MULTISC ALE MODELING OF NAFION MECHANICAL PROPERTIES

摘要

Multiscale modeling is used to investigate the mechanical characteristics of ionic polymers with the intent of ultimately expanding understanding of the interplay between multiscale stiffness and electromechanical response. Strategies for manipulating electromechanical transduction of ionic polymers include, but are not limited to: variation of hydration and/or the equivalent weight. In general, variations resulting in increased electroactive response also result in decreased mechanical stiffness and can decrease to the point of limiting mechanical integrity. This effort begins with the supposition that a better understanding of the ionic polymer multiscale material stiffness will enable bypass of this perceived trade-off. Rotational Isomeric State (RIS) theory is used to predict the conformation of a typical polymer hydrophobic backbone for a fully hydrated, sodium exchanged, Nafion 1200 EW case. The RIS method generates a large number of crosslink-to-crosslink chain lengths. The distribution is assessed via Johnson distributions and in turn, employed in a Boltzmann statistical thermodynamics framework to assess mechanical stiffness. The approach explores the impact of morphology on stiffness via imposing as assumed morphology a priori.