Effects of pressure and nanoparticle functionality on CO₂-selective nanocomposites derived from crosslinked poly(ethylene glycol)

Purification of H-2 generated from industrial gasification processes requires removal of CO₂ as the permeate from mixed CO₂/H-2 streams to avoid costly H-2 repressurization. Such gas separation can be achieved through the use of reverse-selective polymer membranes that exhibit high CO₂ affinity. In this work, the physical properties of CO₂-selective membranes composed of poly(ethylene glycol) diacrylate (PEGda), as well as PEGda nanocomposites with 10 wt.-% fumed silica (FS), are reported. Two PEGda oligomers differing in chain length and FS nanoparticles varying in surface functionality are exposed to CO₂ at low and high pressures to elucidate the roles of CO₂ pressure, network topology and nanoparticle aggregation on molecular transport and solubility. Results from swelling and sorption kinetics confirm that both penetrant diffusivity and solubility increase with increasing PEGda chain length and decreasing network density. Methacrylate-terminated FS nanoparticles are more effective in improving rheological properties and retaining high CO₂ selectivity than hydroxyl-terminated nanoparticles of comparable size.