Synthesis of thiol-functionalized ionic liquids and formation of self-assembled monolayer on gold surfaces: Effects of alkyl group and anion on the surface wettability

Twenty four thiol-functionalized ionic liquids based on imidazolium cation, 1-(12-mercaptododecyl)-3-alkylimidazolium salts, have been synthesized, and utilized to investigate the effects of alkyl-chain length and anion on the wettability of Au surfaces on the basis of self-assembled monolayers presenting [(CnSAMIM)X], where n = 1-6,X = Br, BF₄, PF₄ and NTf ₂. Water wettabilities of the surfaces were measured as a water contact angle by contact angle goniometry. It was found that water wettability of the Au surfaces coated with imidazolium ions was largely dependent not only on counter anions but also on the length of alkyl chains. In the case of SAMs of N-alkylimidazolium ions having short length of N-alkyl chain (C ₁-C₄), anions played great role in determining water wettability of the surfaces.