Metal-free isotactic-specific radical polymerization of N-alkylacrylamides with 3,5-dimethylpyridine N-oxide: The effect of the N-substituent and solvent on the isotactic specificity

Radical polymerization of N-methylacrylamide (NMAAm), N-n-propylacrylamide, N-isopropylacrylamide (NIPAAm) and N-benzylacrylamide was investigated in CHCl3, CH2Cl2 and CH3CN, in the presence of 3,5-dimethylpyridine N-oxide (35DMPNO) to examine the effects of the N-substituent and the solvent on the isotactic specificity induced by 35DMPNO. With addition of 35DMPNO to radical polymerization of N-alkylacrylamides in CHCl3, isotactic specificity was significantly induced in NIPAAm polymerization but only slightly induced in NMAAm polymerization. Furthermore, mixed solvents of CH3CN and halomethanes such as CHCl3 and CH2Cl2 enhanced the ability of 35DMPNO to induce isotactic specificity, and poly(NIPAAm) with 74% meso dyad was obtained.