Atomistic Structure Generation and Gas Adsorption Simulations of Microporous Polymer Networks

A new general procedure for generating structures for atomistic simulations of network polymers is presented. In the presented algorithm, cross-linking and chain formation occur in cycles along with equilibrations to “polymerize” microporous polymer networks. The procedure was validated by application to a hyper-cross-linked polymer, poly(dichloroxylene), but can be applied to other polymer networks as well. The simulated samples were characterized by cross-linking degrees and porosity measurements, and their adsorption behavior was simulated by grand canonical Monte Carlo (GCMC) simulations. Two important factors in generating samples with significant microporosity were determined: (a) the degree of cross-linking and (b) the concentration of the system during cross-linking. The effects of these two factors were examined and compared to similarly observed experimental trends. The methodology presented here is thus a promising technique for designing not only hyper-cross-linked polymers but also new amorphous, microporous polymers in general.