Structure and Dynamics of Soft Matter

点击翻译按钮获取中文摘要

With this Discovery Grant, I will study the morphology of ion-conducting polymers, with the long-term goal of improving material properties of polymer electrolyte membranes (PEMs) for fuel-cell applications. Good proton conductivity in PEMs depends on polymer morphology and ionic nanostructure. Controlling this morphology is essential to the design of high-performance membranes. These experiments will contribute to the fundamental understanding necessary to optimize polymer design for these applications, and ultimately aid our transition to a low-carbon society. ******These studies will address current challenges in PEM research: to reduce emphasis on fluorine-based polymers through development of robust hydrocarbon-based ionomers, to improve polymer lifetime, and to improve durability. One focus will be a series of hydrocarbon-based, proton-conducting polymers designed to offer an alternative to fluorine-based systems. This material is a random copolymer but early studies show some phase separation at nm length scales; we will study the morphology to determine the nature of the phases and inform the next generation of these polymers. My research group and I will also study a new hydrocarbon-based, anion-conducting random copolymer, designed for use in alkaline fuel cells where the alkaline environment allows for the use of much cheaper catalysts. Our recent studies show no evidence of ion-clustering and indicate that water is distributed at sub-nm length scales; we will elucidate conductivity mechanisms. Finally, this research will contribute to understanding polymer lifespans through studies of degradation of Nafion™, the polymer most commonly used in fuel cell applications. In particular, we will study how the morphology changes during standard degradation tests.******The main experimental methods that we use are based on scattering of radiation from materials. My research group now has access to a wide range of length scales through light-scattering instruments in my lab (small-angle and classic, length scales from 10 microns to 20 nm) and a recently installed small-angle X-ray scattering instrument in Simon Fraser University's materials facility (length scales from 20 nm to 0.2 nm). We also use neutron scattering to provide complementary information. These tools allow us to study a wide range of behaviour: aggregation of polymer molecules, micro-phase separation, ion-clustering, polymer backbone ordering, and order at the monomer level. Recently, we have successfully used molecular dynamics simulations to complement our measurements at the smallest length scales and plan to continue to develop this capability.