Enhanced Hydrogen Bonding via Epoxide-functionalization Restricts Mobility in Poly(ethylenimine) for CO2 Capture

Abstract

Epoxide-functionalization has emerged as an effective strategy for enhancing the oxidative stability of poly(ethylenimine)-based CO2 capture sorbents. However, the underlying mechanism remains largely unexplored. Here we combine first-principles modeling, material synthesis, and characterizations to investigate the impact of epoxide-functionalization on hydrogen bonding and mobility in poly(ethylenimine) (PEI). Blue-moon ensemble and deep potential molecular dynamics simulations reveal that epoxide-functionalization leads to stronger hydrogen bonding involving hydroxyl groups. Synthesized branched PEI samples with and without propylene-oxide (PO) functionalization are characterized using DSC, NMR relaxometry, and fluorescent probes, demonstrating that PO-functionalization significantly reduces BPEI mobility. These findings suggest that the enhanced oxidative stability of epoxide-functionalized PEI can be attributed to the formation of strong hydrogen bonds with hydroxyl groups, which restrict the mobility of PEI and decelerate mobility-dependent radical propagation reactions responsible for polymer degradation. Strategies for further tuning hydrogen bond environment are proposed based on these findings.

Fundamental Insight into Humid CO2 Uptake in Direct Air Capture Nanocomposites Using Fluorescence and Portable NMR Relaxometry

“…Ratiometric analysis was used to assess additional physical phenomena in that work, including polymer hysteresis. In a second study, Li et al demonstrated that a similar ratiometric analysis of THPE emission could serve as a measure of the relative mobility of several different epoxide-functionalized aminopolymers with different degrees of hydrogen bonding . Fluorescence data was correlated with NMR relaxometry data to provide more quantitative analysis of polymer mobility.…”