Rouse Dynamics of Polyelectrolyte Solutions:  Molecular Dynamics Study

Abstract

We performed molecular dynamics simulations of dilute and semidilute polyelectrolyte solutions without hydrodynamic interactions to study Rouse dynamics of polyelectrolytes. Polyelectrolyte solutions are modeled by an ensemble of bead-spring chains of charged Lennard-Jones particles with explicit counterions. The simulations were performed for partially and fully charged polymers with the number of monomers N ) 25-373. We show that the simulations of the Rouse dynamics give qualitatively similar results to the experimentally observed dynamics of polyelectrolyte solutions. Our simulations showed that the chain relaxation time depends nonmonotonically on polymer concentration. In dilute solutions, this relaxation time exhibits very strong dependence on the chain degree of polymerization, τ ∼ N 3 . The chain relaxation time decreases with increasing polymer concentration of dilute solutions. This decrease in the chain relaxation time is due to chain contraction induced by counterion condensation. In the semidilute solution regime the chain relaxation time decreases with polymer concentration as c -1/2 . In this concentration range the chain relaxation time follows the usual Rouse scaling dependence on the chain degree of polymerization, τ ∼ N 2 . At high polymer concentrations the chain relaxation time begins to increase with increasing polymer concentration. The crossover polymer concentration to the new scaling regime does not depend on the chain degree of polymerization, indicating that the increase in the chain relaxation time is due to the increase of the effective monomeric friction coefficient. The analysis of the spectrum and of the relaxation times of Rouse modes confirms the existence of the single correlation length , which describes both static and dynamic properties of semidilute solutions.

Solution properties of star polyelectrolytes having a moderate number of arms

“…Previous theoretical efforts rationalized this counter-intuitive trend as being due to counter-ion condensation. 90–93 We find a similar behavior for star polyelectrolytes having f = 4 arms. However, for star polyelectrolytes having f > 4 arms, we observe a significant change in behavior of F ( q, t ), reflecting structural changes in the polyelectrolyte solution.…”

Salt Effect on Osmotic Pressure of Polyelectrolyte Solutions: Simulation Study

“…In our simulations polyelectrolytes were modeled by chains of charged Lennard-Jones (LJ) particles with diameter σ and degree of polymerization N = 300 [23,32,34,35]. Each monomer on the polymer backbone was positively charged.…”

Molecular and nanoscale factors governing pressure‐sensitive adhesion strength of viscoelastic polymers

“…A polymer chain diffuses a distance on the order of its size during a time interval proportional to the chain relaxation time. 82 In turn, both diffusion and relaxation properties contribute to adhesion. 83 Equations 6 and 12 establish a link between adhesion, free volume, intermolecular cohesion, relaxation, diffusion, and friction of polymers.…”

“…Clearly, the relaxation process involves diffusion as one of the main mechanisms. 81,82 Because pressure-sensitive adhesion is a material response to applied mechanical stress, the role of relaxation in providing both good adhesive contact and adhesive joint strength is significant. The significance of relaxation processes in pressure-sensitive adhesion remains insufficiently explored 83,[116][117][118][119] and poorly understood, although such investigation does not require sophisticated methods such as the techniques used for the study of self diffusion or free volume.…”