  This simulation study investigates the dependence of the structure of dry
Nafion$^{\tiny\textregistered}$-like ionomers on the electrostatic interactions
between the components of the molecules. In order to speed equilibration, a
procedure was adopted which involved detaching the side chains from the
backbone and cutting the backbone into segments, and then reassembling the
macromolecule by means of a strong imposed attractive force between the cut
ends of the backbone, and between the non-ionic ends of the side chains and the
midpoints of the backbone segments. Parameters varied in this study include the
dielectric constant, the free volume, side-chain length, and strength of
head-group interactions. A series of coarse-grained mesoscale simulations shows
the morphlogy to depend sensitively on the ratio of the strength of the
dipole-dipole interactions between the side-chain acidic end groups to the
strength of the other electrostatic components of the Hamiltonian. Examples of
the two differing morphologies proposed by Gierke and by Gebel emerge from our
simulations.
