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Presenter: Chris J. Cornelius, PhD, Dept of Chemical Engineering, Univ. of Nebraska - Lincoln
Date: 3/19/2018
Time: 3:10 pm
Location: EN 1045
Contact Email:

Topic: Tuning Quaternary Ammonium Ionomer Properties Using Composition and Processing to Improve Flow Battery and Water Desalination
Abstract: Abstract
Structure, property, and function relationships must be coupled to theory and previous art in order to design new materials. Ionomer composition and morphology impacts functional group distribution, water and ion transport, and physical properties related to toughness, and degradation resistance. Controlling polymer chain motion, swelling, and charge distribution is critical to selective molecule transport. A dichotomy exists between ion conductivity and the physical properties of an ionomer. Typically, a property trade-off is encountered affecting long-term durability. Increasing the degree of sulfonation (DS) improves ion conductivity, but leads to undesirable water swelling that degrades strength, and dimensional stability. Numerous synthetic efforts are devoted to creating simultaneous improvements in ion transport and physical properties. One promising material is poly(b-(t-butyl styrene)-b-(ethylene-co-propylene)-b-(styrene-co-styrene sulfonate)-b-(ethylene-co-propylene)-b-(t-butyl styrene)) (PBC) developed by Kraton Polymers. Interestingly, its film morphology was dramatically altered when solution-cast into a film using tetrahydrofuran (THF) versus a cyclohexane:heptane (C:H) mixture. Film property and morphology changes were evaluated using Transmission Electron Microscopy (TEM), Small-Angle X-ray Scattering (SAXS), and electrochemical impedance spectroscopy. These changes were compared to Nafion 117 and Nafion 212. Average sulfonated inter-domain spacing through the film’s thickness increased from 22.3 nm (C:H cast) to 30.5 nm (THF cast) that was estimated using SAXS. TEM revealed that PBC solution-cast films from C:H contained a random distribution of discrete sulfonated domains. An ordered PBC morphology consisting of lamella and hexagonally packed ion groups were created from a THF solution-cast film. These changes were attributed to favorable solvent-ionomer interactions during solvent evaporation and film densification. This ordered morphology led to increased conductivity (4.5 mS/cm versus 47.8 mS/cm), improved fuel cell power (19 mW/cm2 versus 160 mW/cm2), enhanced ionomer actuation (3.0 cm versus 6.9 cm), and modest self-discharge improvements for a vanadium redox-flow battery. These results demonstrate that morphology and composition impact ionomer physical properties, transport, and device function. Fundamental material science efforts are critical to the creation of new knowledge and transformative technologies. However, understanding and controlling material assembly is a cornerstone of material science. The focus of this talk will be an examination of material type and organizational structure at multiple scale lengths as well as organic-inorganic nanocomposites. Initial results reveal that spatial organization of ion domains is a critical factor in the reduction of energy utilization or its use to store and efficiently release energy.

Professor Cornelius is a faculty member in the Department of Chemical and Biomolecular Engineering at the University of Nebraska - Lincoln (UNL) and Editor of the Journal of Materials Science. His work investigates fundamental material interrelationships between structure, physical properties, and transport using synthetic polymers, ionomers, hybrid organic-inorganic materials, and sol-gel glasses. He teaches graduate and undergraduate thermodynamics, polymer physics, transport phenomena, and separations. Before academia, he was a staff scientist at Sandia National Laboratories working on the developing hydrocarbon ionomers, fuel cells (DMFC, PEM, AEM), and gas separations (sol-gel films and polyimide nanocomposites). This work resulted in numerous collaborations with industry (Sharp Corporation, GM, Ford, Ballard, Toyota, Honda, Exxon Mobil, Chevron Texaco, Teledyne, United Technologies), National Laboratories (LANL, PNNL, ONR, Savannah River), and university faculty throughout the world. Prior to his PhD, he was as a Process Engineer at 3M working on non-woven media for particle filtration and a Research Engineer with Dow Plastics producing metallocene-based polyolefins. He uses these experiences to enrich the research, scholarship, and learning domains at UNL.

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