The Interfacial Physics Group

Carnegie Mellon University, Department of Physics

Marangoni Driven Flow of Surfactant Solutions on Polymer Solution Subphase by Chiung-Hsuan Chung




The main objective of this thesis is to find out the short term spreading behavior of surfactant solutions spreading on a polymeric solution subphase.  Two different experiments were done simultaneously to investigate the research.  Spreading experiments were done to quantify the motion of the surfactant solution.  Surface tension measurements were made to determine the surface tension difference between the subphase and the initial condition of the surfactant solution. 
      The major findings of this thesis are: 1.) The initial spreading rate varies monotonically with surface tension difference.  If the difference is negative the spreading will not begin.  2.) The spreading behavior has two different regimes, above and below CMC.  3.) The end of the spreading event cannot be accounted for by all surfactant staying on the surface of the subphase and the surface tension becoming uniform across the entire subphase surface.  Other preliminary work is also reported here: 1.) a study of the appearance of an apparent instability during spreading; 2.) an examination of the time scale for mixing of the surfactant solution with the polyacrylamide subphase; 3.) a comparison of spreading behavior on simple and complex fluid subphases; and 4.) a measurement of time of the onset of movement of surface tracer particles and its correspondence to the speed of the shock wave moving across the surface.