Acrylamide polymerization tacticity

One important application of Lewis acid to asymmetric radical reactions is in the control of tacticity in free radical polymerizations. Recently, Porter [38] showed that Sc(OTf)3 modulates the polymerization of oxazolidinone acrylamides to produce highly isotactic copolymers (Scheme 12). The same study described homopolymerizations in which the m/r dyad ratio was dependent on the reaction temperature. 

There arc exceptions to this general rule. For example, polymerizations of methacrylates with very bulky ester substituents (1-4) show a marked preference for isotacticity w hcrcas polymerizations of MMA show a significant preference for syndiotacticity (Table 4.1). Polymerization of the acrylamide derivative 5 which has a bulky substituent on nitrogen also provides a polymer that is highly isotactic. " AM and simple derivatives (NIPAM, DMAM) give polymers that are slightly syndiotactic (Table 4.1). Tacticity can be influenced by solvent and... 

The polymerization of optically active acetals and vinyl acrylamides has been described but only in a few cases. Poly-[(-)-7V-propyl-7V-phenylethyl-acrylamide] and poly-[(+)-A -methyl-A -phenyl-ethyl-acrylamide] (VIII) of different tacticity were prepared by Schultz and Kaiser [18] from the corresponding monomers using radical or ionic initiators. No assumptions on polymer conformation in solution have been made. 

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