Engineering Commons^™

Mass And Charge Transport In Hydrated Polymeric Membranes, Marshall T. Mcdonnell

Doctoral Dissertations

Mass and charge transport through hydrated polymer membranes has significant importance for many areas of engineering and industry. Multi-scale modeling and simulation techniques were used to study transport in relation to two specific membrane applications: (1) food packaging and (2) additives for polymer electrolytes.

Chitosan/chitin films were studied due to their use as a sustainable, biodegradable food packaging film. The effects of hydration on the solvation, diffusivity, solubility, and permeability of oxygen molecules in these films were studied via molecular dynamics and confined random walk simulations. With increasing hydration, the membrane was observed to have a more homogeneous water distribution …

Ab Initio Studies Of Proton Transport In Proton Exchange Membranes, Jeffrey Keith Clark

Doctoral Dissertations

A molecular-level understanding of the factors that contribute to transport properties of proton exchange membranes (PEMs) for fuel cell applications is needed to aid in the development of superior membrane materials. Ab initio electronic structure calculations were undertaken on various PEM ionomer fragments to explore the effects of local hydration, side chain connectivity, protogenic group separation, and specific side chain chemistry on proton dissociation and transfer at low hydration. Cooperative interactions between both intra- and inter-molecular acidic groups and hydrogen bond connectivity were found to enhance proton dissociation at very low degrees of hydration. The energetics associated with proton transfer …

Membrane And Performance Study In Polymer Electrolyte Membrane Fuel Cells And Hydrogen Bromine Redox Flow Batteries, Yujia Bai

Doctoral Dissertations

This dissertation represents the consideration of the problems of polymer electrolyte membrane fuel cells (PEMFC) and hydrogen-bromine redox flow batteries (RFB). Due to the importance of water management in PEMFCs, all the experiments were strictly controlled at different water hydration conditions. Water uptake and densities were measured for Nafion^® and a series of 3M ionomer membranes. The thermodynamics of water and polymer was analyzed based on water uptake experiment and calorimetry. Furthermore, partial molar volumes (PMV) of water/membrane system was defined for the first time and used to analyze the interaction between water and polymers. Three states of water …