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 crosslinking 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.