Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455-0431, USA.
Biomacromolecules. 2009 Oct 12;10(10):2904-11. doi: 10.1021/bm900721p.
A series of polylactide-polymenthide-polylactide triblock copolymers containing either amorphous poly(D,L-lactide) or semicrystalline, enantiopure poly(L-lactide) or poly(D-lactide) end segments were synthesized. Small-angle X-ray scattering and differential scanning calorimetry data were consistent with microphase separation of these materials. The Young's moduli and ultimate tensile strengths of the semicrystalline triblock copolymers were 2- and 3-fold greater, respectively, than their amorphous analogs. Symmetric (50:50) and asymmetric (95:5) blends of the triblock copolymers containing two different enantomeric forms of the polylactide segments formed stereocomplex crystallites, as revealed by wide-angle X-ray scattering and differential scanning calorimetry. Compared to the enantiopure analogs, these blends exhibited similar ultimate elongations and tensile strengths, but significantly increased Young's moduli. Collectively, these results demonstrate that the properties of these new biorenewable thermoplastic elastomers can be systematically modulated by changing the stereochemistry of the polylactide end blocks.
一系列含有无定形聚（D，L-丙交酯）或半结晶、手性纯聚（L-丙交酯）或聚（D-丙交酯）末端段的聚乳酸-聚乙交酯-聚乳酸三嵌段共聚物被合成。小角 X 射线散射和差示扫描量热法数据与这些材料的微相分离一致。半结晶嵌段共聚物的杨氏模量和极限拉伸强度分别比其无定形类似物高 2 倍和 3 倍。含有两种不同手性形式的聚乳酸段的嵌段共聚物的对称（50:50）和不对称（95:5）共混物形成了立构复合晶体，这可以通过广角 X 射线散射和差示扫描量热法揭示。与手性纯类似物相比，这些共混物表现出相似的极限伸长率和拉伸强度，但杨氏模量显著增加。总的来说，这些结果表明，这些新型生物可再生热塑性弹性体的性能可以通过改变聚乳酸末端块的立体化学来系统地调节。
