Microporous glassy polymers are promising materials for gas separation membranes due to their high permeability and tailorable selectivity. However, physical aging—characterized by a decrease in free volume—compromises their large-scale applications. Our prior experimental results suggest that blending the microporous glassy polymer PTMSP with a hyper-crosslinked isatin-triptycene porous polymer network (PPN) reduces the extent of physical aging, although it affects the permeability of light gases. To identify the molecular mechanisms responsible for physical aging and selective permeability, and how they are connected, we have used molecular dynamics simulations. The atomistic models satisfactorily reproduce experimental data such as matrix density and cavity size distributions and provide additional insights concerning connectivity and PPN distribution throughout the PTMSP matrix. The atomistic models are then used to probe transport mechanisms and solubility for light gases such as CH4 and CO2. The results show that different gases travel across the polymer matrix following preferential pathways governed by molecular interactions. Consistent with macroscopic experimental observations, this microscopic understanding can help engineer future polymeric materials with high permeability and selectivity coupled with slow aging.
