Emerging slow dynamics of collapsed polymers flowing through porous media

Using hydrodynamic simulations, we examine the behavior of single polymers flowing through model three-dimensional porous media (face-centered cubic close-packed colloidal crystal), where we observed that solvent properties and flow rates play an import role for polymer transport. In good solvent or high flow rates, the transport dynamics are similar to DNA gel electrophoresis, that is, the polymers showed size dependent Ogston sieving velocity for L_c/L < ~1 and size independent biased reptation velocity for L_c/L > ~1 (here L_c is the polymer contour length and L is the diameter of colloids that forms the porous media). Importantly, in bad solvent and low flow rates, the polymers showed an extra window of size dependent velocity for ~1 < L_c/L < ~2, which, to the best of our knowledge, has not been reported. In this regime, the polymer transport is controlled by a globule-stretch transition at pore throats, and the transport velocity is much slower than reptation. These findings are important for understanding the mechanical entrapment when using polymers for subsurface applications such as polymer flooding, and to design new ways for the separation of (bio)macromolecules.