Experimental evidences for molecular origin of low-<i>Q</i> peak in neutron/x-ray scattering of 1-alkyl-3-methylimidazolium bis(trifluoromethanesulfonyl)amide ionic liquids
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- Kenta Fujii
- The University of Tokyo 1 Neutron Scattering Laboratory, Institute for Solid State Physics, , Kashiwa, Chiba 277-8581, Japan
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- Ryo Kanzaki
- Kagoshima University 2 Graduate School of Science and Engineering, , Korimoto, Kagoshima 890-0065, Japan
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- Toshiyuki Takamuku
- Saga University 3 Department of Chemistry and Applied Chemistry, Graduate School of Science and Engineering, , Honjo-machi, Saga 840-8502, Japan
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- Yasuo Kameda
- Yamagata University 4 Department of Material and Biolgical Chemistry, Faculty of Science, , 1-4-12 Kojirakawa-machi, Yamagata 990-8560, Japan
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- Shinji Kohara
- Japan Synchrotron Radiation Research Institute (JASRI) 5 , Sayo-cho, Sayo-gun, Hyogo 679-5198, Japan
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- Mitsuhiro Kanakubo
- National Institute of Advanced Industrial Science and Technology (AIST) 6 , 4-2-1, Nigatake, Miyagino-ku, Sendai 983-8511, Japan
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- Mitsuhiro Shibayama
- The University of Tokyo 1 Neutron Scattering Laboratory, Institute for Solid State Physics, , Kashiwa, Chiba 277-8581, Japan
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- Shin-ichi Ishiguro
- Kyushu University 7 Department of Chemistry, Faculty of Science, , Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan
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- Yasuhiro Umebayashi
- Kyushu University 7 Department of Chemistry, Faculty of Science, , Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan
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説明
<jats:p>Short- and long-range liquid structures of [CnmIm+][TFSA−] with n = 2, 4, 6, 8, 10, and 12 have been studied by high-energy x-ray diffraction (HEXRD) and small-angle neutron scattering (SANS) experiments with the aid of MD simulations. Observed x-ray structure factor, S(Q), for the ionic liquids with the alkyl-chain length n > 6 exhibited a characteristic peak in the low-Q range of 0.2–0.4 Å −1, indicating the heterogeneity of their ionic liquids. SANS profiles IH(Q) and ID(Q) for the normal and the alkyl group deuterated ionic liquids, respectively, showed significant peaks for n = 10 and 12 without no form factor component for large spherical or spheroidal aggregates like micelles in solution. The peaks for n = 10 and 12 evidently disappeared in the difference SANS profiles ΔI(Q) [=ID(Q) − IH(Q)], although that for n = 12 slightly remained. This suggests that the long-range correlations originated from the alkyl groups hardly contribute to the low-Q peak intensity in SANS. To reveal molecular origin of the low-Q peak, we introduce here a new function; x-ray structure factor intensity at a given Q as a function of r, SQpeak(r). The SQpeak(r) function suggests that the observed low-Q peak intensity depending on n is originated from liquid structures at two r-region of 5–8 and 8–15 Å for all ionic liquids examined except for n = 12. Atomistic MD simulations are consistent with the HEXRD and SANS experiments, and then we discussed the relationship between both variations of low-Q peak and real-space structure with lengthening the alkyl group of the CnmIm.</jats:p>
収録刊行物
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- The Journal of Chemical Physics
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The Journal of Chemical Physics 135 (24), 244502-, 2011-12-27
AIP Publishing