Crystallization of poly(α-methyl-α-N-propyl-β-propiolactones) prepared from homogeneous and heterogeneous initiators

Half-crystallization times t_½, enthalpies of fusion ΔH, melting temperatures T_f glass transition temperatures T_g x-ray patterns, and morphologies were obtained for nine samples of poly(α-methyl-α-n-propyl-β-propiolactones) prepared from different homogeneous or heterogeneous initiators. The bulk of the results indicates that all samples can be classified into two categories: Polymers A having t_½?, 100 min, ΔH ? 26 J/g, T ? 376 K, T_g ? 275 K, and Polymers B having t_½ ? 10 min, ΔH ? 14.5 J/g T ? 425 K and T_g ? 271 K. Polymers A were prepared with homogeneous initiators while polymers B were polymerized with heterogeneous intiators. The difference in crystallization behavior between polymers A and polymers B is certainly due to a difference in microstructure, brought about by the initiators, which has been qualitatively observed by NMR.