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

Abstract

Amphiphilic polymers with both hydrophobic and hydrophilic blocks are of great interest for their potential applications in drug delivery. Their self-assembly behavior in response to environmental factors like ion charge and multivalent salt concentration has been the subject of recent investigation. Our study utilizes coarse-grained molecular dynamics simulations to investigate the aggregation behavior of amphiphilic copolymers upon introducing tetravalent salt at varying charge fractions. We identify a critical concentration, Cs*, where the aggregation number reaches its maximum for each charge fraction, followed by a subsequent decrease at the excessive salt regime. This study reveals distinct morphological transitions in response to increasing salt concentration and decreasing charged fractions, namely, (i) stable dispersed micelles, (ii) a singular micelle comprising all copolymer chains, and (iii) redispersed micelles, particularly evident at lower charged fractions. Our study highlights the significant influence of tetravalent salt and charge fractions of polyelectrolyte chains on the self-assembly behavior of polyelectrolyte copolymers.