Tailoring Crosslinked Polyether Networks for Separation of CO₂ from Light Gases

Abstract

Crosslinked poly(ethylene oxide) or poly(ethylene glycol) (PEG) is an ideal membrane material for separation of CO2 from light gases (e.g., H2, N2, O2, CH4 etc). In these membranes, crosslinking is used as a tool to suppress crystallinity of the PEG segments. In spite of the extensive effort to develop crosslinked PEG membranes in the last two decades, it remains a challenge to establish the structure–property relationships. This paper points out the fundamental limitations to correlate the chain topology of a network with the gas permeation mechanism. While a quantitative comparison of the molecular weight between crosslinks of networks and gas permeation mechanism reported by different research groups is challenging, effort is made to draw a qualitative picture. In this review, a focus is also put on the progress of utilization of dangling chain fractions to tailor the gas permeation behavior of PEG networks.

Mechanical Behavior of 3D Printed Poly(ethylene glycol) Diacrylate Hydrogels in Hydrated Conditions Investigated Using Atomic Force Microscopy

“…§: Projected light direction; ≡: printing direction; ▲: amount of available residual free radicals at the top and bottom of a cross-linked layer; ★: empty pockets of voids swollen due to water uptake. Adapted by the authors from Figure 2, p6 49 licensed under CC BY.…”

“…Figure 4. Schematic of the prepolymer solution (top left), single cross-linked layer (top middle), two different cross-linking densities at the top and bottom of each layer (top right),49 and two consecutive cross-linked layers with different amounts of cross-linking at the interface (bottom middle). §: Projected light direction; ≡: printing direction; ▲: amount of available residual free radicals at the top and bottom of a cross-linked layer; ★: empty pockets of voids swollen due to water uptake.…”

Cross-Linked Polymer Membranes for Energy-Efficient Gas Separation: Innovations and Perspectives

“…It was observed that gas permeability and diffusivity coefficients increased significantly with decreasing cross-link density and then leveled off slowly with further decreased cross-link density. A possible explanation is that physical entanglements of segments have dominant effects that restrict chain mobility when the inter-cross-link chain length is above the entanglement chain length . Further increasing the theoretical intensity does not influence chain entanglements and chain mobility, leading to relatively constant permeability and diffusivity coefficients.…”

Membranes for Osmotic Power Generation by Reverse Electrodialysis

“…Thus, the FCD of a crosslinked membrane can be tuned by varying the degree of crosslinking and IEC. There are several metrics expressing the degree of crosslinking of a crosslinked polymer network: the concentration of elastically active chains ν el /V 0, the crosslink density μ el /V 0 , the cycle rank density, ξ/V 0 , and the averaged molecular weight of the polymer chains between the crosslinked points, M C , where ν el is the number of elastically active chains, μ el is the number of crosslinks, ξ is the number of independent circuits in the network (cycle rank) and V 0 is the volume of the dry polymer network [ 46 , 47 , 48 ]. To the best of my knowledge, the FCD, selectivity and resistance of the membrane have never been investigated for a crosslinked membrane where any of these metrics expressing the degree of crosslinking was known.…”