乳酸-乙醇酸共聚物的制备及降解性能研究

Preparation and degradation behavior of high molecular weight poly(L-lactic-co-glycolic acid)

以L-乳酸(L-LA)和乙醇酸(GA)为原料(L-LA和GA投料摩尔比为80∶20),二水合氯化亚锡和对甲苯磺酸(TSA)为复合催化剂,采用直接熔融缩聚法制OLGA预聚物,然后在扩链剂六亚甲基二异氰酸酯(HDI)存在下进行熔融扩链,最终得到较高分子量的乳酸-乙醇酸共聚物(PLGA),其数均分子量和重均分子量分别为5.5×104和1.3×105。将溶液浇铸法制备的PLGA薄膜在37℃、pH=7.3～7.4的磷酸盐缓冲液(PBS)中进行降解实验,采用pH分析、失重率测量、GPC、SEM、FT-IR等方法研究了PLGA薄膜的降解行为,并对降解机理进行了初步探讨。结果表明,随着降解的进行,PLGA薄膜的相对分子量和质量都会逐渐下降,在降解反应进行的前21天中,相对分子量的减小较明显,21天之后质量损失较明显。结合FT-IR谱图的研究,分析可知PLGA的降解主要是通过酯键的水解实现的。

A low molecular weight pre-polyrner （OLGA）, consisting of L-lactic acid （L-LA） and glycolic acid （GA） （L-LA/GA=80/20,molar ratio）,were prepared via melt polycondensation using SnCl2·2H2O and TSA as the catalysts. Poly（lactic-co-glycolic） copolymer （PLGA） with Mn of 5.5×104 and Mw of 1.3×105 has been successfully synthesized via chain-extension reaction of OLGA using aliphatic 1,6-hexamethylene diisocyanate （HDI） as the chain extender. The degra- dation behavior of PLGA in phosphate buffer solution（PBS） at 37℃ was investigated by potentiometry, gravimetry, GPC, SEM and FTIR. The results showed that the molecular weight and the mass of PLGA films were gradually decreased with the increase of degradation time. The degradation process was divided into two main steps. In the first period from 0 to 21 days, the molecular weight of PLGA decreased obviously. Subsequently the main degradation process was the mass loss and the releasing of acids. The FITR results suggested that the degradation of PLGA was mainly from the hydrolysis of the ester bond.