链段序列结构对丙交酯/己内酯共聚物性能的影响研究

Effects of Chain Segment Sequence Structures on the Properties of L-Lactide/ε-Caprolactone Copolymers

聚乳酸(PLA)是常见的生物基可降解塑料之一。通过共聚改性,引入柔性链段[如聚己内酯(PCL)],可以改善PLA质脆和韧性差的问题,但PLA共聚物链段序列结构与其结晶和机械性能的关系不明确。本工作制备了聚(丙交酯-co-己内酯)(PLCL)无规共聚物和PLA-PCL-PLA(L-C-L)三嵌段共聚物,研究分子链序列结构对共聚物结晶性能的影响。结果表明,随着己内酯(CL)比例的提高,PLCL中PLA链段的平均序列长度变短,其结晶速率和结晶度迅速降低,使其杨氏模量降低、断裂应变增大。与之不同的是,L-C-L的序列结构不变,其结晶速率和结晶度无明显变化,但杨氏模量降低、断裂应变增大,韧性提高。

Polylactic acid(PLA)is one of the common biodegradable plastics.Copolymerization modification to introduce flexible chain segments(such as polycaprolactone,PCL)can improve the brittleness and poor flexibility of PLA,but the relationship between the chain segment sequence structures of PLA copolymers and their crystallization or mechanical properties is unclear.The poly(lactide-co-caprolactone)(PLCL)random copolymers and PLA-PCL-PLA(L-C-L)triblock copolymers were synthesized,and the effect of the chain segment sequence structures on the crystallization of the copolymers was investigated.The results showed that with the increase of caprolactone proportion,the average sequence length of PLA segment in PLCL shortens,and the crystallization rate and crystallinity of PLCL decreased dramatically,resulting in the decrease of Young’s modulus and the increase of fracture strain.Conversely,the chain segment sequence structures of do not change,nor do its crystallization rate and crystallinity.However,the Young’s modulus of L-C-L decreases and the fracture strain increases,showing the improvement of flexibility.