Stereospecific radical polymerization of alpha-(alkoxymethyl)acrylates controlled by a catalytic amount of zinc halides

The stereospecific radical polymerization of alpha-(alkoxymethyl)acrylates- benzyl alpha-(methoxymethyl)acrylate, benzyl alpha-(ethoxymethyl)acrylate, and ethyl alpha-(ethoxymethyl)acrylate-in the presence of a catalytic amoun t of zinc halides (ZnCl2 and ZnBr2) was attained, and the obtained polymers had very different tacticities, rich in syndiotacticity (up to r = 0.71), from that prepared in the absence of a zinc salt (atactic). In contrast, no change was observed in the stereoregularity of the polymethacrylates radic ally obtained in the presence of ZnBr2 as an additive. The coordination of zinc salts to polar alpha-substituents on the omega-end of the propagating polymer and the monomer must play an important part in this system.