中文摘要：

以三羟甲基乙烷为起始剂,开环聚合L-丙交酯（LLA）,合成三臂支化左旋聚乳酸（PLLA）预聚物.采用端基活化技术对预聚物进行端羟基活化,再与D-丙交酯（DLA）进行开环聚合,合成了不同分子量的三臂支化左旋聚乳酸-右旋聚乳酸（PLLA-PDLA）嵌段共聚物.采用核磁共振谱和凝胶渗透色谱等对样品的结构和分子量进行测试,结果表明,合成的嵌段共聚物链结构具有链段立构规整度和高分子量的特点;通过调节DLA单体与PLLA预聚物的投料比,可实现对PLLA-PDLA嵌段共聚物的序列结构调控.差示扫描量热仪和广角X射线衍射结果表明,三臂支化PLLA-PDLA嵌段共聚物的异构体分子间生成立构复合晶体,其熔点高于200℃;共聚物的嵌段序列结构对材料的凝聚态转变行为有很大的影响.

英文摘要：

The tri-arm poly （L-lactide） was prepared by ring-opening polymerization （ROP） of L-lactide （LLA） with 1,1,1-tris （hydroxymethyl） ethane （TME） as an initiator. The terminal hydroxyls of the pre-polymer were activated by stannous oetanoate[ Sn（ Oct）2 ]. Then a series of novel tri-arm poly（L-lactide）-poly（ D- lactide ） （PLLA-PDLA） block copolymers were synthesized by ROP of D-lactide （DLA） with functioned PLLA- SnOct pre-polymer as a macroinitiator. Nuclear magnetic resonance spectroscopy （NMR） and gel permeation chromatography（ GPC ） results confirmed the configuration of the tri-arm PLLA-PDLA block copolymers with high isotacticity and high molecular weight. The block structure of copolymer could be readily adjusted in terms of the feed ratio of monomer with the PLLA pre-polymer. Differential scanning calorimetry （ DSC ） and wide-angle X-ray diffraction （WAXD） demonstrated that the stereocomplex PLA （Sc-PLA） were formed be- tween intramolecular and intermoleeular PLLA and PDLA blocks. The melting temperature （ Tm ） of Sc-PLA crystals was above 200 °C, which was much higher than that of pure PLLA. These results show that a novel tri-arm PLLA-PDLA block copolymer would be promising as a heat-resistant PLA engineering material.