An intercalate molecular complex of syndiotactic polystyrene

The crystal structure of the molecular complex of syndiotactic polystyrene (s-PS) with bicyclo[2.2. 1]hepta-2,5-diene (norbornadiene, NB) is presented. In analogy to the already described s-PS molecular complexes, this structure presents a monoclinic unit cell (cell constants a = 17.5 angstrom, b = 14.5 angstrom, c = 7.8 angstrom, and gamma = 107.8 degrees) in which the s(2/1)2 polymer helices and guest molecules are packed according to the space group P2(1)/a. However, the structure of the s-PS/NB complex presents layers of contiguous guest molecules alternated with layers of enantiomorphous polymer helices and hence can be described as an intercalate phase. On the other hand, all the known structures of other s-PS molecular complexes present isolated molecules (or a couple of small molecules) into the cavities typical of the nanoporous s-PS delta form and hence can be described as clathrate phases. The molar ratio between the monomeric unit and the guest is 2/1 for the s-PS/NB intercalate phase, while it is generally 4/1 for the s-PS clathrate phases.