On the thermodynamics of solid solutions of polymer and salt

Winie

2017

Polymer International

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The sample preparation pathway of solid polymer electrolytes (SPEs) influences their thermal properties, which in turn governs the ionic conductivity of the materials especially for systems consisting of a crystallizable constituent. Majority of poly(ethylene oxide) (PEO)‐based SPEs with molar masses of PEO well above 104 g mol−1 (where PEO is crystallizable and should reach an asymptote in thermal behaviour) display molar mass dependence of the thermal properties and ionic conductivities in non‐equilibrium conditions, as reported in the literature. In this study, PEO of different viscosity‐molar masses (Mη = 3 × 105, 6 × 105, 1 × 106, 4 × 106 g mol−1) and LiClO4 salt (0 to 16.7 wt%) were used. The SPEs were thermally treated under inert atmosphere above the melting temperature of PEO and then cooled down for subsequent isothermal crystallization for sufficient experimental time to develop morphology close to equilibrium conditions. The thermal properties (e.g. glass transition temperature, melting temperature, crystallinity) according to differential scanning calorimetry and the ionic conductivity obtained from impedance spectroscopy at room temperature (σDC ∼ 10−6 S cm−1) demonstrate insignificant variation with respect to the molar mass of PEO at constant salt concentration. These findings are in agreement with the PEO crystalline structures using X‐ray diffraction and ion − dipole interaction by Fourier transform infrared results. © 2017 Society of Chemical Industry

Section: Resultssupporting

confidence: 94%

“… T g values of PEO 2 and PEO 4 against LiClO 4 mass fraction obtained from this study (dashed curve is for visual aid) and data from Chan et al …”

Section: Resultsmentioning

confidence: 78%

Section: Introductionmentioning

confidence: 99%

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Influence of molar mass on the thermal properties, conductivity and intermolecular interaction of poly(ethylene oxide) solid polymer electrolytes

Harun

Winie

2017

Polymer International

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“…Referring to our earlier work, the importance of thermal pre‐treatment on the samples comprising of semicrystalline polymer host (i.e. PEO) in order to obtain reproducible properties of SPEs which are independent of molar mass were highlighted.…”

Section: Introductionmentioning

confidence: 99%

Rheology and Microscopic Heterogeneity of Poly(ethylene oxide) Solid Polymer Electrolytes

Harun

Macromolecular Symposia

Guo

2017

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Lack of precise thermal control in poly(ethylene oxide) (PEO)‐based solid polymer electrolytes (SPEs) with molar masses well above M > 104 g mol−1 during preparatory stage often demonstrates molar mass dependence on thermal properties and ionic conductivities. In the earlier study, PEO‐based SPEs were heated under inert atmosphere above the melting temperature of PEO and then cooled down for subsequent isothermal crystallization. The system demonstrates insignificant variation with respect to molar mass of PEO at constant salt concentration for thermal properties, ionic conductivity and intermolecular interaction. Here, we report the subsequent results of rheology and microscopic heterogeneity as a function of PEO molar mass (Mɳ = 3 × 105 and 4 × 106 g mol−1) and lithium salt concentration (0–13 wt.%). Above the solubility limit of PEO, the glass transition studied using differential scanning calorimetry shows the presence of microscopic heterogeneity of the systems as indicated by the change in enthalpy of endothermic overshoot near the endset of glass transition. Rheological parameters were measured over a wide range of frequency (0.01 to 100 Hz) at different temperatures (30, 60 and 80 °C) using parallel plate geometry. Melt rheology system reveals that neat PEO at 80 °C exhibits restriction in the long‐range motion of the chains. When incorporated with salt, it exhibits further deviation from the terminal viscoelastic relaxation behaviour. This study agrees with our previous findings that influence of molar mass of PEO in this range is insignificant on the melt rheology and microscopic heterogeneity at constant salt concentration.

“…Ion conductivity (s DC ) of PEO SPEs is mainly ruled by the ion mobility and ion concentration in the amorphous phase of these systems. [6][7][8][9] PEO consists of $ 60% of crystalline phase at room temperature. [10] Thus, PEO-based SPEs suffer low conductivity ($ 10…”

Section: Introductionmentioning

confidence: 99%

On Thermal and Spectroscopic Studies of Poly(ethylene oxide)/Poly(methyl methacrylate) Blends with Lithium Perchlorate

Karim

Sim

Macromolecular Symposia

et al. 2015

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Summary: In this study, thermal properties and ion-polymer interactions of lithium perchlorate (LiClO 4 ) in poly(ethylene oxide)/poly(methyl methacrylate) (PEO/PMMA) blend prepared by solution casting technique were elucidated. The spectroscopic studies of the salt-free and salt-doped PEO/PMMA blends were investigated using x-ray diffraction (XRD) and Fourier transform infra-red (FTIR), respectively. XRD study reveals that the crystalline structure of PEO is slight change when PMMA is blended to PEO. The thermal behaviour of PEO, PMMA and their blends with and without LiClO 4 was investigated by differential scanning calorimetry (DSC). The presence of a single and composition dependent glass transition temperature (T g ) reflects the miscibility of the salt-free PEO/PMMA blends in the molten state. The T g s of PEO, PMMA and the blends generally increase with ascending mass fraction of salt (W S ). However, PEO/PMMA 50/50 blend with W S ! 0.091 shows phase separation between the two polymers. The melting temperature (T m ) and crystallinity (X Ã ) of PEO are suppressed when blended with PMMA, thus, confirm the miscibility of the salt-free PEO/PMMA blends in the molten state. Presence of LiClO 4 to PEO, PMMA and their blends does not influences the X Ã of PEO. Investigation by FTIR does not show any specific interaction between PEO and PMMA for the salt-free blends whereas for the salt-doped blends, Li þ ions are observed to coordinate with the oxygen atom of both the PEO ether and the PMMA carboxyl groups. Impedance spectroscopy study demonstrates that the LiClO 4 -doped PEO/PMMA 75/25 blend has lower ion conductivity than that of the PEO þ LiClO 4 system but recorded enhanced conductivity as compared to PMMA þ LiClO 4 systems at W S ¼ 0.091.