Nanostructure,interactions, and conductivities of polymer electrolytes comprising silver salt and microphase‐separated graft copolymer |
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| Authors: | Do Kyoung Lee Kyung Ju Lee Yong Woo Kim Byoung Ryul Min Jong Hak Kim |
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| Institution: | 1. Department of Chemical Engineering, Yonsei University, Seodaemun‐gu, Seoul 120‐749, South Korea;2. Department of Chemical Engineering, Yonsei University, Seodaemun‐gu, Seoul 120‐749, South KoreaDepartment of Chemical Engineering, Yonsei University, Seodaemun‐gu, Seoul 120‐749, South Korea |
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| Abstract: | 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 Tg 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 |
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| Keywords: | silver polymer electrolyte graft copolymer conductivity interaction |
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