Thermodynamics and Phase Behavior of Poly(ethylene oxide)/Poly(methyl methacrylate)/Salt Blend Electrolytes Studied by Small-Angle Neutron Scattering

Neel J. Shah; Lilin He; Kevin W. Gao; Nitash P. Balsara

doi:10.1021/acs.macromol.2c02533

Thermodynamics and Phase Behavior of Poly(ethylene oxide)/Poly(methyl methacrylate)/Salt Blend Electrolytes Studied by Small-Angle Neutron Scattering

Neel J. Shah, Lilin He, Kevin W. Gao, Nitash P. Balsara

SANS & Spin Echo

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6 Scopus citations

Abstract

We studied the effect of added salt on the thermodynamics of a miscible polymer blend system: poly(ethylene oxide) (PEO) blended with poly(methyl methacrylate) (PMMA). In the absence of salt, PEO/PMMA blends are known to exhibit a negative Flory-Huggins parameter, χ. Not surprisingly, the salt-free PEO/PMMA blends are miscible, regardless of composition. The addition of salt, which in our case was lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), induced phase separation in majority-PMMA blends, while majority-PEO blends remained miscible. The effect of added salt was studied at two salt concentrations, r = 0.05 and r = 0.10; r is defined as the molar ratio of lithium ions to ether oxygens (r = [Li]/[EO]). The immiscibility window, which was absent at r = 0, grew upon addition of a small amount of salt (r = 0.05). Further addition of salt to r = 0.10 results in shrinking of the immiscibility window. With small-angle neutron scattering (SANS) profiles from homogeneous blends, we determined χ in both the presence and absence of salt. We measure the composition dependence of this parameter and use it to predict the phase behavior of PEO/PMMA/LiTFSI blends. We find good agreement between theory and experiment.

Original language	English
Pages (from-to)	2889-2898
Number of pages	10
Journal	Macromolecules
Volume	56
Issue number	7
DOIs	https://doi.org/10.1021/acs.macromol.2c02533
State	Published - Apr 11 2023

Funding

This work was supported by the Joint Center for Energy Storage Research (JCESR), an Energy Innovation Hub funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Science, under Contract No. DE-AC02-06CH11357. Partial support for N.J.S. was provided by the National Science Foundation grant DMR 1904508 to the University of California, Berkeley. K.W.G. acknowledges funding from a National Defense and Science Engineering Graduate Fellowship. This research used resources at the High Flux Isotope Reactor, a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory.

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title = "Thermodynamics and Phase Behavior of Poly(ethylene oxide)/Poly(methyl methacrylate)/Salt Blend Electrolytes Studied by Small-Angle Neutron Scattering",

abstract = "We studied the effect of added salt on the thermodynamics of a miscible polymer blend system: poly(ethylene oxide) (PEO) blended with poly(methyl methacrylate) (PMMA). In the absence of salt, PEO/PMMA blends are known to exhibit a negative Flory-Huggins parameter, χ. Not surprisingly, the salt-free PEO/PMMA blends are miscible, regardless of composition. The addition of salt, which in our case was lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), induced phase separation in majority-PMMA blends, while majority-PEO blends remained miscible. The effect of added salt was studied at two salt concentrations, r = 0.05 and r = 0.10; r is defined as the molar ratio of lithium ions to ether oxygens (r = [Li]/[EO]). The immiscibility window, which was absent at r = 0, grew upon addition of a small amount of salt (r = 0.05). Further addition of salt to r = 0.10 results in shrinking of the immiscibility window. With small-angle neutron scattering (SANS) profiles from homogeneous blends, we determined χ in both the presence and absence of salt. We measure the composition dependence of this parameter and use it to predict the phase behavior of PEO/PMMA/LiTFSI blends. We find good agreement between theory and experiment.",

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AU - Balsara, Nitash P.

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N2 - We studied the effect of added salt on the thermodynamics of a miscible polymer blend system: poly(ethylene oxide) (PEO) blended with poly(methyl methacrylate) (PMMA). In the absence of salt, PEO/PMMA blends are known to exhibit a negative Flory-Huggins parameter, χ. Not surprisingly, the salt-free PEO/PMMA blends are miscible, regardless of composition. The addition of salt, which in our case was lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), induced phase separation in majority-PMMA blends, while majority-PEO blends remained miscible. The effect of added salt was studied at two salt concentrations, r = 0.05 and r = 0.10; r is defined as the molar ratio of lithium ions to ether oxygens (r = [Li]/[EO]). The immiscibility window, which was absent at r = 0, grew upon addition of a small amount of salt (r = 0.05). Further addition of salt to r = 0.10 results in shrinking of the immiscibility window. With small-angle neutron scattering (SANS) profiles from homogeneous blends, we determined χ in both the presence and absence of salt. We measure the composition dependence of this parameter and use it to predict the phase behavior of PEO/PMMA/LiTFSI blends. We find good agreement between theory and experiment.

AB - We studied the effect of added salt on the thermodynamics of a miscible polymer blend system: poly(ethylene oxide) (PEO) blended with poly(methyl methacrylate) (PMMA). In the absence of salt, PEO/PMMA blends are known to exhibit a negative Flory-Huggins parameter, χ. Not surprisingly, the salt-free PEO/PMMA blends are miscible, regardless of composition. The addition of salt, which in our case was lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), induced phase separation in majority-PMMA blends, while majority-PEO blends remained miscible. The effect of added salt was studied at two salt concentrations, r = 0.05 and r = 0.10; r is defined as the molar ratio of lithium ions to ether oxygens (r = [Li]/[EO]). The immiscibility window, which was absent at r = 0, grew upon addition of a small amount of salt (r = 0.05). Further addition of salt to r = 0.10 results in shrinking of the immiscibility window. With small-angle neutron scattering (SANS) profiles from homogeneous blends, we determined χ in both the presence and absence of salt. We measure the composition dependence of this parameter and use it to predict the phase behavior of PEO/PMMA/LiTFSI blends. We find good agreement between theory and experiment.

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Thermodynamics and Phase Behavior of Poly(ethylene oxide)/Poly(methyl methacrylate)/Salt Blend Electrolytes Studied by Small-Angle Neutron Scattering

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