Understanding the Role of Hydroxyl Functionalization in Linear Poly(ethylenimine) for Oxidation-Resistant Direct Air Capture of CO2

Aminopolymer-based adsorbents are a prominent class of materials being used for direct air capture of CO2 at the industrial scale. However, improving their working lifetime, specifically by increasing their resilience to oxidative degradation, remains an ongoing challenge. Towards this end, functionalization of aminopolymers with non-amine functionalities such as hydroxyls has emerged in recent years as a promising strategy towards improving adsorbent lifetime. Although there is a growing body of work demonstrating the effectiveness of this approach and investigating the origin of this improved stability, studies to date have primarily focused on branched aminopolymer systems such as branched poly(ethylenimine). In this work, we use hydroxyl-functionalized linear poly(ethylenimine) to continue to probe the underlying protective mechanism of this strategy. A combination of thermogravimetric analysis, NMR relaxometry, differential scanning calorimetry, and computational simulations is used to better understand the relationship between extent of chemical functionalization, physical properties, and adsorbent performance.