投料比对丙氨酸直接熔融聚合法改性聚乳酸的影响

Influences of Feed Ratio on the Biodegradable Material Polylactic Acid Modified by L-alanine via Direct Melt Copolymerization

以L-丙氨酸(L-Ala)为单体,与外消旋乳酸(D,L-LA)直接熔融聚合,合成氨基酸改性的聚乳酸类生物降解材料,并用特性粘数、FTIR、1HNMR、GPC、DSC、XRD等手段进行了表征。随着投料比中丙氨酸含量n(Ala)的增加,改性聚乳酸在氯仿、四氢呋喃等有机溶剂中的溶解性逐渐由易溶变为难溶,但在DMSO中的溶解性却很好;DSC、XRD等测试显示,聚合物由一定的结晶性逐渐转变为无定形态;可溶性共聚物聚(乳酸-丙氨酸)[P(LA-co-Ala)]的特性粘数逐步减小,重均相对分子质量(Mw)逐渐减小,分散度(Mw/Mn)有变窄的趋势。

Using lactic acid（LA） and alanine（Ala） as monomers, biodegradable material polylactic acid modi- fied by amino acid is synthesized via direct melt copolycondensation. The copolymers are characterized by intrinsic viscosity, FTIR, ^1H NMR, GPC, DSC and XRD. The results show that, the more the feed molar ratio of Ala, the worse the solubility in chloroform and tetrahydrofuran（THF）, but the modified polylactic acid is very easily soluble in DMSO. And the results of DSC and XRD show that the crystallinity of copolymer gradually disappears with the decrease of the feed molar ratio of LA. For the soluble copolymer poly（lactic acid-co-alanine） [-P（LA-co-Ala）], with the increase of the feed molar ratio of Ala, its intrinsic viscosity and weight-average molecular weight （Mw） decreased gradually, and its dispersivity （Mw/Mn） becomes narrower.