Amphiphilic polymer gel electrolytes. I. preparation of gels based on poly(ethylene oxide) graft copolymers containing different ionophobic groups

Amphiphilic graft copolymers were prepared via the radical copolymerization of poly(ethylene oxide) (PEO) macromonomers with fluorocarbon or hydrocarbon acrylates in toluene with 2,2′‐azobisisobutyronitrile (AIBN) as an initiator. ¹H NMR spectroscopy confirmed that the composition of the graft copolymers corresponded well to the monomer feed. For gel electrolytes prepared from the amphiphilic copolymers, the nature of the ionophobic parts of the amphiphilic graft copolymers had a great influence on the ion conductivity. Gel electrolytes based on graft copolymers containing fluorocarbon side chains showed significantly higher ion conductivity than electrolytes based on graft copolymers containing hydrocarbon groups. The ambient‐temperature ion conductivity was about 2.6 mS/cm at 20 °C for a gel electrolyte based on an amphiphilic graft copolymer consisting of an acrylate backbone carrying PEO and fluorocarbon side chains. Corresponding gels based on graft copolymers with PEO side chains and hydrocarbon groups showed an ambient‐temperature ion conductivity of about 1.2 mS/cm. The gel electrolytes contained 30 wt % copolymer and 70 wt % 1 M LiPF₆ in an ethylene carbonate/γ‐butyrolactone (2/1 w/w) mixture. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2223–2232, 2001     

Synthesis and properties of all solid polymer electrolytes based on poly(vinyl acetate‐co‐acetyl ethylene oxide acrylate)

Poly(acetyl ethylene oxide acrylate‐co‐vinyl acetate) (P(AEOA‐VAc)) was synthesized and used as a host for lithium perchlorate to prepare an all solid polymer electrolyte. Introduction of carbonyl groups into the copolymer increased ionic conductivity. All solid polymer electrolytes based on P(AEOA‐VAc) at 14.3 wt% VAc with 12wt% LiClO₄ showed conductivity as high as 1.2 × 10^?4 S cm^?1 at room temperature. The temperature dependence of the ionic conductivity followed the VTF behavior, indicating that the ion transport was related to segmental movement of the polymer. FTIR was used to investigate the effect of the carbonyl group on ionic conductivity. The interaction between the lithium salt and carbonyl groups accelerated the dissociation of the lithium salt and thus resulted in a maximum ionic conductivity at a salt concentration higher than pure PAEO‐salts system. Copyright © 2010 John Wiley & Sons, Ltd.     

Nanostructure,interactions, and conductivities of polymer electrolytes comprising silver salt and microphase‐separated graft copolymer

Silver polymer electrolytes were prepared by blending silver salt with poly(oxyethylene)₉ methacrylate)‐graft‐poly(dimethyl siloxane), POEM‐g‐PDMS, confining silver salts within the continuous ion‐conducting POEM domains of microphase‐separated graft copolymer. AgClO₄ polymer electrolytes exhibited their maximum conductivity at high silver concentrations as well as higher ionic conductivities than AgCF₃SO₃ electrolytes. The difference in conductivities of the two electrolytes was investigated in terms of the differences in the interactions of silver ions with ether oxygen of POEM and, hence, with the anions of salts. Upon the addition of salt in graft copolymer, the increase of T_g in AgClO₄ was higher than that in AgCF₃SO₃ electrolytes. Analysis of an extended configuration entropy model revealed that the interaction of ether oxygen/AgClO₄ was stronger than that of ether oxygen/AgCF₃SO₃ whereas the interaction of Ag⁺/ClO₄^? was weaker than that of Ag⁺/CF₃SO₃^?. These interactions are supported by the anion vibration mode of FT‐Raman spectroscopy. It is thus concluded that the higher ionic conductivity of AgClO₄ electrolytes was mostly because of higher concentrations of free ions, resulting from their strong ether oxygen/silver ion and weak silver ion/anion interactions. A small angle X‐ray scattering study also showed that the connectivity of the POEM phase was well developed to form nanophase morphology and the domain periodicities of graft copolymer electrolytes monotonically increased with the increase of silver concentration up to critical concentrations, after which the connectivity was less developed and the domain spacings remained invariant. This is attributed to the fact that silver salts are spatially and selectively incorporated in conducting POEM domains as free ions up to critical concentrations, after which they are distributed in both domains as ion pairs without selectivity. The increase of domain d‐spacing in AgClO₄ electrolytes was larger than that in AgCF₃SO₃, which again results from high concentrations of free ions in the former. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1018–1025, 2007     

Phase behavior and Li+ Ion conductivity of styrene‐ethylene oxide multiblock copolymer electrolytes

Solid polymer electrolytes are attractive materials for use as battery separators. Here, a molecular weight series of polystyrene–polyethylene oxide (PEO) multiblock copolymers was synthesized by the thiol–norbornene click reaction. The subsequent materials were characterized both neat and with a lithium bis‐(trifluoromethane)sulfonimide salt loading [(Li)/(EO)] of 0.1. In general, neat samples demonstrated crystallinity scaling with PEO content. Lithium ion‐containing samples had broad scattering peaks, half of which displayed disordered scattering, even at the lowest block molecular weights (polystyrene = 1 kg/mol, PEO = 1 kg/mol). Fitting of disordered scattering data, using the random phase approximation, yielded χ_RPA and R_g values that were compared with recent predictive work by Balsara and coworkers. The predictions were accurate near the volume fraction f_PEO = 0.5 but deviated symmetrically with volume fraction asymmetry. Samples were also analyzed by electrochemical impedance spectroscopy for their potential to conduct lithium ions. Samples with f_PEO ≥ 0.5 demonstrated robust conductivity, whereas samples below this volume fraction conducted very poorly, with one exception (f_PEO = 0.24). This work expanded upon our recently reported approach to multiblock copolymer synthesis, demonstrating the improved access of materials to further our fundamental understanding of multiblock copolymers. Copyright © 2016 John Wiley & Sons, Ltd.     

Solid polymer electrolytes. IV. Preparation and characterization of novel crosslinked epoxy‐siloxane polymer complexes as polymer electrolytes

Two series of novel crosslinked siloxane‐based polymers and their complexes with lithium perchlorate (LiClO₄) were prepared and characterized by Fourier transform infrared spectroscopy, solid‐state NMR (¹³C, ²⁹Si, and ⁷Li nuclei), and differential scanning calorimetry. Their thermal stability and ionic conductivity of these complexes were also investigated by thermogravimetric and AC impedance measurements. In these polymer networks, poly(propylene oxide) chains with different molecular weights were introduced through self‐synthesized epoxy‐siloxane precursors cured with two curing agents. The glass‐transition temperature (T_g) of these copolymers is dependent on the length of the ether units. The dissolution of LiClO₄ considerably increases the T_g of the polyether segments. The dependence of the ionic conductivity was investigated as a function of temperature, LiClO₄ concentration, and the molecular weight of the polyether segments. The ion‐transport behavior was affected by the combination of the ionic mobility and number of carrier ions. The ⁷Li solid‐state NMR line shapes of these polymer complexes suggest a significant interaction between Li⁺ ions and the polymer matrix, and temperature‐ and LiClO₄ concentration‐dependent chemical shifts are correlated with ionic conductivity. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1226–1235, 2002     

Effect of side‐chain length on the electrospinning of perfluorosulfonic acid ionomers

The effect of the side‐chain length (short side chain and long side chain, SSC and LSC, respectively) of perfluorosulfonic acid (PFSA) ionomers on the properties of nanofibers obtained by electrospinning ionomer dispersions in high dielectric constant liquids has been investigated with a view to obtaining electrospun webs as components of fuel cell membranes. Ranges of experimental conditions for electrospinning LSC and SSC PFSAs have been explored, with a scoping of solvents, carrier polymer and PFSA ionomer concentrations, and carrier polymer molecular weight. Under optimal conditions, the electrospun mats derived from SSC and from LSC PFSA show distinct fiber dimensions that arise from the different chain lengths of the respective ionomers. Enhanced interchain interactions in SSC PFSA with low equivalent weight compared to LSC PFSA result in a considerably lower average fiber diameter and a markedly narrower fiber size distribution. The proton conductivity of nanofiber mats of SSC and LSC PFSA with equivalent weights of 830 and 900 g mol^?1, respectively, are 102 and 58 mS cm^?1 at 80°C and 95% relative humidity. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Brush‐First ROMP of poly(ethylene oxide) macromonomers of varied length: impact of polymer architecture on thermal behavior and Li+ conductivity

The properties of polymeric materials are dictated not only by their composition but also by their molecular architecture. Here, by employing brush‐first ring‐opening metathesis polymerization (ROMP), norbornene‐terminated poly(ethylene oxide) (PEO) macromonomers ( MM‐n , linear architecture), bottlebrush polymers ( Brush‐n , comb architecture), and brush‐arm star polymers ( BASP‐n , star architecture), where n indicates the average degree of polymerization (DP) of PEO, are synthesized. The impact of architecture on the thermal properties and Li⁺ conductivities for this series of PEO architectures is investigated. Notably, in polymers bearing PEO with the highest degree of polymerization, irrespective of differences in architecture and molecular weight (~100‐fold differences), electrolytes with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) as an Li⁺ source exhibit normalized ionic conductivities (σ_n) within only 4.9 times difference (σ_n = 29.8 × 10^?5 S cm^?1 for MM‐45 and σ_n = 6.07 × 10^?5 S cm^?1 for BASP‐45 ) at a concentration of Li⁺ r = [Li⁺]/[EO] = 1/12 at 50 °C. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 448–455     

Synthesis of organic sulfobetaine‐based polymer gel electrolyte for dye‐sensitized solar cell application

We have synthesized eco‐friendly, economic, and equally efficient polysulfobetaine‐based gel electrolyte to the alternative of liquid electrolyte in the fabrication of dye‐sensitized solar cells (DSSCs) for the first time. This nitrogen‐rich and highly conductive polysulfobetaine was synthesized by an easy and facile method without the use of any catalyst and explored for its DSSC application. The synthesized polymer gel electrolyte exhibited good ionic conductivity about 6.8 × 10^?3 Scm^?1 at ambient temperatures. DSSCs were fabricated based on this polysulfobetaine gel electrolyte and studied for their performance based on photovoltaic parameters. The DSSC photovoltaic results were appreciable and are Voc = 0.82 V, Jsc = 11.49 mA/cm², FF = 66%, and PCE = 6.26% at 1 sun intensity. These values are slightly lower than conventional liquid electrolyte‐based DSSC shown as Voc = 0.78 V, Jsc = 12.90 mA/cm², FF = 69%, and PCE = 7.07%, both at 100 mWcm^?2. Conductivity and photovoltaic parameters of the device reveals that as prepared polysulfobetaine‐based polymer gel electrolyte may be useful in the fabrication of DSSC and other electrochemical devices. Copyright © 2017 John Wiley & Sons, Ltd.     

Dielectric relaxation and ionic transport in poly(ethylene carbonate)‐based electrolytes

To study the ion‐conductive and dielectric properties of polymer electrolytes based on poly(ethylene carbonate) (PEC) with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), the complex permittivity and conductivity were measured using broadband dielectric spectroscopy. The temperature dependence of the relaxation frequency and ionic conductivity for PEC‐LiTFSI electrolytes (1 – 200 mol%) indicates that the segmental motion of PEC chains decreases with the addition of just 1 mol% of Li salt and increases with increasing concentration above 10 mol%. According to the Walden rule for PEC‐based electrolytes, the value of deviation from the reference line increased, and the fragility and decoupling exponents decreased with increasing salt concentration. These results indicate that there are large numbers of ion pairs and aggregated ions, which imply low ionicity and reduced fragility in highly concentrated PEC‐based electrolytes. Copyright © 2016 John Wiley & Sons, Ltd.     

Solution‐crystallization and related phenomena in 9,9‐dialkyl‐fluorene polymers. II. Influence of side‐chain structure

Solution‐crystallization is studied for two polyfluorene polymers possessing different side‐chain structures. Thermal analysis and temperature‐dependent optical spectroscopy are used to clarify the nature of the crystallization process, while X‐ray diffraction and scanning electron microscopy reveal important differences in the resulting microstructures. It is shown that the planar‐zigzag chain conformation termed the β‐phase, which is observed for certain linear‐side‐chain polyfluorenes, is necessary for the formation of so‐called polymer‐solvent compounds for these polymers. Introduction of alternating fluorene repeat units with branched side‐chains prevents formation of the β‐phase conformation and results in non‐solvated, i.e. melt‐crystallization‐type, polymer crystals. Unlike non‐solvated polymer crystals, for which the chain conformation is stabilized by its incorporation into a crystalline lattice, the β‐phase conformation is stabilized by complexation with solvent molecules and, therefore, its formation does not require specific inter‐chain interactions. The presented results clarify the fundamental differences between the β‐phase and other conformational/crystalline forms of polyfluorenes. © 2015 The Authors. Journal of Polymer Science Part B: Polymer Physics published by Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 1492–1506     

Synthesis and properties of poly(ethylene oxide)‐grafted polyethylene copolymer and terpolymer

A series of graft copolymers were synthesized based on ethylene‐co‐m,p‐methylstyrene (EMS) (backbone copolymer), ethylene‐1‐hexene‐m,p‐methylstyrene (EHMS) (backbone terpolymer), and polyethylene glycol monomethyl ethers (PEGM) (grafts) in this study. The PEGMs with molecular weights of 750 and 2000 were used. The chemical composition of the graft copolymers was analyzed by NMR and DSC measurements. The graft copolymers exhibited a phase‐separated morphology with the backbone and the methoxy polyethylene glycol (MPEG) grafts forming separate crystalline phases. The MPEG phase had a melting temperature lower than the corresponding MPEG homopolymer, as determined by DSC. The melting point of the crystalline phase formed by the EMS and EHMS main chains was lower than that of pure polymer backbone. Copyright © 2009 John Wiley & Sons, Ltd.     

Structural changes of silver polymer electrolytes: Comparison between poly(2‐ethyl‐2‐oxazoline) and poly(N‐vinyl pyrrolidone) complexes with silver salt

The difference between the polymer matrices of poly(2‐ethyl‐2‐oxazoline) (POZ) and poly(N‐vinyl pyrrolidone) (PVP) does not have a significant effect on the facilitated propylene transport and propylene solubility in 1:1 polymer/silver salt complex membranes, according to our previous work. In this article, its origin is investigated in terms of both microstructures of silver polymer electrolytes and the coordinative interaction of silver ion with polymer and with the counteranion. Initially different microstructures of POZ and PVP become similar to each other upon dissolving a large amount of silver salt, as evidenced by propane transport properties, specific volume, and Bragg d‐spacing. The dissolution of the silver salt in the polymer solvent strongly depends on the coordinative interaction between silver ion and carbonyl oxygen of POZ and PVP. Thus, the structural similarity upon dissolving silver salts in POZ and PVP is primarily determined by the coordinative interaction between silver ion and carbonyl oxygen, which was confirmed by theoretical structure calculation based on density functional theory and by IR and Raman spectroscopy. Therefore, facilitated olefin transport for silver polymer electrolyte membranes does not strongly depend on the polymeric matrix at high silver concentrations. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 232–237, 2004     

Preparation and ionic conductivities of the plasticized polymer electrolytes based on poly(methyl methacrylate-co-alkali metal methacrylate)

Ionic conductivities of the polymer electrolytes prepared from the ionomer (poly(methyl methacrylate-co-alkali metal methacrylate)), lithium perchlorate, and ethylene carbonate as a plasticizer, were studied as a function of the ion content and the alkali-metal cation of the ionomer. It was possible to obtain tough films with room-temperature ionic conductivities of ∼ 10^-3 S/cm. The maximum ion conductivities of the polymer electrolytes were obtained at the ion content of 5 mol % for both Li and Na ionomer. The effects of the ion content of the ionomer on the ionic conductivities of the polymer electrolytes were mainly interpreted in terms of the characteristics of the ion aggregate formed in the polymer electrolytes. The thermal dependence of the ionic conductivity was shown to be a non-VTF pattern in some of the polymer electrolytes investigated, which is expected to be due to the presence of the ion aggregate. © John Wiley & Sons, Inc.     

Synthesis and characterization of polymer electrolytes based on cross‐linked phenoxy‐containing polyphosphazenes

A new method to prepare the polymer electrolytes for lithium‐ion batteries is proposed. The polymer electrolytes were prepared by reacting poly(phosphazene)s (MEEPP) having 2‐(2‐methoxyethoxy)ethoxy and 2‐(phenoxy)ethoxy units with 2,4,6‐tris[bis(methoxymethyl)amino]‐1,3,5‐triazine (CYMEL) as a cross‐linking agent. This method is simple and reliable for controlling the cross‐linking extent, thereby providing a straightforward way to produce a flexible polymer electrolyte membrane. The 6 mol % cross‐linked polymer electrolyte (ethylene oxide unit (EO)/Li = 24:1) exhibited a maximum ionic conductivity of 5.36 × 10^?5 S cm^?1 at 100 °C. The ⁷Li linewidths of solid‐state static NMR showed that the ionic conductivity was strongly related to polymer segment motion. Moreover, the electrochemical stability of the MEEPP polymer electrolytes increased with an increasing extent of cross‐linking, the highest oxidation voltage of which reached as high as 7.0 V. Moreover, phenoxy‐containing polyphosphazenes are very useful model polymers to study the relationship between the polymer flexibility; that is, the cross‐linking extent and the mobility of metal ions. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 352–358     

Regularity modes in Raman spectra of polyolefins: Part II. Polyethylene and ethylene copolymers

In this work, the thermal behavior of the regularity modes in Raman spectra of polyethylene with different densities and random ethylene/1-hexene copolymers with varying content of comonomer are studied. We demonstrate especially that the vibrational modes at 1062 and 2850 cm^↙1 are related to a critical sequence length of trans-conformers of 6⬜8 CH₂ groups, while the modes at 1130, 1170, 1295, and 2883 cm^↙1 indicate a critical sequence length of trans-conformers of 18 CH₂ groups. Upon increasing the 1-hexene content in the ethylene/1-hexene copolymers, the evolution of the intensities of the Raman modes at 1062, 1130, 1170, 1295, and 1417 cm^↙1, normalized to the intensity of the band at 2850 cm^↙1, is similar to the evolution of the intensities of the same modes in the Raman spectra of low density polyethylene at increasing temperature. This observation however contrasts with that in the Raman spectra of polyethylenes with middle and high densities. We suppose that these results can be explained by similarities in the structure of non-crystalline areas of low density polyethylene and the ethylene/1-hexene copolymers, which contain significant amounts of short sequences of trans-conformers.     

Graft copolymers having hydrophobic backbone and hydrophilic branches. X. Preparation and properties of water-dispersible polyanionic microspheres having poly(methacrylic acid) branches on their surfaces

The free radical copolymerization of poly(t-butyl methacrylate) (PBMA) macromonomer with styrene in ethanol give monodispersed microspheres with 0.8-1.6 μm diameter. The resulting microspheres were treated with HCl solution to convert into anionic microspheres having poly(methacrylic acid) chains. ESCA analysis of the microsphere surface suggested that PBMA chains were favorably located on the surface of the microspheres. The particle size of the microspheres decreased with increasing molecular weight and concentration of the macromonomer. Water dispersibilities of the microspheres were evaluated by measuring the relative turbidity of the suspension of microspheres as a function of pH. The results show that they were strongly dependent on pH. © 1995 John Wiley & Sons, Inc.     

Amphiphilic polymer electrolytes consisting of PVC‐g‐POEM comb‐like copolymer and LiCF3SO3

An amphiphilic comb‐like copolymer consisting of a poly(vinyl chloride) (PVC) backbone and poly((oxyethylene)₉ methacrylate) (POEM) side chains, PVC‐graft‐POEM was synthesized via atom transfer radical polymerization. This comb copolymer was complexed with LiCF₃SO₃ to form a solid polymer electrolyte. FTIR and FT‐Raman spectroscopy indicate that lithium salts are dissolved in the ion conducting POEM domains of microphase‐separated graft copolymer up to 10 wt % of salt concentration. Microphase‐separated structure of the materials and the selective interaction of lithium ions with POEM domains were revealed by transmission electron microscopy, wide angle X‐ray scattering, and differential scanning calorimetry. The maximum ionic conductivity of 4.4 × 10^?5 S/cm at room temperature was achieved at 10 wt % of salt concentration, above which salts are present as less mobile species such as ion pairs and higher order ionic aggregates, as characterized by FT‐Raman spectroscopy. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1443–1451, 2009     

Molecular dynamics simulation of polymer electrolytes based on poly(ethylene oxide) and ionic liquids. II. Dynamical properties

Dynamical properties of polymer electrolytes based on poly(ethylene oxide) (PEO) and ionic liquids of 1-alkyl-3-methylimidazolium cations were calculated by molecular dynamics simulations with previously proposed models [L. T. Costa and M. C. Ribeiro, J. Chem. Phys. 124, 184902 (2006)]. The effect of changing the ionic liquid concentration, temperature, and the 1-alkyl-chain lengths, [1,3-dimethylimidazolium]PF(6) and [1-butyl-3-methylimidazolium]PF(6) ([dmim]PF(6) and [bmim]PF(6)), was investigated. Cation diffusion coefficient is higher than those of anion and oxygen atoms of PEO chains. Ionic mobility in PEO[bmim]PF(6) is higher than in PEO[dmim]PF(6), so that the ionic conductivity kappa of the former is approximately ten times larger than the latter. The ratio between kappa and its estimate from the Nernst-Einstein equation kappa/kappa(NE), which is inversely proportional to the strength of ion pairs, is higher in ionic liquid polymer electrolytes than in polymer electrolytes based on inorganic salts with Li(+) cations. Calculated time correlation functions corroborate previous evidence from the analysis of equilibrium structure that the ion pairs in ionic liquid polymer electrolytes are relatively weak. Structural relaxation at distinct spatial scales is revealed by the calculation of the intermediate scattering function at different wavevectors. These data are reproduced with stretched exponential functions, so that temperature and wavevector dependences of best fit parameters can be compared with corresponding results for polymer electrolytes containing simpler ions.     

An Efficient Thiol‐Ene Chemistry for the Preparation of Amphiphilic PHA‐Based Graft Copolymers

We present a straightforward method to prepare amphiphilic graft copolymers consisting of hydrophobic poly(3‐hydroxyalkanoates) (PHAs) backbone and hydrophilic α‐amino‐ω‐methoxy poly(oxyethylene‐co‐oxypropylene) (Jeffamine®) units. Poly(3‐hydroxyoctanoate)‐co‐(3‐hydroxyundecenoate) (PHOU) was first methanolyzed to obtain the desired molar mass. The amino end groups of Jeffamine were converted into thiol by a reaction with N‐acetylhomocysteine thiolactone and subsequently photografted. This “one‐pot” functionalization prevents from arduous and time‐consuming functionalization of the hydrophilic precursor or tedious modifications of PHAs, thus simplifying the process. The amphiphilic nature of modified PHAs leads to water‐soluble copolymers exhibiting thermoresponsive behavior.     

Gel polymer electrolytes prepared with porous membranes based on an acrylonitrile/methyl methacrylate copolymer

Porous membranes based on acrylonitrile/methyl methacrylate copolymer were prepared by a phase‐inversion method. Microstructures of the porous membranes were controlled through the variation of the evaporation drying time before immersion in a nonsolvent bath. Gel polymer electrolytes were prepared from these porous membranes via soaking in an organic electrolyte solution. They encapsulated the electrolyte solution well without solvent leakage and maintained good mechanical properties that allowed the preparation of thin films (～23 μm). These systems showed acceptable ionic conductivity values (>6.0 × 10^?4 S/cm) at room temperature and sufficient electrochemical stability over 4.4 V that allowed applications in lithium‐ion polymer batteries. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1496–1502, 2002