Highly CO₂-Selective Gas Separation Membranes Based on Segmented Copolymers of Poly(Ethylene oxide) Reinforced with Pentiptycene-Containing Polyimide Hard Segments

Abstract

Poly(ethylene oxide) (PEO)-containing polymer membranes are attractive for CO2-related gas separations due to their high selectivity toward CO2. However, the development of PEO-rich membranes is frequently challenged by weak mechanical properties and a high crystallization tendency of PEO that hinders gas transport. Here we report a new series of highly CO2-selective, amorphous PEO-containing segmented copolymers prepared from commercial Jeffamine polyetheramines and pentiptycene-based polyimide. The copolymers are much more mechanically robust than the nonpentiptycene containing counterparts due to the molecular reinforcement mechanism of supramolecular chain threading and interlocking interactions induced by the pentiptycene structures, which also effectively suppresses PEO crystallization leading to a completely amorphous structure even at 60% PEO weight content. Membrane transport properties are sensitively affected by both PEO weight content and PEO chain length. A nonlinear correlation between CO2 permeability with PEO weight content was observed due to the competition between solubility and diffusivity contributions, whereby the copolymers change from being size-selective to solubility-selective when PEO content reaches 40%. CO2 selectivities over H2 and N2 increase monotonically with both PEO content and chain length, indicating strong CO2-philicity of the copolymers. The copolymer film with the longest PEO sequence (PEO2000) and highest PEO weight content (60%) showed a measured CO2 pure gas permeability of 39 Barrer, and ideal CO2/H2 and CO2/N2 selectivities of 4.1 and 46, respectively, at 35 °C and 3 atm, making them attractive for hydrogen purification and carbon capture.

Enhanced CO2 separation performance of P(PEGMA-co-DEAEMA-co-MMA) copolymer membrane through the synergistic effect of EO groups and amino groups

“…Additionally, the intensity of the PEO peaks (e.g., 2870 cm -1 ) increased with increasing PEO weight content, as expected 29. A strong band at 1730 cm -1 was observed in all PEDM copolymers due to the stretching vibration of carbonyl (C=O) bonds, and the position of this band did not change with changes in composition.…”

“…47 They thought that difference in the permeability of CO 2 and N 2 implied that transport of CO 2 followed both facilitated transport mechanism and solution-diffusion mechanism, while the permeability of nonpolar N 2 only followed the solution-diffusion mechanism. 20,29,[50][51][52][53] 48 CO 2 /N 2 selectivity show a decreased trend mainly due to the decrease of CO 2 permeability.…”

Preparation and characterization of polyimides containing triaryl imidazole side groups

“…Aromatic polyimides (PIs) are one of the most significant high performance materials due to their attractive properties including excellent mechanical properties, outstanding thermal stability, high glass transition temperature, and good resistance to organic solvents . They have been widely applied as components for microelectronic and optoelectronic devices, gas separation membranes, and high‐temperature materials for the aerospace industry . However, aromatic PIs are difficult to process because of low solubility in most organic solvents and high melting or glass transition temperatures, hence restricting their applications.…”

Blending PPO‐based molecules with Pebax MH 1657 in membranes for gas separation

“…More specifically, favorable quadrupole–dipole interactions between CO 2 and the ethers make such materials interesting for both pre‐ and post‐combustion applications . Use of EO functional groups in stable membrane structures is not trivial because of the poor film‐forming ability of pure poly(ethylene oxide) (PEO) . Additionally, the crystallization behavior of pure PEO with molecular weights (MW) above 1 kDa appears detrimental for gas transport …”