Synthesis and degradation of end-group-functionalized polylactide

Three kinds of OH-terminated polylactides were synthesized by the ring-opening polymerization of lactide, with an alcohol such as dodecanol, glycerol, or pentaerythritol, in the presence of stannous octoate. Moreover, Cl-, NH₂-, and COOH-terminated polylactides were synthesized from OH-terminated polylactides. The end groups of the polylactides were identified by ¹H NMR and ¹⁸C NMR. According to thermal analysis, the cold crystallization temperatures of Cl-, NH₂-, and COOH-terminated polylactides were higher than those of OH-terminated polylactides. The thermal stability of OH-terminated polylactides was poor, whereas NH₂- and Cl-terminated polylactides were more resistant to thermal degradation. In a hydrolysis degradation test, the mass and molecular weight loss of COOH-terminated polylactides were high, whereas those of Cl- and NH₂-terminated polylactides were much lower. These end-group effects were increased with an increasing number of chain arms.