Ion Transport and Rheological Behavior in Polymeric Systems

Author: Tsamopoulos, Alexandros

Year: 2026

Degree: Dissertation (Ph.D.)

Advisor: Wang, Zhen-Gang

Committee Members: Brady, John F.; Datta, Sujit; Kornfield, Julia A.; Wang, Zhen-Gang

Option: Chemical Engineering

Abstract

Ion-containing polymers are an important class of soft materials, owing to their applications in electrochemical energy storage, fuel cells, and membrane separations, as well as their rich ion transport and mechanical behavior. Their properties are governed by the interplay of polymer connectivity, ion correlations, segmental dynamics, and viscoelastic response across multiple length and time scales. This thesis examines these couplings using molecular simulations of polymer electrolytes, polymerized ionic liquids, and model polymeric fluids. We first investigate ion transport in salt-doped polymer electrolytes and show how temperature and salt concentration jointly control ionic conductivity through their effect on polymer mobility. We then examine polymerized ionic liquids, focusing on how ion correlations and chain length influence polymer relaxation, Onsager transport coefficients, and ion conductivity. Next, we return to the polymer electrolyte system to study the role of salt in controlling their linear and nonlinear rheological response. Finally, we develop a hydrodynamic framework for the diffusion of anisotropic probes in complex fluids, demonstrating that probe motion is governed by the length-scale-dependent viscous response of the surrounding medium. Overall, the range of systems considered here reflects the broader challenge of understanding ion-containing and polymeric materials.