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用同核去偶1 HNMR法研究了以异辛酸亚锡为催化剂、 135℃开环聚合而得的低左旋度聚 (L_丙交酯 )(L_PLLA)以及聚 (L_丙交酯 ) (PLLA)和聚 (D ,L_丙交酯 ) (PDLLA)的链结构。结果表明 ,该方法可分辨出分子链中相邻 6个立构单元序列的化学位移 ,并由几个清楚分辨的共振峰获得了聚合物的立构序列分布及原料组成的定量结果。其中PLLA样品是完全左旋等规的 ,L_PLLA次之 ,而PDLLA是完全无规的 ,后二者的序列分布结果表明聚合过程中丙交酯的间规加成所占的比例较大。在本聚合条件下 ,未发现有酯交换和消旋化现象。此外 ,L_PLLA的1 HNMR谱在 5 2 5 1处有一弱小的共振峰 ,该峰在文献中未见报道 ,它的立构序列归属有待进一步研究。
The homocoupled 1 H NMR method was used to study the low L-lactide (L_PLLA) and poly (L-lactide) (L-lactide) PLLA) and poly (D, L-lactide) (PDLLA). The results show that this method can distinguish the chemical shifts of the 6 adjacent building blocks in the molecular chain and obtain the quantitative distribution of the stereospecific structure of the polymer and the quantitative composition of the raw materials by several well-resolved resonances. PLLA samples are completely levorotatory, L_PLLA is the second, and PDLLA is completely random, the latter two sequence distribution results show that the polymerization process lactide the syndiotactic addition accounted for a large proportion. Under the polymerization conditions, no transesterification and racemization were observed. In addition, the 1 HNMR spectrum of L_PLLA has a weak resonance peak at 5 2 5 1, which has not been reported in the literature. Its stereological sequence is for further study.