(519a) Effect of Co Ions in Cross-Linked Poly(ethylene oxide) on O2 Transport Characteristics

Cobalt (Co)-based complexes are considered as attractive O₂-binding elements, which can reversibly and selectively interact with O₂ and affect O₂ gas transport properties. Herein, we investigate the effect of Co ions dissociated in amorphous cross-linked poly(ethylene oxide) (XLPEO) on physical properties and gas transport characteristics. Polymeric films containing Co salts were prepared by photo-polymerization of solutions containing poly(ethylene glycol) diacrylate (PEGDA), poly(ethylene glycol) methyl ether acrylate (PEGMEA), and different salts such as Co(ClO₄)₂, and Co(BF₄)₂. The salts can be fully dissociated, and the Co²⁺ ions form conjugations with the ethylene oxide in XLPEO, as validated by FTIR and XRD. Increasing the Co content increases the density (following the additive model) and glass transition temperature of XLPEO. For instance, adding 17 wt.% Co(ClO₄)₂ to XLPEO increases the T_g and density from -65 ºC and 1.149 g/cm³ to -26 ºC and 1.304 g/cm³, respectively. The O₂ and N₂ permeability are significantly impacted by adding high concentration of Co salts. Specifically, O₂ and N₂ permeability decreases from 26 and 10 to 0.24 and 0.14 Barrer, respectively, by adding 17 wt.% of Co(BF₄)₂. Interestingly, the CO₂/O₂ selectivity increases from 20 to 60 by addition of 17 wt.% of Co(BF₄)₂ presumably due to the retarded O₂ diffusion. Additionally, we found that O₂ solubility increases with increasing Co(BF₄)₂ content due to high affinity between Co ions and oxygen. For example, O₂ solubility increases from 0.2 to 6.4 cm³(STP)/cm³ atm at 35°C by addition of 6.4 wt.% Co(BF₄)₂ to XLPEO. Understanding the effect of Co ions-O₂ interactions on gas transport properties may provide guidance in designing advanced polymeric membranes with high CO₂/O₂ selectivity.