A single crystal of a tactic polymer can be utilized as a high-performance separation membrane (smart membrane) for separating and recovering a target substance, by controlling the structure of the pore, the so-called a "molecular cavity," between the polymer chains. Although various studies have been carried out to elucidate the structure of the molecular cavity, it is difficult to intuitively understand the complex three-dimensional cavity structure. In this study, for a better understanding of these structures, a three-dimensional model of the cavity was created by using a 3D printer. The molecular cavities of the δe, ε, and S-I form of syndiotactic polystyrene (s-PS) were reproduced by molecular dynamics (MD) simulation. The obtained structural data were converted into 3D printable STL data, and solid models of the molecular cavities were fabricated by the 3D printer. For the δe form, two types of channel structures along the b axis and ac-axis directions were reproduced. The channel along the ac-axis direction, along which the gas molecules are likely to diffuse, was demonstrated to be shorter and thicker than that along the b axis. On the other hand, cylindrical and zigzag channels were obtained for the ε and S-I forms, respectively. An analysis of the system of cavities associated with diffusing gas molecules was carried out by fabricating 3D models at the moment the gas molecule jumps between cavities. The relationship between the crystal structures and the diffusion pattern of gases could be intuitively understood.
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