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.