High-Loading Poly(ethylene glycol)-Blended Poly(acrylic acid) Membranes for CO Separation.

Poly(ethylene glycol) (PEG) is an amorphous material of interest owing to its high CO affinity and potential usage in CO separation applications. However, amorphous PEG often has a low molecular weight, making it challenging to form into the membrane. The crystalline high average molar mass poly(ethylene oxide) (PEO) cannot exhibit CO separation characteristics. Thus, it is crucial to employ low molecular weight PEG in high molecular weight polymers to increase the CO affinity for CO separation membranes. In this work, poly(acrylic acid) (PAA)/PEG blend membranes with a PEG-rich phase were simply fabricated by physical mixing with an ethanol solvent. The carbonyl group of the PAA and the hydroxyl group of the PEG formed a hydrogen bond. Furthermore, the thermal stability, glass transition temperature, and surface hydrophilicity of PAA/PEG blend membranes with various PEG concentrations were further characterized. The PAA/PEG(1:9) blend membrane exhibited an improved CO permeability of 51 Barrer with high selectivities relative to the other gas species (H, N, and CH; CO/H = 6, CO/N = 63, CO/CH = 21) at 35 °C and 150 psi owing to the enhanced CO affinity with the amorphous PEG-rich phase. These PAA/PEG blend membrane permeation characteristics indicate a promising prospect for CO capture applications.