Designing Surfaces with Wettability That Varies in Response to Solute Identity and Concentration

Surfaces with solute responsive wettability can be prepared by covalent layer-by-layer assembly of PNIPAM-c-PNASI with 10 and 100 nm diameter aminated silica nanoparticles. These surfaces are found to exhibit reversible changes in surface wetting in response to solute anion identity and concentration, allowing surfaces to be switched from hydrophilic (advancing water contact angle 68 degrees) to hydrophobic (advancing water contact angle 145 degrees). The extent of the response to solute salts is found to be consistent with the Hofmeister series and with associated changes in surface roughness which result from varying degrees of polymer swelling in response to solute ion identity and concentration. The observed wettability changes on these surfaces are reversible.