Self-Assembled Monolayers of Alkanethiols on Gold: Monolayers Derived From Two Components with Alkane Chains of Different Lengths

Abstract : This paper describes the preparation and wetting properties of two-component self-assembled monolayers (SAMs) obtained by the competitive adsorption of one short-chain (HS(CH2)1OSh) and one long-chain (HS(CH2)21LG) alkanethiol onto gold from dilute ethanolic solutions. The four possible combinations of the tail groups CH3 and CH20H were investigated: Sh = CH3/Lg = CH20H, Sh = CH2OH/Lg = CH3, SH = CH2OH/Lg = CH2OH, and Sh = CH3/Lg = CH3. The compositions of these SAMs are not the same as the compositions of the solutions from which they were formed, and the relationship between these compositions suggests that the SAMs have partially phase separated. Contact angles with water and hexadecane, however, show that significant disorder still remains in the interfacial region.