PDLA-b-PEG-b-PDLA嵌段共聚物的链结构对聚左旋乳酸性能的影响

Effect of Chain Structure of PDLA-b-PEG-b-PDLA Block Copolymers on the Properties of Poly (L-lactic acid)

采用不同聚右旋乳酸(PDLA)分子量的PDLA-b-PEG-b-PDLA嵌段共聚物改性聚左旋乳酸(PLLA),系统探究不同链结构的PDLA-b-PEG-b-PDLA嵌段共聚物对PLLA的热行为、结晶行为和拉伸性能的影响。结果表明,在降温过程中,PDLA_(1k)-PEG_(2k)-PDLA_(1k)嵌段共聚物对PLLA均聚物晶体(α晶)的结晶温度影响较小,PDLA_(5k)-PEG_(2k)-PDLA_(5k)嵌段共聚物使α晶的结晶温度从纯PLLA的96℃提高至130℃。130℃等温结晶结果显示,嵌段共聚物的加入均能降低α晶的结晶时间和球晶尺寸,PDLA_(5k)-PEG_(2k)-PDLA_(5k)共聚物对PLLA中α晶形成的促进作用明显优于PDLA_(1k)-PEG_(2k)-PDLA_(1k)共聚物。在室温下拉伸,随着PDLA_(1k)-PEG_(2k)-PDLA_(1k)含量提高,共混物由脆性向韧性断裂转变;而在实验比例范围内,PLLA/PDLA_(5k)-PEG_(2k)-PDLA_(5k)共混物均呈现脆性断裂,这与PLLA/PDLA_(5k)-PEG_(2k)-PDLA_(5k)共混物中含有较多立构晶相关。

The PDLA-b-PEG-b-PDLA block copolymers with different PDLA molecular weights were used to modify poly (L-lactic acid)(PLLA). The effect of different chain structures of PDLA-b-PEG-b-PDLA on the properties of PLLA was investigated. The results indicate that the crystallization behavior of α crystal in the PLL A/PDLA 1k -PEG 2k -PDLA 1k blends is the same as in PLLA during the cooling process. However, the PDLA 5k -PEG 2k -PDLA 5k copolymers increases the crystallization temperature of α crystal from 96 ℃ to 130 ℃. Both of the crystallization time and spherulite size of α crystal of PLLA crystallized at 130 ℃ are reduced with addition of the block copolymers, while the decline level varied with the different chain structure. It shows a better promotion of the crystallization of α crystal for the specimen with PDLA 5k -PEG 2k -PDLA 5k copolymer. When stretched at room temperature, the blends display a changing from brittle to ductile fracture with the amount of PDLA1k -PEG 2k -PDLA 1k copolymer increased. However, the addition of PDLA 5k -PEG 2k -PDLA 5k has little effect on the tensile properties of PLLA in our experiments, showing brittle fracture of all the samples. It is thought to be related to the more stereocomplex crystallites in the PLLA/PD LA 5k -PEG 2k -PDLA 5k blends.