Rhamnolipid biosurfactant behavior in solutions

The solution behavior of rhamnolipid biosurfactant that is determined by its surface thermodynamic properties often plays a central role in determining and controlling its performance in practical applications. In this study, rhamnolipid molecules exhibited a predominant hydrophilic surface, contributed by hydrophilic monomer head groups. Interaction free energies between rhamnolipid molecules at water surfaces, as estimated based on the distance-dependent decaying interaction contact areas, decayed exponentially with regards to separation distance. These interaction free energies were governed by hydrophilic monomer head groups of rhamnolipid molecules. The experimental observations in this study were consistent with the previous postulations.