Simulation Study of the Conformational Properties of Diblock Polyelectrolytes in Salt Solutions

Abstract

Coarse‐grained molecular dynamics simulations are performed to understand the behavior of diblock polyelectrolytes in solutions of divalent salt by studying the conformations of chains over a wide range of salt concentrations. The polymer molecules are modeled as bead spring chains with different charged fractions and the counterions and salt ions are incorporated explicitly. Upon addition of a divalent salt, the salt cations replace the monovalent counterions, and the condensation of divalent salt cations onto the polyelectrolyte increases, and the chains favor to collapse. The condensation of ions changes with the salt concentration and depends on the charged fraction. Also, the degree of collapse at a given salt concentration changes with the increasing valency of the counterion due to the bridging effect. As a quantitative measure of the distribution of counterions around the polyelectrolyte chain, we study the radial distribution function between monomers on different polyelectrolytes and the counterions inside the counterion worm surrounding a polymer chain at different concentrations of the divalent salt. Our simulation results show a strong dependence of salt concentration on the conformational properties of diblock copolymers and indicate that it can tune the self‐assembly behaviors of such charged polyelectrolyte block copolymers.

Multivalent Salt-Induced Self-Assembly of Amphiphilic Polyelectrolytes of Different Charge Fractions: A Coarse-Grained Molecular Dynamics Simulation Study

“…The self-assembly of amphiphilic diblock and triblock PEs has been studied under salt-free conditions using coarse-grained Langevin dynamics simulations at various charge fractions. , The conformational properties of diblock PEs in solutions of divalent salt were studied at various charge fractions over a wide range of salt concentrations . However, given the ion size and salt valency taken into account, no overcharging of the polymer was observed.…”

Self-assembly of amphiphilic polyelectrolytes in trivalent salt solution

“…As compared with monovalent counterions, much stronger electrostatic interactions and ion-ion correlation can be induced by multivalent ions. 19 It has been proved that short-range electrostatic attractive forces between like-charged systems can be created by the ion-ion correlation in the presence of trivalent ions. [20][21][22][23][24] The attraction between colloids is essential for the self-organized superstructures.…”