Radical polymerization behavior of N,N-disubstituted acrylamide: Absolute rate constants for polymerization and copolymerization of N-acryloylpiperidine

The absolute rate constants of propagation (k_p) and of termination (k_t) of N-acryloylpiperidine (NAPi) were determined by the rotating sector method in bulk; k_p = 273 and k_t = 1.79 × 10⁷ L/mol s at 30°C. It was noted that k_p for NAPi was 100 times smaller than that for N,N-dimethylacrylamide (DMAcAm). The absolute rate constants of cross-propagations for copolymerizations with common monomers were evaluated by combination of the k_p value and the monomer reactivity ratios. Quantitative comparison of the rate constants with those of DMAcAm and poly(DMAcAm) radical shows that NAPi is as reactive as DMAcAm and the smaller k_p value for NAPi is ascribable to much the lower reactivity of the poly(NAPi) radical. The large difference in reactivity of the polymer radicals is discussed in relation to the steric factor of the piperadino and the dimethylamino groups which seems to affect the capability of the carboxamide group to stabilize the polymer radical.