Molecular Dynamics Simulation of Oxygen Transport through ω-Alkoxy-n-alkanethiolate Self-Assembled Monolayers on Gold and Copper

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• 作者：Piyush Srivastava^† ; ; Walter G. Chapman*^† ; ; Paul E. Laibinis*^† ; ^‡ ;
• 刊名：Langmuir
• 出版年：2009
• 出版时间：March 3, 2009
• 年：2009
• 卷：25
• 期：5
• 页码：2689-2695
• 全文大小：252K
• 年卷期：v.25,no.5(March 3, 2009)
• ISSN：1520-5827

文摘

We have used molecular dynamics (MD) simulations to investigate the influences of the position of the ethereal oxygen on the ability of ω-alkoxy-n-alkanethiolate self-assembled monolayers (SAMs) to act as barrier films against through-film oxygen transport as relevant to the uses of these films in corrosion inhibition. Our MD simulations reveal that when the ether linkage is too close to the metal surface or to the chain ends, the free-energy barrier of SAMs toward oxygen diffusion was 5 kJ/mol less than for a non-ether-containing n-alkanethiolate SAM having the same chain length. MD simulations show that SAMs having an ether linkage near a chain end contain a highly disordered terminal region. As a result, the SAMs allow a more rapid transport of oxygen across these monolayers than through n-alkanethiolate SAMs of similar length lacking the ether unit. Additionally, SAMs with the ether linkage close to the metal surface undergo a structural transition to an alternating flipped structure that is less crystalline compared to that of an n-alkanethiolate SAM. Together, these factors diminish the barrier properties of the ω-alkoxy-n-alkanethiolate SAMs below those for their unsubstituted analogues.