOS., 36:302–311, 2015. © 2014 Society of Plastics Engineers     

Structural characterization of hydrophilic polymer blends/montmorillonite clay nanocomposites

The nanocomposite films comprising polymer blends of poly(vinyl alcohol) (PVA), poly(vinyl pyrrolidone) (PVP), poly(ethylene oxide) (PEO), and poly(ethylene glycol) (PEG) with montmorillonite (MMT) clay as nanofiller were prepared by aqueous solution casting method. The X‐ray diffraction studies of the PVA–x wt % MMT, (PVA–PVP)–x wt % MMT, (PVA–PEO)–x wt % MMT and (PVA–PEG)–x wt % MMT nanocomposites containing MMT concentrations x = 1, 2, 3, 5 and 10 wt % of the polymer weight were carried out in the angular range (2θ) of 3.8–30°. The values of MMT basal spacing d₀₀₁, expansion of clay gallery width W_cg, d‐spacing of polymer spherulite, crystallite size L and diffraction peak intensity I were determined for these nanocomposites. The values of structural parameters reveal that the linear chain PEO and PEG in the PVA blend based nanocomposites promote the amount of MMT intercalated structures, and these structures are found relatively higher for the (PVA–PEO)–x wt % MMT nanocomposites. It is observed that the presence of bulky ester‐side group in PVP backbone restricts its intercalation, whereas the adsorption behavior of PVP on the MMT nanosheets mainly results the MMT exfoliated structures in the (PVA–PVP)–x wt % MMT nanocomposites. The crystallinities of the PEO and PEG were found low due to their blending with PVA, which further decreased anomalously with the increase of MMT concentration in the nanocomposites. The decrease of polymer crystalline phase of these materials confirmed their suitability in preparation of novel solid polymer nanocomposite electrolytes. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40617.     

Polymer electrolytes based on a ternary miscible blend of poly(ethylene oxide), poly(bisphenol A-co-epichlorohydrin) and poly(vinyl ethyl ether)

Ternary blends of poly(ethylene oxide) (PEO), poly(bisphenol A-co-epichlorohydrin) (PBE) and poly(vinyl ethyl ether) (PVEE) were obtained as films and characterized by differential scanning calorimetry (DSC) and vibrational spectroscopy (FTIR). From the DSC results, phase diagrams for the ternary blends were determined, where the variation of the viscoelastic phase extent as a function of the polymers composition was determined. The DSC results also indicated miscibility of the system, exhibiting only one glass transition temperature (T_g) and decrease in the crystallinity of the system, as well as decrease in the crystallinity of PEO present in the blends. Vibrational spectroscopy (FTIR) provided information on the intermolecular interactions between the pairs PBE/PEO and PBE/PVEE, via hydrogen bond interaction. From the FTIR analyses, molecular model systems of equilibrium among the interacting structures were proposed as a molecular basis for the miscibility of the system.Polymer electrolytes based on the ternary blend containing 60/25/15 (PEO/PBE/PVEE) mass percent and lithium perchlorate (LiClO₄) were obtained and characterized by DSC, FTIR, optical microscopy and electrochemical impedance spectroscopy (EIS). Solid electrolytes containing up to 10 wt% LiClO₄ exhibited a single-phase behavior, evidenced by the DSC results. For these electrolytes, FTIR spectra indicated the formation of polymer-ion complexes, in which the cation (Li⁺) acts favoring the polymer-polymer miscibility. Electrolytes containing LiClO₄ higher than 10 wt% exhibit a multiple phase behavior, in which a PEO-rich, salt-containing phase is present in equilibrium with PBE or PVEE-rich phases. Maximum ionic conductivity at room temperature, for the electrolyte containing 20 wt% LiClO₄, reached 4.23 × 10⁻³ Ω⁻¹ cm⁻¹, while all samples exhibited conductivity of approximately 10⁻¹ Ω⁻¹ cm⁻¹ at 80 °C.     

Antistatic performance and morphological observation of ternary blends of poly(ethylene terephthalate), poly(ether esteramide), and ionomers

Blends of poly(ethylene terephthalate) (PET) and poly (ether esteramide) (PEEA), which is known as an ion conductive polymer, were prepared by melt mixing using a twin screw extruder. Antistatic performance of the molded plaques and the effects of adding ionomers such as lithium neutralized poly(ethylene‐co‐methacrylic acid) copolymer(E/MAA‐Li), magnesium neutralized poly(ethylene‐co‐methacrylic acid) copolymer(E/MAA‐Mg), and zinc neutralized poly(ethylene‐co‐methacrylic acid) copolymer (E/MAA‐Zn) were investigated. Antistatic effect of adding poly(ethylene‐co‐methacrylic acid) copolymer(E/MAA) and polystyrene, and poly(ethylene naphthalate) (PEN) into PET/PEEA blends were also investigated. Here we confirmed that lithium ionomer worked the most effectively in those blend systems. We also confirmed that E/MAA worked to enhance the antistatic performance of PET/PEEA blends. Morphological study of these ternary blends system was conducted by TEM. Specific interaction between PEEA and E/MAA‐Li, and E/MAA were observed. Those ionomers and copolymer domains were encapsulated by PEEA, which could increase the surface area of PEEA in PET matrix. This encapsulation effect explains the unexpected synergy for the static dissipation performance on addition of ionomers and E/MAA to PET/PEEA blends. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers     

Review on composite polymer electrolytes for lithium batteries

This paper reviews the state of the art of composite polymer electrolytes (CPE) in view of their electrochemical and physical properties for the applications in lithium batteries. This review mainly encompasses on composite polymer electrolyte hosts namely poly(ethylene oxide) (PEO), poly(acrylonitrile) (PAN), poly(methyl methacrylate) (PMMA) and poly(vinylidene fluoride) (PVdF) studied so far. Also the ionic conductivity, transference number, compatibility and the cycling behavior of poly(vinylidene fluoride-hexafluoro propylene) (PVdF-HFP)-[AlO(OH)]_n-LiPF₆/LiClO₄ composite electrolytes have been studied and the results are discussed.     

Optimization of PVC– PAN‐based polymer electrolytes

The hybrid plasticized polymer electrolyte composed of the blend of poly(vinyl chloride) (PVC) and poly(acrylonitrile) (PAN) as host polymer, propylene carbonate as plasticizer, and LiClO₄ as a salt was studied. An attempt was made to optimize the polymer blend ratio. XRD, Fourier transform infrared, and DSC studies confirm the formation of polymer–salt complex and miscibility of the PVC and PAN. The electrical conductivity and temperature dependence of ionic conductivity of polymer films are also studied and reported here. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Thermal degradation of water soluble polymers and their binary blends

The effect of five different metal oxides on the pyrolysis of poly(ethylene oxide) (PEO), polyacrylamide (PAM), and poly(vinyl alcohol) (PVA) was investigated using thermogravimetry. The presence of metal oxide did not influence the degradation of PEO while the order of metal oxide on the degradation rate of PAM and PVA was PbO > Co₃O₄ > CuO > ZnO > Al₂O₃. The miscibility and the decomposition of PEO–PAM and PVA–PAM blends were also investigated. The blends were found to be immiscible and the presence of one polymer did not influence the degradation of the other polymer in the polymer blend. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 233–240, 2006     

New solid polymer electrolytes based on PEO/PAN hybrids

Hybrid polymer dry electrolytes comprised of poly(ethylene oxide) (PEO), polyacrylonitrile (PAN), and LiClO₄ were investigated. The impedance spectroscopy showed that the effect of PAN on the ion conductivity of PEO‐based electrolytes depends on the concentration of lithium salt. When the mole ratio of lithium to oxygen is 0.062 (15%LiClO₄‐PEO), adding PAN will increase the ionic conductivity. Differential scanning calorimetry, NMR, and IR data suggested that the enhanced conductivity was due to both the decreasing of the PEO crystallinity and increasing of the degree of ionization of lithium salt. There was obviously no interaction between PAN and lithium ions, and PAN acts as a reinforcing filler, and hence contributes to the mechanical strength besides reducing the crystallinity of the polymer electrolytes. When the LiClO₄‐PEO‐PAN hybrid polymer electrolyte was heated at 200°C under N₂, PAN crosslinked partially, which further decreased the crystallinity of PEO and increased the ionic conductivity, and at the same time prevented the recrystallization of PEO upon sitting at ambient environment. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1530–1540, 2006     

Synthesis of polymer gel electrolyte with high molecular weight poly(methyl methacrylate)-clay nanocomposite

Polymer nanocomposite gel electrolytes consisting of high molecular weight poly(methyl methacrylate) PMMA-clay nanocomposite, ethylene carbonate (EC)/propylene carbonate (PC) as plasticizer, and LiClO₄ electrolyte are reported. Montmorillonite clay was ion exchanged with a zwitterionic surfactant (octadecyl dimethyl betaine) and dispersed in methyl methacrylate, which was then polymerized to synthesize PMMA-clay nanocomposites. The nanocomposite was dissolved in a mixture of EC/PC with LiClO₄, heated and pressed to obtain polymer gel electrolyte. X-ray diffraction (XRD) of the gels indicated intercalated clay structure with d-spacings of 2.85 and 1.40 nm. In the gel containing plasticizer, the clay galleries shrink suggesting intercalation rather than partial exfoliation observed in the PMMA-clay nanocomposite. Ionic conductivity varied slightly and exhibited a maximum value of 8 × 10⁻⁴ S/cm at clay content of 1.5 wt.%. The activation energy was determined by modeling the conductivity with a Vogel-Tamman-Fulcher expression. The clay layers are primarily trapped inside the polymer matrix. Consequently, the polymer does not interact significantly with LiClO₄ electrolyte as shown by FTIR. The presence of the clay increased the glass transition temperature (Tg) of the gel as determined by differential scanning calorimetry. The PMMA nanocomposite gel electrolyte shows a stable lithium interfacial resistance over time, which is a key factor for use in electrochemical applications.     

Composite polymer electrolytes based on the low crosslinked copolymer of linear and hyperbranched polyurethanes

Low crosslinked copolymer of linear and hyperbranched polyurethane (CHPU) was prepared, and the ionic conductivities and thermal properties of the composite polymer electrolytes composed of CHPU and LiClO₄ were investigated. The FTIR and Raman spectra analysis indicated that the polyurethane copolymer could dissolve more lithium salt than the corresponding polymer electrolytes of the non crosslinked hyperbranched polyurethane, and showed higher conductivities. At salt concentration EO/Li = 4, the electrolyte CHPU30‐LiClO₄ reached its maximum conductivity, 1.51 × 10^?5 S cm^?1 at 25°C. DSC measurement was also used for the analysis of the thermal properties of polymer electrolytes. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 3607–3613, 2007     

Characterization of PEO-PAN hybrid solid polymer electrolytes

Hybrid solid polymer electrolytes (HSPE) of high ionic conductivity were prepared using polyethylene oxide (PEO), polyacrylonitrile (PAN), propylene carbonate (PrC), ethylene carbonate (EC), and LiClO₄. These electrolyte films were dry, free standing, and dimensionally stable. The HSPE films were characterized by constructing symmetrical cells containing nonblocking lithium electrodes as well as blocking stainless steel electrodes. Studies were made on ionic conductivity, electrochemical reaction, interfacial stability, and morphology of the films using alternating current impedance spectroscopy, infrared spectroscopy, and scanning electron microscopy. The properties of HSPE were compared with the films prepared using (i) PEO, PrC, and LiClO₄; and (ii) PAN, PrC, EC, and LiClO₄. The specific conductivity of the HSPE films was marginally less. Nevertheless, the dimensional stability was much superior. The interfacial stability of lithium was similar in the three electrolyte films. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65: 2191–2199, 1997