Polymers of intrinsic microporosity (PIMs) are a new class of porous polymer based on the simple design principle of combining monomers that are both rigid and non-planar or non-linear . These structural conditions inhibit space efficient packing and give the polymers their microporosity, but put no limitation on the chemical structure of the monomers. The potential for a wide variety of chemistries combined with the high surface areas make PIMs a novel material to address a variety of issues such as gas storage, separations, purification, and catalysis. To date, a variety of PIMs have been synthesized in both networked and non networked forms. The aim of this research is to develop a thorough understanding of the adsorption process in PIMs, by comparing the physical characteristics and adsorption behavior of a family of related non-networked PIMs based on the PIM-1 structure. PIM-1 consists of a backbone of fused aromatic rings and a spirobisindane which adds the non-linear site of contortion. By substituting the backbone nitrile functional groups with fluorine or an aromatic nitrogen, the so called KJM 98, 99, and 100 set of PIMs have been synthesized. Likewise, by adjusting the spirocenter functional groups to carbonyl oxygens, PIM-1c is obtained . Recently we had studied PIM-1 by both molecular simulations and experiments . Here, we characterized by molecular simulations KJM 98 and PIM-1c. First, we carefully parameterize the polymers using ab initio methods to determine the charge distribution using the HF/6-31G* basis set. Second, a molecular dynamics relaxation process is used  to develop highly realistic simulation samples of each PIM. Third, all samples are characterized by surface areas and pore size distributions which highlight the structural differences produced by each functional modification. Finally, the adsorptive behavior of each PIM sample is predicted by grand canonical Monte Carlo adsorption simulations of methane and several other gases. These predictions are expected to guide future experimental work, and thus aid in the rational design of novel PIMs for use in adsorptive storage and separations technology.
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