Molecular Dynamics Study of Polystyrene Sulfonate in Dilute Solutions: from Ionomers to Polyelectrolytes

Ionizable polymers are often cast into membranes from solutions, where solutions structure determines the membrane morphology and function in their many applications.  These polymers associate in solutions forming a rich variety of assemblies from random aggregates to well defined micelles, depending on the specific polymer chemistries and topology. Association takes place at very low concentrations, making the conformation of isolated molecules a critical factor in the understanding of the assembly process.  With the working hypothesis that one could drive the micellar structure in solution through tuning the electrostatic interactions, the current study probes the conformation and dynamics of  polystyrene sulfonate in dilute solutions of different dielectric constants using atomistic molecular dynamic simulations. Polystyrene sulfonate with 100 monomers and sulfonation levels from 0 to 95% was studied in implicit solvents with dielectric constants of 7.8, 30, 78, that correspond to that of THF, alcohols and water respectively.  The evolution of the structure of the polymer as the polymer transitions from a non-ionic polymer to ionomers and to polyelectrolytes, as the dielectric constant is varied will be presented and compared to the conformations in explicit solvents.