中文摘要：

利用有机催化剂——1，8-二氮杂双环[5．4．0]-7-十一碳烯（DBU），以异丙醇为引发剂，实现丙交酯在常温、常压下的活性开环聚合反应，合成可作为医用材料的分子量可控的聚乳酸。反应机理为有机催化剂DBU与引发剂异丙醇通过氢键形成中间体，中间体中呈负电性的氧对丙交酯羰基中的碳进行亲核进攻，使丙交酯单体通过酰氧键断裂，进行开环聚合反应。通过FT-IR和^1H NMR对聚乳酸的结构进行了表征。通过调节丙交酯和异丙醇的摩尔比来调控产品聚乳酸的分子量，GPC分析表明该聚合方法能够实现聚乳酸分子量的有效控制，且聚乳酸分子量分布很窄。通过分析聚合反应时间对聚乳酸产率的影响，确定了poly-lactide-3000、polylactide-5000、polylactide-7000和polylactide—10000的适宜聚合反应时间分别为20、30、40和50min。

英文摘要：

Living ring-opening polymerization of lactide was carried out under normal temperature and pressure by using 1,8-diazabieyclo（5. 4. 0. ）-7-undeeene （DBU） as an organocatalyst and isopropanol as an initiator, the molecular weight controllable polylactide which can be applied to medical materials was successfully synthesized. The reaction mechanism is that an intermediate is formed via hydrogen bond between DBU and isopropanol, the electronegative oxygen of the intermediate has an nucleophilic effect on the carbon of carbonyl group in lactide molecule so that the ring-opening polymerization of lactide is performed through the cracking of acyloxy bond. The polylactide was characterized by FT-IR and ^1 H NMR. The molecular weight of polylaetide was adjusted by adjusting the mol ratio of lactide and isopropanol, GPC analyses indicated that the molecular weight of polylactide could be effectively controlled and narrow polydispersity was obtained. The effects of polymerization time on the yield of polylactide were investigated, the optimum polymerization time of polylactide-3000, polylactide-5000, polylactide-7000 and polylactide-10000 was 20, 30, 40 and 50min, respectively.