Cyclopolymerization. VI. Polymerization mechanism of N-methyl-N-allylmethacrylamide at lower temperature

Mechanistic investigations on the polymerization of N-methyl-N-allylmethacrylamide (MAMA) at lower temperature were carried out based upon the ESR studies of MAMA and its monofunctional counterparts irradiated with ⁶⁰Co γ rays. Cyclopolymerizability of MAMA was also studied in connection with the hindered rotation about its amide C? N bond. The propagating radical observed is only related to the methacryl group but not to the allyl group both in MAMA and its monofunctional counterparts. Polymerization at ?78°C yielded a polymer with a lower degree of cyclization(88.8%) as compared with that of polymers formed at higher temperatures (93.5% above 0°C). A structural study revealed that the increment of the unsaturation in the poly-MAMA obtained at ?78°C is due to the allyl group and the content of pendant methacryl group is almost unchanged over the temperature range from ?78 to 120°C. These results led to the conclusion that the polymerization of MAMA at ?78°C proceeds mainly through the methacryl group, the rate-determining step is the cyclization reaction, and, in addition, cyclization reaction scarcely occurs when it polymerizes through the allyl group. Since MAMA is frozen into a glassy state, the effect of glass transition temperature (T_g) has been studied and it was suggested that the polymerization of MAMA proceeds only above T_g.