Topology and chemistry in the wetting of superhydrophobic surfaces in the presence of surfactants

COLL 21

Andrew J. B. Milne, ajmilne@ualberta.ca1, Karina Grundke, grundke@ipfdd.de2, Mirko Nitschke, nitschke@ipfdd.de2, Ralf Frenzel2, Frank Simon, frsimon@ipfdd.de2, and Alidad Amirfazli, a.amirfazli@ualberta.ca1. (1) Department of Mechanical Engineering, University of Alberta, Edmonton, AB T6G 2G8, Canada, (2) Polymer Interfaces, Leibniz Institute of Polymer Research Dresden, Hohe Strasse 6, Dresden, D-01069, Germany
The peculiar wetting behavior of anodically oxidized aluminum, plasma etched PTFE and cured Alkyl Ketene Dimer was investigated for surfactant solutions (sodium dodecyl sulphate, hexadecyltrimethylammonium bromide, n-decanoyl-n-methylglucamine) at three concentrations below Critical Micelle Concentration (CMC). Surface treatment (-CH3, -CF3) ensured chemically homogeneous superhydrophobic surfaces. Discussion focuses on the roles of topology and chemistry. Advancing contact angles for surfactants, measured using Axisymmetric Drop Shape Analysis, remained high (generally >140 degrees) at concentrations approaching the CMC while results for pure liquids with surface tensions similar to the surfactant solutions decreased (40-100 degrees lower, depending on chemistry and topology). Dual scale topology (aluminum) gave the highest contact angles for all liquids, with the dense spike pattern of PTFE in second. Modification with –CF3 gave higher, more stable contact angles. For maximum surfactant concentration, the receding angle decreases noticeably. It is hypothesized that a surfactant membrane forms over the surface pores, preventing liquid penetration.
 

Chemically and Topographically Textured Surfaces
8:30 AM-12:00 PM, Sunday, August 19, 2007 BCEC -- 153A, Oral

Division of Colloid & Surface Chemistry

The 234th ACS National Meeting, Boston, MA, August 19-23, 2007