The variation in the kinetics of group-transfer polymn. of Me methacrylate [80-62-6] and in the mol. wt. of the resulting PMMA [9011-14-7] with the relative amts. of trimethylsilyl cyanide [7677-24-9] and tris(dimethylamino)sulfonium difluorotrimethylsilicate [59218-87-0] initiators verified previous proposals that this type of polymn. behaved like a living polymn. under certain conditions, with the importance of termination reaction varying with the conditions. 1H NMR measurements indicated that the polymers contained syndiotactic sequences .apprx.58, heterotactic sequences 37, and isotactic sequences 5%.