Control of surface properties of self-assembled monolayers by tuning the degree of molecular asymmetry

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• 作者：Susana Moreno Flores ; Andrey Shaporenko ; Chandrasekhar Vavilala ; Hans-Jü ; rgen Butt ; Michael Schmittel ; Michael Zharnikov and Rü ; diger Berger
• 关键词：Self-assembly ; Asymmetric dialkyldisulfide derivatives ; Scanning probe techniques ; Chemical force microscopy ; Wetting ; X-ray photoelectron spectroscopy ; Infrared reflection absorption spectroscopy
• 刊名：Surface Science
• 出版年：2006
• 出版时间：15 July 2006
• 年：2006
• 卷：600
• 期：14
• 页码：2847-2856
• 全文大小：349 K

文摘

We have studied self-assembled monolayers (SAMs) of asymmetric dialkyldisulfide derivatives of the form CH₃–(CH₂)_11+m–S–S–(CH₂)₁₁–OH with m = −4, −3, 0, +2 and +4 on gold. Sub-nanoscale changes in the length of the CH₃-terminated alkylchain have been used to selectively protrude one particular end group in the resulting film. The alteration of the chain length in only two methylene units already results in changes of surface properties, which have been detected with local (chemical force microscopy) and macroscopic (contact angle) techniques. In particular, advancing contact angles can be adjusted between 40° and 80°. The adhesion between a hydrophobic tip and these SAMs in water is determined by the chemical nature of the protruding end group. Chemical force microscopy, X-ray photoelectron spectroscopy and infrared reflection absorption spectroscopy have shown that these SAMs are composed of mixed, well-packed CH₃– and OH–alkylthiolate branches. The surface composition ratio is close to 1:1 for all investigated SAMs.