Stereospecific Anionic Polymerization of N,N-Dialkylacrylamides

N,N -Dimethylacrylamide (DMA), N,N -diethylacrylamide (DEA), N,N -dipropylacrylamide (DPA), N- ethylmethylacrylamide (EMA), N- acryloylpyrrolidine (APY), N- acryloylpiperidine (API), and N -acryloylmorpholine (AMO) were polymerized with 1,1-bis[(4‘-trimethylsilyl)phenyl]-3-methylpentyllithium ( 1 ) and with 1,1-bis[(4‘-trimethylsilyl)phenyl]-3,3-diphenylpropylpotassium ( 2 ) in THF in the presence of additives. Although the polymers produced directly with 1 or 2 have broad molecular weight distributions, the addition of Et 2 Zn to the polymerization systems leads to slow propagation reaction and narrow molecular weight distributions of the polymers. The poly( N,N -dialkylacrylamides) produced with 1 are rich in isotactic configuration, while the addition of Et 2 Zn reduces isotacticity and increases the degree of syndio- and heterotacticity. In particular, the poly(DEA)s generated with 1 /Et 2 Zn and 1 /LiCl are highly syndiotactic and isotactic, respectively. Although the broad distributions of triad sequence are observed for the polymers produced with 2, the highly heterotactic poly(DEA) is formed with 2 /Et 2 Zn at 0 °C. The additive effects of Et 2 Zn on the molecular weight and tacticity are supposed to be caused by the coordination of Et 2 Zn with the propagating enolate anion.