Dynamic Properties of Self-Assembled Monolayers of Mercapto Oligo(ethylene oxide) Methyl Ether on an Oscillating Solid鈥揕iquid Interface

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• 作者：Minoru Yoshimoto ; Keita Honda ; Shigeru Kurosawa ; Mutsuo Tanaka
• 刊名：Journal of Physical Chemistry C
• 出版年：2014
• 出版时间：July 24, 2014
• 年：2014
• 卷：118
• 期：29
• 页码：16067-16073
• 全文大小：272K
• ISSN：1932-7455

文摘

The dynamic properties of chemisorbed soft matter on a solid鈥搇iquid interface oscillating at megahertz were investigated using a quartz crystal microbalance (QCM). As a chemisorbed soft matter, we employed the self-assembled monolayers of mercapto oligo(ethylene oxide) methyl ethers, HS(CH₂CH₂O)_nCH₃ (n = 5, 11, 12, 19, 27, 35, and 43), where those molecular weights had unity. The systematic analyses on the basis of the Voight model revealed that the molecular thickness moving with the solid鈥搇iquid interface oscillating at megahertz frequencies, the resonant length, is 8.8 nm, where the frequency dependence of the resonant length is not considered. On the other hand, the analyses based on the Debye process revealed that the logarithm of the resonant length linearly decreases with the logarithm of 2蟺F, where F is the frequency of the QCM, and varies from 17.3 (9 MHz) to 12.4 nm (81 MHz). Those values in the Debye process were within twice that of the Voight model and were approximately consistent with that in the Voight model. On the basis of the experimental data, we proposed the equation with the resonant length of HS(CH₂CH₂O)_nCH₃ as a function of frequency. Moreover, we discussed the difference between the chemisorbed and the physisorbed molecules on the solid鈥搇iquid interface oscillating at megahertz frequencies.