Molecular dynamics simulation study has been carried out to investigate intermolecular structure, solvation and thermodynamic behavior of micelle as function of hydrophobic fraction of copolymer (XPS) for unionized (f = 0) and fully ionized (f = 1) states of electrolyte block. Micelle formation occurs via self-aggregation of PSx-b-PMAy copolymer chains with PS core and PMA corona. PMA chains aggregate on the surface of the PS core at f = 0 and being extended as the classic corona at f = 1. The time evolution of micelles from randomly dispersed unimers to micelle formation follow three stages: unimers consumption to form dimer, trimer and small aggregates, fusion/ fission among small cluster, and slow exchange of chains between micelles. The shape of micelle transforms from spherical to ellipsoid with an increase in XPS and size of micelle increases with XPS. The charged PMA blocks show more favorable interaction with surrounding water molecules as compared to uncharged blocks due to the presence of COO- groups. The SASA of micelle increases with XPS in both states, commensurate with its shape transformation. Furthermore, SASA per corona chain shows linear behavior with XPS, in good agreement with experimental behavior of crew-cut micelles in literature. The results of atom density profiles, solvation enthalpy, and RDFs of copolymer-Na+ ion pairs confirm the existence of the polyelectrolyte micelle in the osmotic regime, at all copolymer compositions, in agreement with results of mean-field theory. Micelle exhibits thermodynamically favorable interaction with surrounding water molecules. Electrostatic interactions are the dominant factor in the formation and solvation of the micelle in aqueous solution. The aspects of the micelle structure, equilibrium solvation, intermolecular structure and molecular thermodynamics are in qualitative agreement with experimental studies on this system

Molecular dynamics study of asymmetric poly(styrene)-block-poly(methacrylic acid) polyelectrolyte-neutral diblock copolymer micellization in aqueous solution

ACS Fall 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.