IV-SFGおよびMAESによるイオン液体の表面構造観察

抄録

The air/liquid interface of room temperature ionic liquids with 1-alkyl-3-methylimidazolium cations was studied using infrared-visible sum frequency generation (IV-SFG) vibrational spectroscopy and metastable atom electron spectroscopy (MAES). The air/liquid interface is covered with equally anions and cations if the alkyl chain is rather short, but longer alkyl chains tend to shield the anions. The probability of the gauche defect per CH₂-CH₂ bond in the alkyl chain decreases as the number of carbon atoms in the alkyl chain increases. This finding suggests that the interaction between the alkyl chains is enhanced as the alkyl chain length becomes longer. A local structure, which originates from the intermolecular interaction between the ionic liquid molecules, is proposed to explain these observations.