Shear response of polyelectrolytes in water.

Abstract

The shear response of polyelectrolytes in solutions drives distinct microscopic conformational dynamics whose correlation with macroscopic rheological properties remains an open question. Using large-scale, fully atomistic molecular dynamics simulations of aqueous solutions of fully sulfonated polystyrene polyelectrolytes, we probe their conformational dynamics under shear. In contrast to their quiescent extended configuration, we find that the chains exhibit a wide variety of conformational fluctuations, folding back with minimal extension in the transverse direction, often resulting in tumbling at a characteristic time τ_{r} that scales with the shear rate as γ[over ̇]^{-2/3}. These results, together with similar scaling previously observed experimentally for biomolecules, have established that tumbling dynamics transcends many orders of magnitude in shear rate.