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- Munch Elmér, Anette, et al.
(author)
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Gel electrolyte membranes derived from co-continuous polymer blends
- 2005
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In: Polymer. - : Elsevier BV. - 0032-3861. ; 46:19, s. 7896-7908
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Journal article (peer-reviewed)abstract
- Polymer gel electrolyte membranes were prepared by first casting films of poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) salt, and poly(ethylene glycol) (PEG) monomethacrylate and dimethacrylate macromonomers. Polymerization of the macromonomers initiated by UV-irradiation then generated solid films having phase-separated morphologies with a microporous PVDF-HFP phase embedded in PEG-grafted polymethacrylates. Gel electrolyte membranes were finally prepared by allowing the films to take up solutions of LiTFSI in gamma-butyrolactone (gamma-BL). The PEG-grafted polymethacrylate in the membranes was found to host the largest part of the liquid electrolyte, giving rise to a highly swollen ionic conductive phase. Results by FTIR spectroscopy showed that the Li+ ions preferentially interacted with the ether oxygens of the PEG chains. The properties of the membranes were studied as a function of the ratio of PVDF-HFP to PEG-grafted polymethacrylate, as well as the degree of crosslinking, LiTFSI concentration, and liquid electrolyte content. The self-supporting and elastic gel membranes had ionic conductivities of 10(-3) S cm(-1) and a mechanical storage modulus in the range of 2.5 MPa in the tension mode at room temperature. Variation of the salt concentration showed the greatest effect on the membrane properties.
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- Munch Elmér, Anette, et al.
(author)
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Ion Conductive Electrolyte Membranes Based on Co-Continuous Polymer Blends
- 2003
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In: Journal of Materials Chemistry. - : Royal Society of Chemistry (RSC). - 1364-5501. ; 13:9, s. 2168-2176
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Journal article (peer-reviewed)abstract
- Solid electrolyte membranes based on comb-shaped poly(ethylene glycol) (PEG) doped with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) salt in blends with poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) have been studied. Membranes containing between 70 and 100 wt% PEG were prepared by a convenient two-step process where films containing a mixture of mono- and dimethacrylate-terminated PEG macromonomers, PVDF-HFP, LiTFSI, and a photoactivator were cast from acetone solutions, followed by UV-initiated polymerization of the macromonomers. Microscopy of the membranes revealed a phase separated morphology with a microporous PVDF-HFP network embedded in comb-shaped PEG. The membranes were thermally stable at temperatures below the melting point of PVDF-HFP at 140 °C. Dynamic mechanical analysis (DMA) in the tension mode showed that the mechanical properties of the membranes were greatly improved both by the addition of PVDF-HFP and of dimethacrylate-terminated PEG macromonomer. For example, the storage modulus at 25 °C and 1 Hz showed a three-fold increase after increasing the percentage of dimethacrylate-terminated PEG from 0 to 10 wt% in the macromonomer mixture. A broad shoulder on tan as a function of temperature indicated the existence of a PVDF-HFP rich amorphous interphase. At room temperature, the membranes containing more than 80 wt% PEG reached ionic conductivities exceeding 10–5 S cm–1.
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| 4. |
- Munch Elmér, Anette
(author)
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Lithium Ion Conductive Membranes Based on Co-continuous Polymer Blends
- 2005
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Doctoral thesis (other academic/artistic)abstract
- There is a growing need for multifunctional polymeric materials for the development of several important energy conversion technologies. For example, the polymer electrolyte is a key component in lithium polymer batteries. The basic functions of this electrolyte are to efficiently conduct the lithium ions and physically separate the electrodes. Consequently, these electrolytes should ideally possess the ionic conductivity of a liquid while retaining the mechanical stability of a solid. In this thesis the concept of using polymer blends to obtain electrolyte membranes which combine ion conductivity and mechanical stability has been explored. The work comprises the preparation, characterisation and properties of three different lithium ion conductive membranes based on co-continuous polymer blend systems. The blend systems were all prepared from two polymeric components which were doped with a lithium salt. The main component was a salt-dissolving polymethacrylate network grafted with polyether or polyethercarbonate side chains. Two different kinds of methacrylate macromonomers were used in order to build up the graft copolymer structures. In two of the studied membrane types, poly(ethylene glycol) methacrylate macromonomers were used. In the third type, new polymeric building blocks, i.e., poly(ethylene carbonate-co-ethylene oxide) methacrylate macromonomers, were successfully synthesised via the anionic ring-opening polymerisation of ethylene carbonate. The macromonomers carried 30 mol% carbonate units in their structure. The minor component of the blends was a linear mechanically stable thermoplastic polymer which provided the dimensional stability. Poly(vinylidene fluoride-co-hexafluoropropylene) and poly(methyl methacrylate) were both investigated in this function. The electrolyte membranes were prepared by a two-step procedure, beginning with the solution casting of films of macromonomer, thermoplastic polymer, lithium salt and UV-activator. The methacrylate macromonomers were subsequently polymerised in-situ by UV-irradiation. The membranes were characterised by electron microscopy techniques, differential scanning calorimetry, Fourier transformation IR-spectroscopy, dynamic mechanical analysis, and electrochemical impedance spectroscopy to investigate the chemical composition, morphology, and the thermal, mechanical and conductive properties The membranes exhibited different phase separated morphologies, which depended on the level of salt content and crosslinking, as well as on the nature of the blend components. The strategy of blending polymeric materials to combine ionic conductivity with dimensional stability proved effective. The solid polymer electrolytes reached conductivities just above 10-5 S?cm-1 at room temperature while exhibiting a satisfying mechanical stability. Subsequent gelling of the solid membranes, by incorporating a liquid electrolyte of lithium salt dissolved in gamma-butyrolactone, gave elastic polymer gel electrolytes which reached conductivities of 10-3 S?cm-1 at room temperature. The studied membranes may potentially be used as electrolytes in different electrochemical devices such as lithium polymer batteries, electrochromic windows, and sensors. Applications which require different levels of, e.g., ionic conductivity, mechanical properties, and optical clarity, can take advantage of the quick and straight-forward membrane preparation process. It offers a platform to tailor membranes for different applications, including ion conductive membranes as well as other multifunctional materials.
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| 7. |
- Munch Elmér, Anette, et al.
(author)
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Polymer electrolyte membranes by in situ polymerization of poly(ethylene carbonate-co-ethylene oxide) macromonomers in blends with poly(vinylidene fluoride-co-hexafluoropropylene)
- 2007
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In: Journal of Polymer Science. Part B, Polymer Physics. - : Wiley. - 0887-6266 .- 1099-0488. ; 45:1, s. 79-90
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Journal article (peer-reviewed)abstract
- Salt-containing membranes based on polymethacrylates having poly(ethylene carbonate-co-ethylene oxide) side chains, as well as their blends with poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP), have been studied. Self-supportive ion conductive membranes were prepared by casting films of methacrylate functional poly(ethylene carbonate-co-ethylene oxide) macromonomers containing lithium bis(trifluorosulfonyl)imide (LiTFSI) salt, followed by irradiation with UV-light to polymerize the methacrylate units in situ. Homogenous electrolyte membranes based on the polymerized macromonomers showed a conductivity of 6.3 × 10-6 S cm-1 at 20 °C. The preparation of polymer blends, by the addition of PVDF-HFP to the electrolytes, was found to greatly improve the mechanical properties. However, the addition led to an increase of the glass transition temperature (Tg) of the ion conductive phase by 5 °C. The conductivity of the blend membranes was thus lower in relation to the corresponding homogeneous polymer electrolytes, and 2.5 × 10-6 S cm-1 was recorded for a membrane containing 10 wt % PVDF-HFP at 20 °C. Increasing the salt concentration in the blend membranes was found to increase the Tg of the ion conductive component and decrease the propensity for the crystallization of the PVDF-HFP component.
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| 8. |
- Munch Elmér, Anette, et al.
(author)
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Solid electrolyte membranes from semi-interpenetrating polymer networks of PEG-grafted polymethacrylates and poly(methyl methacrylate)
- 2006
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In: Solid State Ionics. - : Elsevier BV. - 0167-2738. ; 177:5-6, s. 573-579
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Journal article (peer-reviewed)abstract
- Solid polymer electrolyte membranes were prepared as semi-interpenetrating networks by photo-induced polymerization of mixtures of poly(ethylene glycol) (PEG) methacrylate macromonomers in the presence of poly(methyl methacrylate) (PMMA) and lithium bis(trifluoromethanesulfonyl)imide salt. The composition of the membranes was varied with respect to the PMMA content, the degree of cross-linking, and the salt concentration. Infrared analysis of the membranes indicated that the lithium ions were coordinated by the PEG side chains. Calorimetry results showed a single glass transition for the blend membranes. However, dynamic mechanical measurements, as well as a closer analysis of the calorimetry data, revealed that the blends were heterogeneous systems. The ionic conductivity of the membranes increased with the content of PEG-grafted polymethacrylate, and was found to exceed 10-5 S cm−1 at 30 °C for membranes containing more than 85 wt.% of this component in the polymer blend.
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| 9. |
- Munch Elmér, Anette, et al.
(author)
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Synthesis and characterization of poly(ethylene oxide-co-ethylene carbonate) macromonomers and their use in the preparation of crosslinked polymer electrolytes
- 2006
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In: Journal of Polymer Science. Part A, Polymer Chemistry. - : Wiley. - 0887-624X .- 1099-0518. ; 44:7, s. 2195-2205
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Journal article (peer-reviewed)abstract
- Methacrylate-functionalized poly(ethylene oxide-co-ethylene carbonate) macromonomers were prepared in two steps by the anionic ring-opening polymerization of ethylene carbonate at 180 °C, with potassium methoxide as the initiator, followed by the reaction of the terminal hydroxyl groups of the polymers with methacryloyl chloride. The molecular weight of the polymer went through a maximum after approximately 45 min of polymerization, and the content of ethylene carbonate units in the polymer decreased with the reaction time. A polymer having a number-average molecular weight of 2650 g mol-1 and an ethylene carbonate content of 28 mol % was selected and used to prepare a macromonomer, which was subsequently polymerized by UV irradiation in the presence of different concentrations of lithium bis(trifluoromethanesulfonyl)imide salt. The resulting self-supportive crosslinked polymer electrolyte membranes reached ionic conductivities of 6.3 × 10-6 S cm-1 at 20 °C. The coordination of the lithium ions by both the ether and carbonate oxygens in the polymer structure was indicated by Fourier transform infrared spectroscopy.
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