COMPUTATIONAL STUDY OF FLUORINATED POLYMER OF INTRINSIC MICROPOROSITY PIM-2 WITH EXPERIMENTAL DATA COMPARISON

A new synthesis technique1 has led to the formation of self-standing films of the linear polymer synthesized from commercially available 5,5?,6,6?- tetrahydroxy-3,3,3?,3?-tetramethylspirobisindane (TTSBI) and decafluorobiphenyl (DFBP) monomers, PIM-2, bringing new interest in this material. A computational study was performed in order to understand the gas transport proprieties of this polymer, belonging to the promising class of polymer of intrinsic microporosity (PIM) and results were compared with the experimental analysis2. It was found a high fractional free volume (FFV) of about 34% and a Brumauer-Emmett-Teller (BET) surface area of 642 m2g-1, in agreement with experimental value of 636 m2g- 1. The low BET surface area and the high FFV, thus the low interconnectivity, is responsible for the about average permeability performance, that sees CO2 being the most permeable gas and N2 the least permeable gas. Sorption isotherms show dual-mode behaviour for all gasses, except for H2 that follows Henry's law. Solubility coefficients decrease as a function of gas critical temperature. Polymer chains appear not to have particular interaction with gas molecules, but to from inter- and intra-chains halogen and hydrogen bonds. References 1. Sato H. et al., React. Funct. Polym., 125, 70-76, 2018. 2. Fuoco A. et al., Journal of Membrane Science, 594, 117460, 2020.