Effect of polymer architecture on the gas separation performance of PIM-1 membranes

Molecular simulations are used to demonstrate the effects of chain architectures on the gas separation performance of PIM-1 membranes. Four different architectures (linear, H-shape, star, and dendritic) are considered to investigate the transport properties of four industrially relevant gases (CO₂, CH₄, O₂, and N₂). The simulations indicate that it is possible to tune the free volume morphology of PIM-1 membranes by choosing the appropriate architecture. An inverse relationship between the density and fractional free volume was observed as expected, with the highest density and lowest FFV obtained for the dendritic PIM-1. While the linear PIM-1 showed larger pores that enhanced the diffusivity of all small gases, the branched architectures (H-shape, star and dendritic) showed smaller interconnected pores with several bottle-neck morphologies. The observed modifications resulted in significant differences in the diffusivity of mid-range size gas molecules such as N₂, pushing the performance of CO₂/N₂ and O₂/N₂ separation performance beyond the Robeson’s 2008 upper bound.