Conformational dynamics of submicron-sized wormlike polyelectrolyte chain in viscous fluid flows

Abstract

Polyelectrolytes are distinguished from neutral polymers, due to the long-range interactions resulting from charged chains and mobile counterions. We investigated the single chain of polyelectrolyte in the external flow fields by extending our previous studies on coarse-grained Brownian dynamics simulation. Submicron-sized xanthan biopolymer was chosen as a model polyelectrolyte that includes the hydrodynamic interaction and the electrostatic screening effect taking into account wormlike chains. Conformational properties, such as radius of gyration and static structure factor, are unchanged with the flow strength (i.e., Weissenberg number) in the uniform flow. In contrast, influences by flow strength as well as flow type become evident in both simple shear and extensional-like flows with non-zero velocity gradients in flow regimes, commonly representing a sigmoidal transition in the radius of gyration. Transition to a higher plateau can be encountered earlier with increasing flow strength, as a remarkable feature in extensional-like flow. The translational self-diffusion increases when increasing either flow strength or electrostatic screening effect in uniform and simple shear flows. Regarding the scaling behavior of static structure factor, the Flory-Edwards exponent decreases with higher values of flow strength and flow type parameters. For the verification, we also examined the image tracking using a fluorescence microscope and the displacing motion of individual molecule.