Gas sorption and diffusion in poly(dimethylsiloxane) (PDMS)/graphene oxide (GO) nanocomposite membranes

Gas solubility and diffusivity are reported for a series of poly(dimethylsiloxane) (PDMS)/graphene oxide (GO) nanocomposites. The nanocomposites were prepared via a crosslinking reaction between the amino-terminal end groups of the telechelic PDMS and epoxide groups on the surface of GO. Gas solubilities of N₂, O₂, CH₄, and CO₂ were measured at 35 °C over a range of pressures. Gas solubility in the nanocomposites was unaffected by GO at the maximum loading of 8 wt%. Therefore, a previously reported decrease in the nanocomposite permeability with increasing GO content was due to a reduction in diffusivity. The pure-gas selectivity of the nanocomposite was controlled by diffusivity selectivity, and both increased with increasing GO content. Based on Meares’ formula, correlations between diffusivity and the square of the kinetic diameter were observed for the nanocomposites. The slopes of these correlations increased progressively as a function of GO content, indicating the enhanced size-sieving ability of the nanocomposites.