Understanding Molecular Packing within Ionomer Domains of Materials Characterized by Small Angle Scattering

Ionomers are a class of charged polymers that typically contain less than 15 mol% iononized or acidic pendant groups bonded to a low dielectric polymer backbone. [1] Materials containing ionomers are used in many applications including adhesives, coatings, and membranes. Perfluorosulfonic acid (PFSA) (e.g., Nafion) is one such example used in proton-exchange membranes due to its high proton conductivity and mechanical stability in the hydrated state. There is considerable interest in understanding the molecular packing and morphology in these PFSA materials and linking structure to the ion-conducting and mechanical properties. Structural characterization of PFSA materials typically involve small angle and wide-angle scattering with small angle X-ray scattering profiles of hydrated PFSA exhibiting a characteristic “ionomer peak”. Analytical model fits or computational approaches like CREASE [2] are needed to link the ionomer peak in SAXS profiles to hydrophilic ionomer domain sizes and shapes. To elucidate the molecular packing within the domains that give rise to the ionomer peak, we are conducting dissipative particle dynamics (DPD) simulations; this talk will present these simulation results.

[1] Zhang, L. H., et al. (2014) Macromolecular Reaction Engineering 8(2): 81-99.

[2] Heil, C. M., et al. (2022) ACS central science 8(7): 996-1007.