Osada R, Hoshino T, Okada K, Ohmasa Y, Yao M
Department of Physics, Kyoto University, 606-8502 Kyoto, Japan.
J Chem Phys. 2009 May 14;130(18):184705. doi: 10.1063/1.3125182.
Using dynamic light scattering techniques, we obtained the surface tension sigma, surface excess entropy S(sigma), surface excess enthalpy H(sigma), and viscosity eta for the following seven room temperature ionic liquids in a wide temperature range from 30 to around 140 degrees C: 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, 1-hexyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, N-methyl-N-propylpiperidinium bis(trifluoromethanesulfonyl)imide, N,N,N-trimethyl-N-propylammonium bis(trifluoromethanesulfonyl)imide, 1-butyl-3-methylimidazolium hexafluorophosphate, 1-hexyl-3-methylimidazolium hexafluorophosphate, and 1-octyl-3-methyl imidazolium hexafluorophosphate. We have found that sigma increases systematically with decreasing the anion size and the alkyl side chain length. On the other hand, S(sigma) and eta increase with decreasing the anion size but decrease with decreasing the alkyl chain length. H(sigma) seems to decrease with increasing the anion size, but it has no clear dependence on the alkyl chain length. We discuss the bulk and surface properties, referring to the Coulomb interactions and van der Waals interactions.
使用动态光散射技术，我们在30至约140摄氏度的宽温度范围内，获得了以下七种室温离子液体的表面张力σ、表面过剩熵S(σ)、表面过剩焓H(σ)和粘度η：1-丁基-3-甲基咪唑双（三氟甲磺酰）亚胺、1-己基-3-甲基咪唑双（三氟甲磺酰）亚胺、N-甲基-N-丙基哌啶双（三氟甲磺酰）亚胺、N,N,N-三甲基-N-丙基铵双（三氟甲磺酰）亚胺、1-丁基-3-甲基咪唑六氟磷酸盐、1-己基-3-甲基咪唑六氟磷酸盐和1-辛基-3-甲基咪唑六氟磷酸盐。我们发现，σ随着阴离子尺寸和烷基侧链长度的减小而系统性增加。另一方面，S(σ)和η随着阴离子尺寸的减小而增加，但随着烷基链长度的减小而减小。H(σ)似乎随着阴离子尺寸的增加而减小，但它对烷基链长度没有明显的依赖性。我们参考库仑相互作用和范德华相互作用来讨论本体和表面性质。
