Stereoregularity of polystyrene derivatives, 1. Poly(methylstyrene)s and poly(methoxystyrene)s obtained with ziegler catalyst,cationic catalyst,or radical initiators

The ¹³C NMR spectra of methylstyrenes and methoxystyrenes and their polymers prepared with radical initiators, a Ziegler catalyst, or a cationic catalyst were measured. The spectra of the polymers were assigned by the chemical shifts of the monomers and gated-decoupling method. The absorption of the aromatic C¹ carbon of each polymer, which varied by the polymerization conditions, was assigned in terms of a pentad sequence assuming that the Bernoullian statistics holds for the polymerization of ring substituted styrenes. The stereoregularities calculated from C¹ carbon absorptions were compared with those of polystyrenes obtained unter the same polymerization conditions. In the radical polymerization of ortho-derivatives, where the substituent locates near the polymer backbone, high syndiotactic polymers (P_r = 0,80 ? 0,83) were prepared. The effect of the substituent in para-derivatives did not appear. On the other hand, random polymers were generally fromed by cationic polymerization regardless of the position and the type of the substituent.