We are developing and applying the following advanced tools to measure the structure, dynamics, and performance of polymer-based membranes:
We employ polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS) to study the functional group concentrations with thin membranes. One advantage of the PM-IRRAS technique is that it allows IR measurements to be conducted in humid environments, as only the water that is absorbed in the film is detectable (ambient moisture and carbon dioxide is suppressed). This allows us to conduct IR measurements as a function of water content (i.e. swelling) within a membrane.
NMR is a powerful analytical tool for observing segmental dynamics in chain molecules as well as the rotational and translational diffusion processes of low molar mass solute molecules contained within functional polymers such as water filtration membranes and fuel cells. NMR relaxation and pulsed field gradient methods are utilized to study the types of motion that occur and are useful discriminating between models of dynamics in complex systems. We employ these NMR methods as well as lineshape analysis and exchange experiments to probe molecular dynamics on microsecond to second time scales.
Electrochemical Impedance Spectroscopy
Neutron scattering can investigate both structure and dynamics of soft materials and membranes. When a neutron interacts with an atom within a sample, the scattering event can be elastic, inelastic or quasi-elastic. Elastically scattered neutrons yield useful information about the structure (i.e. spatial arrangement in space) of the membrane, whereas inelastic and quasi-elastically scattered neutrons yield information about the dynamics (i.e. how things move in space and time) within the membrane. By contrast matching, we can probe the structure and/or dynamics of the membrane, water, or both.