Salt effects on knot dynamics in polyelectrolyte solutions

Abstract

ABSTRACT We study the dynamics of linear polyelectrolyte (PE) knot in solution with doping salt by molecular dynamics simulations. The molecular mechanisms of PE knot dynamics are explained. The knot dynamics are the coupling results by the moving effect of chain entanglement and by the breathing effect of knot fluctuations. The moving effect is important as the whole chain is in the random coil state and becomes weak as shrinking to the close-to-globule (CTG) state. Interestingly, as the chain in the CTG state, the knot swells with occupying more segments. The breathing effect dominates the knot dynamics in the CTG state. This nontrivial behaviour (in comparison to neutral polymer knot) is prominent for the cases of doping salt with high concentration or of doping high-valent salt, which attributes to the enhanced electrostatic interactions and long-range fluctuation effects.