聚己内酯对左旋聚乳酸结晶行为的影响

Effect of Poly(ε-caprolactone) on the Crystallization Behavior of Poly(L-lactic acid)

采用端羟基聚己内酯(PCL)并控制丙交酯(L-LA)的质量合成不同嵌段长度的PLLA-PCL-PLLA三嵌段共聚物;使用相对分子质量相近的左旋聚乳酸(PLLA)与PCL均聚物共混得到PLLA/PCL共混物。红外光谱测试和核磁共振氢谱测试确定了共聚物结构。差示扫描量热(DSC)测试结果表明,PCL的引入有效提高了PLLA嵌段共聚物和PLLA均聚物的结晶速率。利用DSC考察总结晶速率,热台偏光显微镜考察生长速率,结果表明当共聚物中PLLA嵌段相对分子质量与共混物中PLLA均聚物相对分子质量相当时,PLLA嵌段与PLLA均聚物结晶速率相当。PCL的加入使得PLLA最大结晶速率所对应的温度降低,其加入方式对PLLA的结晶形貌有一定的影响,无论以共聚或共混的方式引入PCL均对PLLA结晶速率的提高有积极作用。

A series of PLLA-PCL-PLLA copolymers with different poly(L-lactic acid)(PLLA) lengths were synthesized by the ring-opening polymerization, PLLA/PCL blends were prepared by blending PLLA and poly(ε-caprolactone)(PCL) with similar molecular weight. The structures of PLLA-PCL-PLLAs were confirmed by Fourier transform infrared spectroscopy(FT-IR)and ^1H-NMR spectroscopy. Different scanning calorimetry (DSC) results show that the introduction of PCL can effectively promote the crystallization rate of PLLA. Based on the observations of total crystallization rate by DSC and the growth rate of spherulites by polarizing microscope (POM), it can be found that when the PLLA block in PLLA-PCL-PLLA copolymers has an equivalent molecular weight with PLLA homopolymer in PLLA/PCL blends, PLLA block and PLLA homopolymer in PLLA/PCL blends have an equivalent crystallization rate, and it is higher than that of the PLLA neat homopolymer. It indicates that the introduction of PCL reduces the crystallization temperature of PLLA corresponding to its maximum crystallization rate, meanwhile, the crystallization morphology of PLLA is also affected by the way PCL incorporated. The result shows that by both the copolymerization and the blending routes, the crystallization behavior of PLLA can be improved with a similar positive effect.