Impact of ionic aggregate structure on ionomer mechanical properties from coarse-grained molecular dynamics simulations

Using coarse-grained molecular dynamics simulations, we study ionomers in equilibrium and under uniaxial tensile deformation. The spacing of ions along the chain is varied, allowing us to consider how different ionic aggregate morphologies, from percolated to discrete aggregates, impact the mechanical properties. From the equilibrium simulations, we calculate the stress-stress auto correlation function, showing a distinct deviation from the Rouse relaxation due to ionic associations that depends on ion content. We then quantify the morphology during strain, particularly the degree to which both chains and ionic aggregates tend to align. We also track the location of the ionomer peak in the anisotropic structure factor during strain. The length scale of aggregate order increases in the axial direction and decreases in the transverse direction, in qualitative agreement with prior experimental results. Published by AIP Publishing.