Tuning Surface Wettability of Poly(3-sulfopropyl methacrylate) Brushes by Cationic Surfactant-Driven Interactions

In this communication, polyanionic poly(potassium 3-sulfopropyl methacrylate) (PSPM) brushes were switched from hydrophilic to hydrophobic by exchange of the counter cations. First, poly(potassium 3-sulfopropyl methacrylate) brushes were grown by means of atom transfer radical polymerization (ATRP) from thiol monolayers of initiating -mercaptoundecyl bromoisobutyrate and mixed monolayers of thiol initiator and 1-undecanothiol (blank thiol) attached to gold surfaces. The kinetics of the polymerization reaction were followed by means of the quartz microbalance technique with dissipation (QCM-D). The collapse of PSPM brushes in the presence of cationic surfactants like quaternary ammonium salts (tetraethylammonium bromide, hexadecyltrimethylammonium bromide) and imidazolium salts (1-dodecyl-3-methylimidazolium bromide, 1H,1H,2H,2H-perfluoro-1-decyl-3-methylimidazolium bromide) was shown by QCM-D. Water contact angle measurements proved that the wettability of the surface could be tuned reversibly from hydrophilic values (<30 °) to hydrophobic ones (>85 °).