l-Lactide was polymerized by means of neat SnOct₂ with variation of LA/Cat ratio, temperature and time. The resulting cyclic polylactides crystallized spontaneously at 160 °C or below, but needed nucleation via mechanical stress at 165 or 170 °C. All the crystalline polylactides obtained directly from ROP above 120 °C had melting temperatures (T_m) above 189 °C (up to 194.5 °C). SnOct₂ also enabled transformation of low T_m poly(l-lactide)s (T_m < 180 °C) into the high T_m m¹odification by annealing, due to the impact of transesterification reactions in the interphase between the crystallites. The influence of crystallization temperature and annealing time on the crystal thickness was studied via SAXS measurements. A comparison with the crystallization and annealing experiments reported by Pennings and coworkers and Tsuji and Ikada is discussed, and a satisfactory agreement has been found, because those authors also studied polyLA samples containing SnOct₂ in its active form. It is also demonstrated in this work that the high T_m modification cannot be obtained when the catalyst is removed or poisoned as it is true for commercial polylactides.

l -丙交酯通过纯 SnOct ₂聚合，LA/Cat 比率、温度和时间发生变化。所得环状聚乳酸在 160 °C 或更低温度下自发结晶，但需要在 165 或 170 °C 下通过机械应力成核。在 120 °C 以上直接从 ROP 获得的所有结晶聚交酯的熔化温度 (T _m ) 都高于 189 °C（高达 194.5 °C）。SnOct ₂还使低 T _m聚（l -丙交酯）（T _m  < 180 °C）转变为高 T _m m ¹由于微晶之间的中间相中的酯交换反应的影响，通过退火进行改性。通过 SAXS 测量研究了结晶温度和退火时间对晶体厚度的影响。讨论了与 Pennings 及其同事以及 Tsuji 和 Ikada 报告的结晶和退火实验的比较，并发现了令人满意的一致性，因为这些作者还研究了含有活性形式SnOct _{2 的}聚LA 样品。在这项工作中还证明，当催化剂被去除或中毒时，无法获得高 T _m改性，这对于商业聚交酯来说是正确的。