Tunable Hydrophobicity via Dimensionally Confined Polymerization of Organometallic Adducts

Role of Nanoscale Roughness and Polarity in Odd-Even Effect of Self-Assembled Monolayers

The dependency of substrate roughness on wetting properties of self-assembled monolayers (SAMs) has been studied extensively, but most previous studies used limited selection of probing liquid and range of surface roughness. These studies disregarded the limit to observation of sub-nanometer odd-even parity effect, hence are inconclusive. In this work we report the role of solvent polarity on the roughness-dependency of wetting behavior of SAMs by studying static con-tact angle of a variety of probing liquids, with different polarities, on SAMs formed on Ag-based substrate with different surface morphology. By overlapping the roughness ranges with previous studies on Au, the limitation of surface roughness (RMS=1 nm) to observation of the odd-even effect using water as probing liquid was confirmed, but other probing liquid yielded different roughness-dependent behaviors, with more polar solvent showing more roughness-dependent behavior. Based on these observations, we concluded that there exists a phase-transition like behavior in SAMs due to substrate roughness and molecule chain length, but whose determination is dependent on the probing liquid.

Tunable Hydrophobicity via Dimensionally Confined Polymerization of Organometallic Adducts

Fabrication of tunable fine textures on solid metal surfaces often demands sophisticated reaction/processing systems. By exploiting in situ polymerization and self-assembly of inorganic adducts derived from liquid metals (the so-called HetMet reaction) with concomitant solidification, solid metal films with tunable texture are readily fabricated. Serving as a natural dimensional confinement, interparticle pores and capillary-adhered thin liquid films in a pre-packed bed of undercooled liquid metal particles lead to the expeditious surface accumulation of organometallic synthons, which readily oligomerize and self-assemble into concentration-dictated morphologies/patterns. Tuning particle size, particle packing (flat or textured), and reactant concentration generates diverse, autonomously organized organometallic structures on a metal particle bed. Concomitant solidification and sintering of the underlying undercooled particle bed led to a multiscale patterned solid metal surface. The process is illustrated by creating tunable features on pre-organized metal particle beds with concomitant tunable wettability as illustrated through the so-called petal and lotus effects.