The effect of the surfactant chain length $n$ on the bending modulus $\kappa$ of surfactant monolayers is simulated with a mesoscopic oil-water-surfactant model. We confirm a power law, $\kappa \propto n^p$, as predicted by mean-field theory and found experimentally, and find $p\approx 1.5$ at a constant surface density and $p\approx 1.0$ at a constant interfacial tension. This agrees quite well with both mean-field theory ($p=2–3$, assuming constant surface density) and experiments (at constant surface tension). Our results suggest that the previously reported agreement between theory and experiment may be fortuitous and caused by the difference in surfactant types.

• Received 22 October 2003

DOI:https://doi.org/10.1103/PhysRevLett.92.116101