Scaling of dynamics in 2d semi-dilute polymer solutions

We study the viscoelasticity of surface polymer monolayers by measuring the dynamics of thermal concentration fluctuations with surface light scattering. For various systems of proteins and synthetic polymers we find a semi-dilute regime in which both the elastic and viscous components of the dilational modulus show power law dependencies on the concentration. Surprisingly there is a universal relationship between the exponents for the two components: the viscosity scales with a power double that of the elasticity. These results cannot be explained on the basis of theory developed for bulk systems, and a simple explanation for the singular 2d behavior is suggested.