【摘要】 以辛酸亚锡为催化剂,135℃下低左旋度的l-丙交酯([a]_Na²⁵=—231°)开环聚合制备了低左旋度聚（l-丙交酯）[l-PLLA]([a]_CHCl3²⁵=-119.7°),并用同核去偶¹H-NMR谱表征其分子链结构。用成纤模压法制备了该聚合物的棒材（φ=3.2mm）试样,研究了其在37℃的模拟体液（SBF）中的降解行为。结果表明,l-PLLA具有良好的力学性能,其初始弯曲强度（σ_b）、剪切强度（σ_s）以及弯曲模量（E_b）虽比聚（l-丙交酯）（PLLA）低,但均比聚（dl-丙交酯）（PDLLA）高得多,且材料表现出很好的韧性,呈非晶态,其分子量下降速率和失重速率都介于PLLA和PDLLA之间,可望是一种良好的骨折内固定材料。更多还原

【Abstract】 A low optical activity poly( l -lactide) ( l -PLLA) was synthesized by ring-opening polymerization of low optical l-lactide at 135 ℃ using Sn(Ⅱ) octoate as catalyst. Its chain structure was characterized by homonuclear decoupled 1H- NMR of methine. The degradation behavior in the simulation body fluid(SBF) at 37 ℃ show that the initial bending strength, bending modulus and shear strength of the l -PLLA are lower than those of poly( l -lactide) (PLLA) , but much higher than those of poly( dl -lactide) (PDLLA), even if its initial molecular weight is much smaller than the latter. The variation of bending stress and shear stress with strain for the l -PLLA indicates that it has a better tenacity than PLLA and PDLLA. The changes in mechanical properties with degradation time for the l -PLLA are similar to PDLLA. After degradation for 8 weeks, the l -PLLA still has the initial mechanical properties of PDLLA. This is favorable to the situations of requiring higher mechanical properties at the early stage for internal fixation and better maintenance in morphology for tissue engineering. The molecular weight of the PDLLA dropped down dramatically at the early stage and then decreased more slowly. On the other hand, the molecular weight decreased gently with increasing degradation time for the PLLA and the l -PLLA. The decreasing rate of weight loss of l -PLLA is lower than that of PDLLA, but much higher than PLLA. The results indicate that the chain structure with higher tacticity is favourable to improving the mechanical properties of polymer materials, but slows down the decreasing rates of molecular weight and weight loss during the period of degradation.更多还原