Web Release Date: January 3,
Use of Alkane Monolayer Templates To Modify the Structure of Alkyl Ether Monolayers on Highly Ordered Pyrolytic Graphite
Beckman Institute and Kavli Nanoscience Institute, Division of Chemistry and Chemical Engineering, 210 Noyes Laboratory, 127-72, California Institute of Technology, Pasadena, California 91125
Received August 21, 2007
In Final Form: September 20, 2007
Abstract:
Scanning tunneling microscopy (STM) has been used to investigate the structure of pure and mixed monolayers
formed by adsorption of long-chain alkanes and/or ethers on highly ordered pyrolytic graphite. Application of a pure
phenyloctane solution of simple alkanes, such as tritriacontane, CH3(CH2)31CH3, produced a monolayer within which
the individual molecular axes were oriented perpendicular to the lamellar axes. In contrast, a pure solution of symmetrical
long-chain ethers, such as di-n-hexadecyl ether, CH3(CH2)15O(CH2)15CH3, produced a monolayer within which the
molecular axes were oriented at an angle of 
65
relative to the lamellar axes. The compositions of the overlying
solutions were then gradually changed either from pure alkanes to nearly pure ethers or from pure ethers to nearly
pure alkanes. When ethers replaced alkanes in the monolayer, the ethers conformed to the orientation within the
existing alkane layer, rather than adopting the characteristic orientation of pure ether monolayers. However, when
alkanes were incorporated into monolayers that had been formed from pure ether solutions, the orientation of the
molecules within the monolayer converted to that characteristic of pure alkanes. Alkane monolayers thus acted as
templates for subsequent ether layers, but ether monolayers did not act as templates for alkane layers.
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