Impact of ion content and electric field on mechanical properties of coarse-grained ionomers.

Using a coarse-grained ionomer model for polyethylene-co-methacrylic acid that includes associating acid groups along with pendant anions and unbound counterions, we investigate how ionomer mechanical behavior depends on the acid and ion content. We find that the modulus and yield stress increase as the ion content increases, at all strain rates considered. This is in agreement with prior experimental results. We also apply a very strong external electric field in the melt state and then cool the system to set the aggregate order induced by the field. We find that the application of electric field increases the modulus in the direction parallel to the field, and we postulate that this is related to the observed increase in aggregate ordering in the direction perpendicular to the field.