(376q) Structure and Gas Transport Properties of Organic Mixed Matrices: Polymers of Intrinsic Microporosity with Organic Molecules of Intrinsic Microporosity

Polymers of intrinsic microporosity (PIMs) are microporous materials that have attracted attention for their superior solution processability and microporosity, extremely high free volume and surface areas, which make them good candidates for industrial gas storage and separation. However, the physical aging of PIM membranes can lead to a significant reduction in permeability, solubility, and diffusivity over time. Mixed matrix membranes, by incorporation of an inorganic, metal-organic or organic filler into PIM based polymer matrices, have the potential to improve selectivity and reduce aging effect while maintaining permeability. One of the potential organic filler is the large, rigid organic molecules of intrinsic microporosity (OMIMs) which are known to form porous materials due to their inability to pack efficiently in the solid state.

In the present work, organic mixed matrices (MMs) obtained by the addition of different types of OMIMs into PIM-1 were investigated using atomistic molecular simulations. The structure generation of amorphous Organic MMs was achieved by a simulated polymerization algorithm implemented in the open-source software PySIMM and Polymatic. Structural analysis of six different PIM-1/OMIM mixed matrices, with filler wt% in the range of 7-13%, indicated that using OMIMs as fillers can maintain or even increase the free volume and surface area of the organic MM compared to pure PIM-1. Moreover, pore size distributions of the PIM-1/OMIM MM showed the formation of larger pores with OMIMs frustrating the packing. To compare the gas transport properties of these organic MMs with pure PIM-1, grand canonical Monte Carlo was used to obtain the adsorption isotherms of CO₂, N₂, O₂, and CH₄ in these materials. Plasticization behavior of one of the PIM-1/OMIM mixed matrices was also studied using a combined Monte Carlo and molecular dynamics simulation.