聚乳酸-聚乙二醇的熔融共聚及结构表征

Characterization of Poly(L-Lactic Acid)-Polyethylene Glycol Copolymers Synthesized by Melt Copolymerization

从L-乳酸缩聚得到预聚物,系统地研究了数均分子量200～2000的聚乙二醇(PEG)与乳酸预聚物的直接熔融共聚,采用对甲苯磺酸/氯化亚锡/辛酸亚锡三元催化体系,通过乳酸预聚物与PEG熔融共聚,制备了重均分子量均在两万以上、分子量分布较窄的左旋聚乳酸(PLLA)-PEG共聚物。利用傅里叶变换远红外、氢核磁表征证明了共聚产物主要为PLLA-PEG结构;差示扫描量热分析表明,共聚物相比均聚物PLLA,玻璃化转变温度Tg、熔点Tm、结晶度Xc均降低;旋光分析表明,共聚物中L-乳酸的旋光度降低,聚合过程存在一定的消旋化;应力流变仪分析表明共聚物韧性有所提高。

Prepolymers were prepared through a dehydration process from L-lactic acid. Poly（L-lactic acid）- polyethylene glycol（PLLA-PEGs） copolymers were prepared by the direct melt polymerization of prepolymer and polyethylene glycol using TSA/SnC12/Sn（Oct）2 as catalyst. FT-IR and 1H-NMR spectra show that the structures of copolymers are mainly PLLA-PEGs. DSC results show that the glass transition temperature, melting point and crystallinity of the copolymer are lower than those of neat PLLA. The optical rotation of L-lactic acid decreases during the polymerization. The rheological analysis shows that the tenacity of copolymer increases.