APS March Meeting 2022
Volume 67, Number 3
Monday–Friday, March 14–18, 2022;
Chicago
Session G42: Dynamics of Ionizable Polymers
11:30 AM–2:30 PM,
Tuesday, March 15, 2022
Room: McCormick Place W-375A
Sponsoring
Unit:
DPOLY
Chair: Gary Grest, Sandia National Laboratories
Abstract: G42.00004 : Insights into the transport mechanisms of water through polymer membranes from quasielastic and inelastic neutron scattering
1:18 PM–1:54 PM
Abstract
Presenter:
Christopher Soles
(National Institute of Standards and Tech)
Author:
Christopher Soles
(National Institute of Standards and Tech)
Polymer membranes that facilitate or inhibit ion transport are critical for a range of technologies, spanning fuel cells, flow batteries, ion exchange columns, and filtration for clean water. A common thread that spans these applications is that their function is coupled to the transport of water through the membrane. There is a significant need to understand the nature by which the water and other penetrants move through the membrane. In this presentation, I will focus on the general case of water diffusion through three types of materials with very different network structures: tightly cross-linked epoxy resins that are used in structural composites and exhibit very little swelling, loosely cross-linked polyamide membranes that are used as the active layer in a reverse osmosis desalination membranes that contain polar groups and exhibit moderate swelling upon hydration, and ion containing block copolymer alkaline fuel cell membranes that contain transient ionic cross-links and swell significantly with water. A combination of techniques will be used to characterize the swollen structure and dynamics of the membrane materials relative to their transport behavior. Positron annihilation lifetime spectroscopy will be used to quantify the intermolecular packing efficiency in the material, small angle neutron scattering will be used to quantify the microstructure of the water-rich domains in the hydrated materials, and a combinate of infrared and nuclear magnetic resonance spectroscopy will be used to quantify interactions between water and the membrane. Quasielastic and inelastic neutron scattering will be used to quantify both the polymer dynamics of the membrane and the dynamics of the water molecules diffusing through the membranes. The insights from these measurements will be used to discuss the different mechanisms that are used to describe water transport in these materials ranging from solution-diffusion to pore-flow transport.