A series of novel N-substituted-N-vinylformamides were synthesized, and the effect of bulky substituents on their radical polymerizability and polymer structure were investigated. N-(p-Methoxybenzyl)-N-vinylformamide (3) and N-cyclohexylmethyl-N-vinylformamide (4) generated polymers, while it was known that their N-vinylacetamide derivatives did not. (1)H NMR and (13)C NMR analyses of poly(3), however, revealed almost no difference among the various polymerization conditions, implying that the substituent bulkiness did not influence the polymer structures. On the other hand, the chiral polymers, which were obtained by the radical polymerization of N-(S)-2-methylbutyl-N-vinylformamide ((S)-5) and N-(S)-2,3-dihydroxy-propyl-N-vinylformamide ((S)-7) at 0 degrees C, showed sharper spectral patterns than those obtained at higher polymerization temperatures. Furthermore, the intensities of their positive cotton effects on circular dichroism increased when the polymerization temperature was low, suggesting that the substituent bulkiness of (S)-5 and (S)-7 influenced the polymer structures, such as their stereoregularity and regioregularity. (C) 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 50: 134-141, 2012