LAUSR

Abstract Crosslinked poly(ethylene oxide) (PEO) membranes are attractive for performing CO 2 separations. However, the effects of crosslink density on CO 2 separation performance vary widely among reported crosslinked PEO systems, while crosslink inhomogeneity, the uneven distribution of crosslinks in the network, has been largely unexplored. This work reports on a series of PEO-based, model crosslinked membranes with systematically varied crosslink density and crosslink inhomogeneity. Crosslink density was controlled via end-crosslinking commercial Jeffamine ® polyetheramines of specific molecular weight of 148, 600, 900, or 2000 g/mol with an epoxy terminated PEO; the distribution of crosslinks was controlled by the timed addition of PEO diamine oligomers of differing molecular weight. Three distinct series of networks were produced in increasing crosslink inhomogeneity levels: unimodal, bimodal, and clustered. It was found that while decreasing crosslink density is a prominent factor in increasing CO 2 permeability, further improvements in overall CO 2 separation performance were realized by adjusting crosslink inhomogeneity. In particular, both the bimodal and clustered films outperformed respective unimodal films in CO 2 permeability and CO 2 /H 2 selectivity, suggesting the important role of crosslink inhomogeneity in dictating gas transport properties. These crosslinked PEO films approach or surpass the most recent Robeson upper bounds for pure gas CO 2 /H 2 and CO 2 /N 2 separations, making them attractive membranes for H 2 purification and carbon capture.