Dilational Viscosity of Langmuir monolayers
The dilational viscosity $ε'$ of Langmuir monolayer is considered in a theoretical model taking into account an orientational effect of the dilational wave on surface molecules. This orientational order is described by the surface order parameter Q; the orientational part of the free surface energy is given by Landau's expansion in powers of Q. The magnitude of surface viscosity, driven by the surface tension derivative $\partialγ/\partial Q$, is in good accord with the experimentally observed $ε'$. The sign of $ε'$ is positive that indicates that increased in-plane ordering increases the surface tension.
cond-mat.soft↗