The kinetics of dewetting of hydrophobic surfaces during the evaporation of surfactant solution drops

Abstract

The kinetics of dewetting (a decrease in contact angles and wetted surface area) during the evaporation of drops of cetyltrimethylammonium bromide (CTAB) solutions from paraffin and Teflon surfaces was studied in a wide concentration range. Three different stages of this process were found: (1) a monotonic decrease in the contact angle at a “fixed” position of the three-phase contact line, (2) contraction of the wetted surface area (the drop base) at a constant contact angle, and (3) simultaneous contraction of the drop base and a decrease in the contact angle. The CTAB distribution over a solid surface after the drop evaporation was studied by autoradiography. Depending on the surfactant concentration and the nature of a hydrophobic substrate, dewetting occurs by two mechanisms: slipping and “carpet rolling.”