Design of Single Ionic Conduction in Polymeric Solid Electrolytes

Oligo(oxyethylene) methacrylate, MEO, has been synthesized as a basic material to design a polymeric solid electrolyte. The homopolymer P(MEO) has a glass transition temperature of -78°C. P(MEO) solubilizes inorganic salts without solvent, and the dissociated ions migrate fast to give very high ionic conductivity, above 10^?5 S/cm for ac. Although the ac conductivity is high, the current decreases gradually under dc conditions. This is improved by the design of an ionic conductor using only cations. Poly[oligo(oxyethylene) methacrylate-co-alkali metal methacrylate], P(MEO-MAM), is prepared as an organic solid electrolytes which allows cationic single-ion conduction. The ionic conductivity of the films depends on the electrolyte content, the dissociation energy of the comonomeric electrolytes, and the degree of segmental motion surrounding the ions in the polymer matrix. The ionic conductivity of Li or K is around 10^?6 S/cm in these polymeric systems at 80°C. The plot of logarithmic conducticity vs reciprocal absolute temperature is a curved line. The Williams-Landel-Ferry parameters, calculated from the temperature dependence of the conductivity, coincided with theoretical values within a certain range. The single-ion conduction in these films is concluded to be affected considerably by the segmental motion of the matrix polymer. This is also confirmed by the Vogel-Tammann-Fulcher plot.     

CATIONIC CONDUCTIVITY FOR THE CROSSLINKED P [OLIGO (OXYETHYLENE) METHACRYLATE-COoMETHACRYLOYL ALKYLSULFONIC ACID LITHIUM]

Crosslinked copolymers with single Li~+-ionic conductivity were prepared from oligo (oxyethylene) methacrylate (MEO_n), methacryloyl alkylsulfonic acid lithium (SAMLi), and oligo (oxyethylene) dimethacrylate (DMEO_n). Li~+-ionic conductivity of the copolymer is improved by crosslinking and presented as a function of polymerization degree (n) in MEO_n, comonomeric salt concentration (O/Li), and crosslinking degree. The crosslinked copolymer P (0.7 MEO_(14)-0.3DMEO_(14)-SHMLi) without other small molecular additives exhibits an optimum Li~+-ionic conductivity of 1.2×10~(-6) S/cm at 25℃. Dc polarization test in the cell composed of Li/copolymer/Li shows a constant dc ionic conductivity which closes gradually to the ac one with decreasing dc polarization potential.     

Alkali salts of (ω-sulphoxyalkyl)-acrylates and -methacrylates: Radical polymerization and copolymerization

A new preparation of alkali salts of (ω-sulphoxyalkyl)-acrylates and -methacrylates, by reaction of alkali salts of acrylic and methacrylic acids with cyclic sulphates, is described; spectral characterization of the products is described. The kinetics of the radical polymerization of sodium (2-sulphoxyethyl)methacrylate (SSEM) were studied; monomer reactivity ratios for copolymerization with methacrylic acid were: r₁ = 1.1 ± 0.15 and r₂ = 0.73 ± 0.05. Dark electrical surface conductivity of some homopolymers and copolymers with methacrylic acid was found to be 10⁴–10¹¹$\text{Ω}{}^{\mathrm{?1}}$, depending on relative humidity.     

Microstructural Characterization of Diblock Copolymers Formed by Styrene and Different Methacrylic Units

FT-IR, DSC, and NMR techniques allowed the structural characterization of four copolymers formed by styrene and methacrylic units (methacrylic acid (MAA), dimethylamine ethyl methacrylate (DMAEMA), sodium methacrylate (MANa), and 1-hydroxyethyl methacrylate (HEMA). The copolymer composition was studied by Fourier transform-infrared spectroscopy (FT-IR) and nuclear magnetic resonance (NMR) spectroscopy. The thermal behavior of the block copolymers was analyzed by differential scanning calorimetry (DSC). Three of the four copolymers showed two transitions caused by changes in the polymer heat capacity (ΔCp) of each block. Diffusion-ordered spectroscopy (DOSY) experiments were used to distinguish copolymer from homopolymer mixtures. Finally, the triad-level stereosequences of styrene-methacrylic copolymers were obtained using ¹³C NMR. The results indicate that by increasing the alkyl-substituent length in the methacrylic block, the probability of syndiotactic polymerization increases.     

Specific ionic conduction in poly[oligo (oxyethylene glycol) methacrylate] (PMEO)–Li salt complexes under high‐pressure CO2

We measured the ionic conductivity of amorphous poly[oligo (oxyethylene glycol) methacrylate] (PMEO)–lithium salt complexes under a CO₂ pressure varying from 0.1 to 20 MPa. The pressure dependence of the conductivity was positive, and the conductivity was higher than that under an inert gas such as N₂. The ion‐conductive behavior has been modeled using both the Vogel–Tammann–Fulcher (VTF) equation and activation volume theory. The calculated parameters of the VTF equation show that CO₂ that had permeated into the PMEO matrix acts as solvent molecules to dissolve ions and lower the glass transition temperature at high pressures. The ionic conduction in PMEO complexes under high‐pressure CO₂ was scarcely related to the VTF parameters and activation volume equations. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 3151–3158, 2005     

Fluorescence characteristics of europium ions stabilized in solid polymer electrolytes containing polyether structure

Polyethylene oxide (PEO) oligomers can dissolve lanthanide salts. The terminal hydroxyl groups of PEO affect the solubility of the lanthanide salts in the PEO considerably. However, no intensive fluorescence was observed from Eu³⁺ dispersed in PEO or other ion-conductive polymers containing terminal hydroxyl groups, because of the quenching effect of the terminal hydroxyl groups. Copolymer of ω-methoxy oligo(oxyethylene) methacrylate and methyl methacrylate (P(MEOM-co-MMA)) could dissolve small amount of Eu(NO₃)₃, but the copolymer film containing Eu³⁺ shows intensive fluorescence (Ex = 269.0 nm, Em = 570.0 nm). This was prepared as a soft film, and there was a clear dependence of the Eu³⁺ concentration on the fluorescence intensity. A linear relation between the film thickness and the fluorescence intensity was also observed. Little fluorescence was found for Eu³⁺ in the blend of the corresponding two homopolymers, i.e. poly-(ω-methoxy oligo (oxyethylene) methacrylate) (PMEOM) and poly(α-methyl methacrylate) (PMMA). This strongly suggests that intensive fluorescence requires a mixed state of MEOM and MMA units at molecular level.     

Synthesis of triblock and multiblock methacrylate polymers and self‐assembly of stimuli responsive triblock polymers

Multisegmented poly(methacrylate)s were synthesized using one pot reversible addition fragmentation chain transfer polymerization. Initially, a series of triblock copolymers were synthesized with different ratios of trimethylsilyl methacrylate, di(ethylene oxide) methacrylate, and oligo(ethylene oxide) methacrylate, and different total polymer molecular weights. Additionally, a polymer containing seven distinct blocks of methacrylic monomers was synthesized in one pot. For the triblock copolymers, the trimethylsilyl group was subsequently hydrolyzed, and the self‐assembly of the triblock copolymer was studied in water, under different pH and thermal conditions. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 2548–2555     

Solubility, diffusion coefficient and ionic conductivity of alkyl viologens in poly(ethylene oxide) and its derivatives

A series of alkyl viologens RV (R denotes ethyl, butyl, hexyl, heptyl, and dodecyl) was dissolved in poly(ethylene oxide) (PEO) oligomers (average molar masses of 200, 300, 400, 600 and 1000 g mol⁻¹). The solubility of RV in PEO oligomers decreased with increasing alkyl chain length of RV and the molar mass of PEO. Cyclic voltammograms of RV in PEO containing 0.50 M LiClO₄ clearly show two redox waves. The ionic conductivity of PEO oligomers containing RV decreased with increasing alkyl chain length, suggesting the migration of RV itself in the PEO oligomers. Potential step chronoamperometry was used to obtain the apparent diffusion coefficient of RV in the PEO oligomers. The ionic conductivity has a linear relationship with the apparent diffusion coefficient regardless of the RV species, the PEO molar mass and the temperature. RV was shown to act as a redox mediator in PEO oligomers as long as the ionic conductivity of the PEO was high. Poly(oligo(oxyethylene) methacrylate) (PMEO) was used as a solid solvent for a series of alkyl viologens. Since PMEO is an excellent ion-conducting polymer, RV was confirmed to be an effective redox mediator in this PMEO. It was concluded in this study that ionic conductivity in the polymer matrix could be used as an effective parameter for prediction of the diffusion coefficient of charged organic molecules.     

Synthesis and polymerization of oligo(oxyethylene) macromonomer bearing sodium sulfonate

Oligo(oxyethylene) macromonomers bearing sodium sulfonate group have been synthesized through four reactions: (1) ring-opening polymerization of oxirane, (2) etherification of monomethoxyl oligo(oxyethylene) and epichlorohydrin, (3) sulfonation of cycloxyl compound, and (4) end-capping of sodium oligo(oxyethylene) sulfonate by methacrylic group. A desired length of oligo(oxyethylene) in the macromonomers can easily be achieved by controlling the ratio of reactants in the ring-opening step. The structures of the products of each reaction were identified by IR, ¹H-NMR, and GPC. Polymers of the monomers were also characterized by GPC and DSC. © 1993 John Wiley & Sons, Inc.     

THERMAL BEHAVIOR AND IONIC CONDUCTIVITY OF POLY[LITHIUM-N(4-SULFO-PHENYL) MALEIMIDE -CO-METHOXY OLIGO(OXYETHYLENE) METHACRYLATE]

Poly[lithium-N(4-sulfophenyl) maleimide -co- methoxy oligo-(oxyethylene) methacrylates] [P(LiSMOE_n)s] with three different oligoether side chains and different salt concentrations were synthesized. The copolyelectrolytes are essentially random in structure, with blocks of methoxy oligo(oxyethylene) meth-acrylate (MOE_nM) recurring sporadically in between the salt units of N(4-sulfophenyl) maleimide. They all show two glass transitions in the temperature range of ?100 to 100°C. The first one below ?30°C is assigned to the oligo(oxyethylene) side chain (T _g1), while the second one located between 20 and 50°C is attributed to the main chain of the polymer host (T _g2). The maximum ionic conductivity of the copolymer electrolytes, 1.6 × 10^?7 S cm^?1 at 25°C, occurs at lithium salt concentration [Li⁺]/[EO] = 2.2 mol%. The ionic conductive behavior of the copolyelectrolytes follows the Vogel-Tammann-Fulcher (VTF) equation. Moreover, a special VTF behavior exists in the copolymers with shorter oligoether side chain and higher salt concentration. Sweep voltammetric results indicate that these copolyelectrolytes have a good electrochemical stability window.     

Electroactive block copolymers

Synthesis, characterization and properties of microphase separated mixed (ionic and electronic) conducting or MIEC block copolymers are reported. Poly{[ω-methoxyocta(oxyethylene) methacrylate]-block-(4-vinylpyridine)}, abbreviated as P[MG8–4VP], and poly{(3-methylthiophene)-block-[(ω-methoxyocta(oxyethylene) methacrylate]}, abbreviated as P[3MT-MG8], have been synthesized. Differential scanning calorimetry (DSC) studies indicate that the polymers form a microphase separated structure. P[3MT-MG8] can be doped with I₂ and LiClO₄ to generate electronic and ionic conducting microdomains, respectively. For the P[3MT-MG8] series, bulk electronic conductivity as high as 1×10⁻³ S cm⁻¹ and bulk ionic conductivity as high as 6.6×10⁻⁷ S cm⁻¹ is observed at 30°C. This work represents a new concept in the area of electroactive polymers and should impact the microelectrochemical device industry.     

Effect of introducing acrylic and methacrylic acid groups on molecular relaxation of poly(ethyl methacrylate)

Dielectric and infrared data have been obtained over a wide temperature range on copolymers of ethyl methacrylate with methacrylic and acrylic acid synthesized by radical copolymerization. The dissociation energy ΔH⁰ for the acid dimer in the copolymer is estimated from the temperature dependence of the relaxation strength Δε_α of the α relaxation, which is associated with the glass transition. The value of δH⁰ obtained by this method is in fair agreement with that determined by infrared (IR) spectroscopy. The strength of the α relaxation and its activation energy are both increased by the incorporation of methacrylic acid units but are decreased by acrylic acid units. This behavior is attributed to the restriction of main-chain motions by hydrogen-bonded acid dimers in the copolymers with methacrylic acid and to the incorporation of more flexible links in the copolymers with acrylic acid. The β relaxation observed below the glass transition temperatures is almost unaffected by the incorporation of methacrylic acid.     

POLYMERIC IONIC CONDUCTORS MODIFIED WITH POLAR GROUPS:PART Ⅰ. IONIC CONDUCTION AND MECHANICAL PROPERTY OF LI-COMPLEX BASED ON ACRYLAM ID E-COPOLYMERIZED METHACRYLATES

Acrylamide was introduced onto the chain of poly[oligo(oxyethylene) methacrylate] as a polar constituent, and the effect of its presence on the mechanical strength and ionic conduction properties of Li-salt complex based on the resultant copolymer was investigated. The introduction of the polar constituent raises chain rigidity, retards crystallization of oligo(oxyethylene) domain and promotes the dissociation of lithium salt. The factors work on the mechanical and conduction properties synergistically, therefore both of the properties are improved simultaneously as the consequence of acrylamide-introduction.     

Controlled/“living” atom transfer radical polymerization of methyl methacrylate in the synthesis of triblock copolymers from a poly(oxyethylene) macroinitiator

Atom transfer radical polymerization of methyl methacrylate initiated by a poly(oxyethylene) macroinitiator by the esterification of PEG 1500 with 2-chloro propionyl chloride was synthesized. These polymerization proceeds both in bulk and solution with a quantitative initiation efficiency, leading to A-B-A triblock copolymers. The macroinitiators and their block copolymers were characterized by FT-IR, FT-NMR and GPC analyses. In bulk polymerization, the kinetic study showed that the relationship between ln[M]₀/[M] vs time was linear showing that there is a constant concentration of active species throughout the polymerization and follow the first order kinetics with respect to monomer. Moreover, the experimental molecular weight of the block copolymers increased linearly with the monomer conversion and the polydispersity index remained between 1.3 and 1.5 throughout the polymerization. No formation of homo poly(methyl methacrylate) could also be detected, and all this confirms that the bulk polymerization proceeds in a controlled/“living” manner.     

Point by point comparison of two thermosensitive polymers exhibiting a similar LCST: is the age of poly(NIPAM) over?

The present Communication compares the thermosensitivity in dilute aqueous solutions of well-defined copolymers composed of 95% of 2-(2-methoxyethoxy)ethyl methacrylate (MEO2MA) and 5% of oligo(ethylene glycol) methacrylate (OEGMA, Mn = 475 g.mol-1) and poly(N-isopropylacrylamide) (PNIPAM) samples having similar degrees of polymerization and chain-ends. The thermoresponsive behavior of P(MEO2MA-co-OEGMA) was found to be overall comparable, and in some cases, superior to PNIPAM. Hence, P(MEO2MA-co-OEGMA) copolymers can be considered as ideal structures, which combine both the properties of poly(ethylene glycol) and PNIPAM in a single macromolecule.     

Metal‐free synthesis of responsive polymers: Cloud point tuning by controlled “click” reaction

Nitroxide‐mediated radical polymerization has been used for the preparation of pentafluorostyrene (PFS) homopolymers and random copolymers of PFS and oligo(ethyleneglycol) methacrylate (OEGMA_8.5). The poly(pentafluorostyrene) homopolymers were reacted with thiophenol at different ratios at room temperature in the presence of triethylamine. The “clicked” polymers were characterized by ¹H and ¹⁹F NMR spectroscopy and size exclusion chromatography. Moreover, the copolymerization kinetics of the PFS and OEGMA_8.5 copolymers was followed, and the phase transition behavior of random copolymers with different compositions was discussed. Furthermore, copolymers of PFS and 2‐(dimethylamino) ethyl methacrylate (DMAEMA) were prepared at various mole ratios, and the copolymer with a 10:90 ratio, respectively, was soluble in water at room temperature. Turbidimetry measurements were performed for PFS and OEGMA_8.5 or DMAEMA copolymers to determine their cloud points. Finally, the PFS and OEGMA_8.5 copolymer with a mole ratio of 60:40 was reacted further with thiophenol to increase the hydrophobic part in the copolymer. The cloud points of the obtained copolymers could be tuned from 87 to 33 °C by using not only the controlled radical polymerization but also the “click” reaction in a controlled fashion. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1278–1286, 2010     

Preparation and utilization of poly(methacryloylsilatrane) as a salt‐dissociation enhancer in PEO‐based polymer electrolytes

Polymers containing silatrane units were prepared by the free radical polymerization of methacryloylsilatrane (MPS), and their conductivities were evaluated. We confirmed that MPS can be polymerized without excessive decomposition of the silatrane units by the radical polymerization initiated by azobisisobutyronitrile. The chemical structure of the polymerized MPS (pMPS) was characterized by Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy, gel permeation chromatography, and matrix‐assisted laser desorption/ionization time‐of‐flight mass spectroscopy. The pMPS formed a homogeneous complex with lithium trifluoromethyl sulfonate (LiOTf), although the obtained pMPS/LiOTf complex did not show conductivity. The negligible conductivity was caused by the high glass transition temperature (T_g) of the pMPS matrix, which exceeded 70°C. The pMPS was subsequently utilized as a salt‐dissociation enhancer for the poly(ethylene oxide)‐based polymer electrolyte. MPS was copolymerized with poly[methacryloyl oligo(ethylene oxide)] (pMEO) by free radical polymerization. When the pMEO incorporated a small amount of MPS units (i.e. lower than 15 mol%), the elevation in T_g was not observed, and the conductivity markedly improved. Among the series of copolymers and when compared with pristine pMEO, the copolymer containing 6.3% of MPS units had the maximum conductivity (3.1 × 10^?4 S cm^?1 at 80°C). The Vogel–Fulcher–Tammann fitting parameters showed that the conductivity was improved by the increase in the number of carrier ions. The enhancement in salt dissociation was presumably due to the homogeneous incorporation of polar MPS units. However, when the MPS unit content exceeded 15 mol%, the conductivity was lowered because of the increase in T_g. Copyright © 2013 John Wiley & Sons, Ltd.     

POE incorporation into ionic clusters of ionomer and ion-conduction behaviors

Poly(oxyethylene) (POE) was incorporated into the ionic clusters of ionomers, ethylene and methacrylic acid (7.2% neutralized with KOH) copolymer membrane. The changes of properties were studied from SAXS, DSC, IR and ionic conductivity. The IR study suggested that the coordinated structures in ionic clusters of the membrane were destroyed by POE incorporation, and also SAXS suggested that ionic clusters were swollen by POE incorporation. The ionic conductivity, a carrier being K⁺ in this system, increases from 10^?16 S/cm to 10^?9 S/cm at 30°C by the incorporation of POE (20.5 wt%). On the other hand, a large amount of POE (63 wt%) could be incorporated into ionomer membrane by the esterification of methacrylic acid groups (93%) with POE. When LiClO₄ was added, ionic conduction occurred in the phase-separated POE domain, which had a low glass transition temperature (?55.2°C), showing an ionic conductivity 2.6 × 10^?6 S/cm at 25°C.     

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     

Synthesis,self‐assembly,and thermosensitivity of amphiphilic POEGMA‐PDMS‐POEGMA triblock copolymers

In this article, the synthesis and self‐assembly of a novel well‐defined biocompatible amphiphilic POEGMA‐PDMS‐POEGMA triblock copolymer were studied. The copolymer was synthesized by atom transfer radical polymerization of oligo(ethylene glycol) methyl ether methacrylate (OEGMA) using α,ω‐dibromo polydimethylsiloxane macroinitiator (Br‐PDMS‐Br). Br‐PDMS‐Br was synthesized through the esterification of α,ω‐hydroxypropyl polydimethylsiloxane and 2‐bromoisobutyryl bromide. The structures of the copolymers were confirmed by proton nuclear magnetic resonance spectroscopy, and gel permeation chromatography. The copolymers showed reversible aggregation in response to temperature cycles with a lower critical solution temperature (LCST) between 61 and 66 °C, as determined by ultraviolet‐visible spectrophotometry and dynamic light scattering. The LCST values increased in proportion to the length of the hydrophilic block and were lower than that of the POEGMA homopolymer. The self‐assembly behavior of the copolymers in aqueous solution was investigated by fluorescence spectroscopy and transmission electron microscopy. The critical micelle concentration value (1.08–0.26 10^?6 mol L^?1) decreased as the length of the POEGMA chain increased. The POEGMA‐PDMS‐POEGMA copolymers can easily self‐assemble into spherical micelles in aqueous solution. Such biocompatible block copolymers may be attractive candidates as ‘‘smart'' thermo‐responsive drug delivery systems. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 2684‐2691