Time-dependent Dynamic Receding Contact Angles Studied during the Flow of Dilute Aqueous Surfactant Solutions through Fluorinated Microtubes

We report on the time-dependent dewetting behavior of dilute surfactant solutions of hexadecyltrimethylammonium bromide (CTAB) during forced flow in fluorinated ethylene­ propylene (FEP) microtubes. The dynamic receding contact angle of the solution at a given velocity decreased as the solid­ liquid contact time increased. Kinetics with long relaxation time of several hundred seconds led to a final state displaying a 0° dynamic receding contact angle. This effect was absent in the case of 2-propanol, where the dynamic receding contact angle did not depend on the contact time.