Formation and Reaction of Interchain Carboxylic Anhydride Groups on Self-Assembled Monolayers on Gold

This paper demonstrates a new method for the synthesis of mixed self-assembled monolayers (mixed SAMs) by reaction of a reactive intermediatean interchain carboxylic anhydridewith alkylamines. The interchain anhydride was prepared in high yield from a SAM of 16-mercaptohexadecanoic acid (HS(CH2)15COOH) on gold by treatment with trifluoroacetic anhydride. Alkylamines reacted cleanly with the interchain anhydride to generate a mixed SAM, which comprised a mixture of acids and amides in approximately 1:1 ratio on the surface. The SAMs of the interchain anhydride and the mixed SAM were characterized using polarized infrared external reflectance spectroscopy, X-ray photoelectron spectroscopy, contact angle, and ellipsometry. Control of the wettability of the SAMs was demonstrated by allowing the interchain anhydride to react with alkylamines having different alkyl groups; this model system gave wetting data consistent with earlier studies of mixed monolayers and verified the ability of this method to manipulat...