In:
The Journal of Chemical Physics, AIP Publishing, Vol. 135, No. 24 ( 2011-12-28)
Abstract:
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 & gt; 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.
Type of Medium:
Online Resource
ISSN:
0021-9606
,
1089-7690
Language:
English
Publisher:
AIP Publishing
Publication Date:
2011
detail.hit.zdb_id:
3113-6
detail.hit.zdb_id:
1473050-9
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