Effect of the Reorientation of Oxyethylated Alcohol Molecules within the Surface Layer on Equilibrium and Dynamic Surface Pressure

The diffusion-controlled adsorption kinetics of surfactant molecules at liquid interface is solved considering an additional rate constant for reorientation processes taking part within the surface layer. It is shown that a noninstantaneous reorientation can result in either acceleration or deceleration of surface tension changes as compared to a simple Langmuir model. The measured dynamic and equilibrium surface (interfacial) tensions for C 10 EO 8 at the water/air and water/hexane interfaces agree well with the presented model derived for molecules which can exist in two (or more) orientation states. At low and medium surface pressures the reorientation model describes the experimental data well and predicts a more rapid decrease of surface tension as compared with the Langmuir model.