Monolayer spreading of polydimethylsiloxane oil on surfactant solutions

The radial spreading rate of polydimethylsiloxane oil monolayers on various surfactant solutions is measured by observing Teflon tracer particles with a video microscope. We find that a simple model, based solely on Marangoni driven surface tension gradients, accurately predicts the power-law behavior observed for these expanding monolayers. In addition, we document observations of so-called pseudopartial wetting, and discuss its connection to more classical wetting theories.