Summary: The crystal structure of the clathrate form of syndiotactic polystyrene containing different amounts of CS2 has been analyzed, and compared with that of the clathrate containing I2. These two guest molecules, which are characterized by a similar shape and volume, give rise to the only two known examples of clathrate forms containing up to two molecules per cavity. The two structures are isomorphous both in the case of complete and of partial occupation of the cavities. In the second case, CS2 and I2 molecules when alone in the cavity occupy almost identical positions at its center. Some of the literature on the crystal structure of these two clathrates is ambiguous and this is discussed. A comparison with the CS2 clathrates of syndiotactic poly(p-methylstyrene) and poly(m-methylstyrene) is also made.
Schematic representation of the two ways in which guest molecules can be hosted in the cavities of the crystals of the s-PS clathrate form containing carbon disulfide.