Radical polymerization of N-methyl-N-(2-pyridyl)acrylamide (MPyAAm) was carried out in dichloromethane at low temperatures in the presence of trifluoroacetic acid (TFA). The m dyad contents of the polymers obtained at 0 degrees C increased linearly from 37 to 60% with an increase in the [TFA](0)/[MPyAAm](0) ratio from 1 to 5. Nuclear magnetic resonance (NMR) analysis of MPyAAm-TFA mixtures in dichloromethane-d(2) revealed that the favorable conformation in terms of the pyridyl group to the carbonyl group in MPyAAm switched from s-trans to s-cis by protonation. The results suggest that controlling the conformation of MPyAAm resulted in control of the stereospecificity in radical polymerization of the monomer. (C) 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 49: 4164-4171,2011