Crystal structure of syndiotactic polypropylene

Double oriented fiber spectra of syndiotactic polypropylene were obtained. It was possible to redetermine with greater accuracy the unit cell constants, which are: a = 14.50, b = 5.60, c = 7.40 A. Space group: C2221. It was proved that the chain has s(2/1)2 symmetry, corresponding to a succession of internal rotation angles A2B2A2B2. The agreement between experimental and calculated intensities on the hkl layers with l = 0, 1, 2, 3 up to the lowest observed Bragg distance (about 2 A.) is good for the packing model proposed. The structural results are briefly discussed.