Polymer dynamics and the performance of amine containing polymers for separating carbon dioxide from the ambient atmosphere

Polymer membranes and sorbents are an important component of direct air capture strategies for removing carbon dioxide (CO2) from the ambient atmosphere. Branched polyethylimeimine (PEI) is one of the most popular aminopolymer sorbents being used for CO2 capture applications. However, fundamental knowledge about the CO2 adsorption/desorption mechanisms as a function of temperature, humidity, and amine population in PEI are critically needed to develop improved CO2 sorbents. While many studies to date have focused on CO2 sequestration performance of PEI or derivatized composites, very few have examined polymer-sorbate interplay and resulting effects of sorption on dynamics. In this presentation, we demonstrate that quasielastic neutron scattering (QENS) is useful to probe dynamics before and after exposure to water and/or CO2. We found that each dosing condition, as well as the nature of the amine groups, separately influences diffusive behavior. The results from QENS experiments are coupled with findings from other physiochemical characterization methods to provide a holistic view of molecular sorption in PEI.