Exploring the Structure-Property Relationships of Linear and Crosslinked Poly(ethylene Oxide) Polymer Membranes for Gas Separations

The development of polymeric materials suitable for gas separation membrane applications is discussed in this dissertation. Compared to conventional gas separation systems, such as absorption, gas separation membrane systems are inherently smaller in size and easier to operate, and potentially, more economically viable. Membranes with high permeability (for a high gas throughput) and adequate selectivity (ability to separate a given gas from a mixture) are desired. However, due to the natural properties of polymeric materials, generally, membranes with high permeabilities unfortunately operate with low selectivities and vice versa. To combat this natural trade-off, to produce materials with both high permeabilities and sufficiently high selectivities, the chemical and physical properties of polymeric materials must be strategically designed.

The majority of this work explores strategies for incorporating rubbery poly(ethylene oxide) (PEO) into gas separation membranes. PEO is a promising material for CO₂ related-separations due to its high solubility selectively for CO₂ and its high diffusivity, which together, give PEO-based materials excellent CO₂-separation performance. However, pure PEO is mechanically weak and suffers from high crystallinity which prevent its use in gas separation membranes. Therefore, this work explores strategies to incorporate PEO into copolymers, into crosslinked networks, and into semi-interpenetrating networks (s-IPNs). These systems have demonstrated improved mechanical properties, mitigated PEO crystallinity, and highly promising CO₂-related gas separation performance.