From Atomistic and Mesoscopic Insight to Macroscopic Shear Response of Ionizable Polymers

The shear response of Ionizable polymers results from a series of dynamic events that take place on different time and length scales from those of the ionic clusters, to segmental dynamics and stretching recoiling of the entire chains. The structure evolution of the ionic assemblies and their impact on polymer dynamics remain an open fundamental question that affects the integration of these macromolecules into device applications. Here, using fully atomistic molecular dynamics simulations, we will introduce shear response of sulfonated polystyrene polyelectrolytes Na-SPS with ionizable fractions of f=0.9, f=0.20, and 0.35, in pristine and THF-swollen melts from the atomistic level to macroscopic response.

We show that with increasing sulfonation fraction from the ionomers to polyelectrolytes the spherical clusters in the ionomer regime evolve into highly branched assemblies with a broad size distribution in both pristine and swollen melts, with Na⁺ counter ions condensed for all systems. The macroscopic motion of the polymer is highly constrained. The correlation between the dynamics of the ionic groups that constitute the clusters, chain stretching and chain flipping, each occurring on a district time and length sales and the viscosity of the systems will be discussed.