三臂PPO-PDLA-PLLA 嵌段共聚物的制备与结构及其立构复合体的结晶行为

以环氧丙烷聚醚三元醇(PPO)为起始剂, 开环聚合D 型丙交酯(DLA), 合成三臂环氧丙烷聚醚三元醇-聚右旋乳酸(PPO-PDLA)嵌段预聚体. 采用端基活化技术对预聚体进行端羟基活化, 再与L 型丙交酯(LLA)进行逐步开环聚合,合成了不同分子量的三臂环氧丙烷聚醚三元醇-聚右旋乳酸-聚左旋乳酸(PPO-PDLA-PLLA)嵌段共聚物. 采用红外(FTIR)、核磁(NMR)和凝胶渗透色谱(GPC)等对三臂PPO-PDLA-PLLA 嵌段共聚物的测试表明, 合成的嵌段共聚物分子链具有很高的立构规整度; 通过调节LLA 单体与PPO-PDLA 预聚体的投料比, 不仅可控制产物的分子序列结构, 而且样品的数均分子量可大于100 kDa. 差示扫描量热仪(DSC)和广角X 射线衍射(WAXD)结果显示, 三臂PPO-PDLAPLLA嵌段共聚物的异构体链段分子间生成立构复合晶体, 其熔点约为200 ℃, 且没有PLLA 均聚物链段结晶现象. 实验结果表明, 这是一类具有实际应用价值的新型耐热聚乳酸(PLA)材料.

Synthesis, Structures and Characterization of Triarm PPO-PDLA- PLLA Block Copolymers and Its Stereocomplex Crystallization Behavior

The triarm poly(propylene oxide)-poly(D-lactide)(PPO-PDLA) copolymer was prepared by ring-opening polymerization(ROP) of D-lactide(DLA) with low unsaturated poly(propylene oxide) triols(PPO) as an initiator.The terminal hydroxyls of the prepolymer were activated by stannous octanoate Sn(Oct)2].Then a series of novel triarm poly(propylene oxide)-poly(D-lactide)-poly(L-lactide)(PPO-PDLA-PLLA) block copolymers were synthesized by ROP of L-lactide(LLA) with functioned PPO-PDLA prepolymer as a macroinitiator.Fourier transform infrared(FTIR),nuclear magnetic resonance spectroscopy(NMR) and gel permeation chromatography(GPC) results confirmed the configuration of triarm PPO-PDLA-PLLA block copolymers with high isotacticity,and the number average molecular weight of the samples could be greater than 100 kDa.The block structure of copolymer chain could be readily adjusted in terms of LLA units and molecular weight of PPO-PDLA prepolymer.Differential scanning calo-rimetry(DSC)and wide-angle X-ray diffraction(WAXD)demonstrated that the stereocomplex PLAs(sc-PLAs)were formed between intermolecular PLLA and PDLA blocks without PLLA crystallization process.The melting temperature(Tm)of sc-PLA crystal was about 200℃,which was much higher than that of pure PLLA.These results show that the triarm PPO-PDLA-PLLA block copolymers could be promising as a heat-resistant poly(lactic acid)(PLA)material.