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、氢核磁袁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.
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