Homogeneously and gradually anchored self-assembled monolayer by tunable vapor phase-assisted silanization

Abstract

A versatile and straightforward grafting approach in the vapor phase was developed in view of preparing alkyl self-assembled monolayers uniformly or gradually anchored onto silica surfaces, as demonstrated by wettability and XPS measurements. The understanding of the mechanism which dictates the grafting in the vapor phase was investigated through changing the experimental parameters. The control of the propagating front diffusion consisting of silane vapor afforded a concentration gradient, leading to a gradual grafting with features such as hydrophobicity steepness and spatial amplitude which can be tuned by changing the time and/or temperature of exposure. This results in changes to the concentration and diffusion of the vaporized silane molecules as well as changing the silane–substrate’s interfacial chemical reactivity. Such single-component gradient surfaces were utilized as molecular (nano)templates to generate a heterogeneous two-component gradient by simply performing a backfilling with fluorine or amine-functionalized silane derivatives.