Stereospecific preparation of polyacrylamide with low polydispersity by ATRP in the presence of Lewis acid

The stereospecific atom transfer radical polymerizations of acrylamide were achieved in the presence of the Lewis acid Y(OTf)3 or AlCl3 as stereospecific catalyst using chloroacetic acid/CuCl/N,N,N′,N′-tetramethyl-ethylenediamine (TMEDA) as initiating system. The addition of Lewis acid Y(OTf)3 in the ATRP of acrylamide led to an increased polymerization rate and an improved tacticity of polyacrylamide (m ∼ 71%) at the expense of controllability of the molecular weight distribution. In the case of AlCl3, the polymerizations were committed to afford the resultant polyacrylamide with lower polydispersity index ranging from 1.03 to 1.42 and well-controlled tacticity with meso content ranging from 57 to 76% depending on the different reaction conditions used. Lower temperature or higher concentration of the feeding Lewis acid helped to obtain the polyacrylamide with increased tacticity which revealed a decreased glass transition temperature (Tg).