Superhydrophobic self-assembled monolayers of long-chain fluorinated imidazolium ionic liquids

Abstract

Self-assembled monolayers (SAMs) of 1-long-chain fluorinated-alkyl-3-(3-triethoxysilylpropyl)-4,5-dihydroimidazolium ionic liquids (C_nFtespim⁺X⁻) were fabricated via –Si–O– covalent bonds on Al substrates and the wettability of Al substrates with SAMs was studied. The water contact angles (CAs) of Al substrates coating with SAMs increase with the increase of the chain length of C_nFtespim⁺X⁻ and X⁻ can be tuned by the exchange of counteranions. It was found that the effect of counteranions on the wettability of SAMs was dependent on the cations in some degree. Combining with micro- and nano-scale hierarchical structures via being treated with 4 mol L⁻¹ HCl aqueous solution for 12.5 min, superhydrophobic Al surfaces having CA above 160° at n ≥ 6 can be obtained. The unique chemical and thermal stabilities of ionic liquids could be transferred to the Al substrate surfaces through anchoring, which should satisfy the superhydrophobic requirements of especial environments.