A Molecular Dynamics Study of Single-Gas and Mixed-Gas N and CH Transport in Triptycene-Based Polyimide Membranes.

Fluorinated polyimides incorporated with triptycene units have gained growing attention over the last decade since they present potentially interesting selectivities and a higher free volume with respect to their triptycene-free counterparts. This work examines the transport of single-gas and mixed-gas N and CH in the triptycene-based 6FDA-BAPT homopolyimide and in a block 15,000 g mol/15,000 g mol 6FDA-mPDA/BAPT copolyimide by using molecular dynamics (MD) simulations. The void-space analyses reveal that, while the free volume consists of small-to-medium holes in the 6FDA-BAPT homopolyimide, there are more medium-to-large holes in the 6FDA-mPDA/BAPT copolyimide.

Single-gas and mixed-gas permeation of N/CH in thermally-rearranged TR-PBO membranes and their 6FDA-bisAPAF polyimide precursor studied by molecular dynamics simulations.

High-performance polymers with polybenzoxazole (PBO) structures, formed thermal rearrangement (TR) of aromatic polyimide precursors, have been developed for gas separation applications. The present work compares the transport of N and CH in a 6FDA-bisAPAF polyimide precursor and in its TR-PBO derivative using molecular dynamics (MD) simulations. The modelling closely mimicked the experimental approach by transforming a 6FDA-bisAPAF atomistic model into its corresponding TR-PBO structure a specific algorithm.