Modeling gas diffusion and gas storage in amorphous aggregates of large polyconjugated molecules

Abstract

The aggregation of molecules characterized by some degree of rigidity, in amorphous systems, leads to the presence of voids that are responsible for important properties of the amorphous material. One example is the diffusion of small atoms or molecules through polymers or other materials, which is of relevance in the fabrication of materials for packaging, or for efficient gas sensors and biosensors. A second example, is the physisorption of hydrogen molecules in carbonaceous materials, of relevance for the utilization of hydrogen as a pollution-free energy carrier. In this work we present a computational study, carried out with the help of molecular mechanics and molecular dynamics simulations, of the diffusion and storage of gas particles inside samples of amorphous aggregates: in particular we concentrate on the diffusion of He into the branched structure of polypyrrole, and simulate the hydrogen storage capacity of aggregates of three-dimensional polyphenylene dendrimers.