Preparation of Self-Assembled Thiol Monolayer Coated Copper Surfaces with Wettability Gradient

Abstract

A new method has been developed to prepare copper plates with a wettability gradient by means of electrochemical reduction and coating of the resulting surfaces with thiol self-assembled monolayers (SAMs). The wettability of the surfaces could be easily modified by varying the surface roughness according to degree of electrochemical reduction and by changing the type of thiol coating. Thiol SAM-coated copper surfaces with wettability gradient could be generated by painting the ethanolic solutions of hydrophobic perfluoroalkylthiols and hydrophilic mercaptoalcohols on the surface of the electrochemically reduced oxide-free cupper electrodes of varying roughness. The results of a simple vapor condensation test for the modified surfaces showed that numerous liquid droplets nucleate and grow by coalescence with surrounding drops, then the droplets rapidly move from the perfluoroalkylthiol SAM-covered hydrophobic side to the mercaptoalcohol SAM-covered hydrophilic side. This phenomenon could be useful for passively enhancing heat transfer including two-phase change in heat exchangers and heat pipes.