基于立构复合晶体对核壳橡胶粒子分布的有效调控实现聚乳酸材料的高性能化

Core-shell rubbers (CSR) composed of rubbery core and glassy shell has become an attractive choice to improve the toughness of polylactides (PLA) due to their controllable structure and shape, as well as desired interfacial compatibility with PLA. However, a low toughening efficiency of CSR for PLA is usually obtained, which inevitably causes a signifcant deterioration in mechanical strength, modulus, and heat resistance of PLA. In this project, stereocomplex (SC) crystallites are constructed in the blend matrix through melt-mixing poly(L-lactide) (PLLA)/CSR blends with poly(D-lactide) (PDLA). Both of the enhancement effect of SC crystallites on the viscosity of PLLA and the strong volume exclusion effect of SC crystallites on the CSR particles can induce the organization of the CSR particles into a network-like structure that possesses a high toughening efficiency within the matrix, finally endowing PLLA/CSR blends with good stiffness-toughness balance and super heat resistance. The microstructure of SC crystallites formed in the blend matrix will be tailored by controlling the PDLA properties. The synergistic effect of blend viscosity ratio and volume exclusion intensity, dominated by adjusting the microstructure of SC crystallites, on the fomation of CSR network-like structrure will be illustrated, and a mechnism model for the fomation of CSR network-like structrure induced by SC crystallites will be established. Through the qualitative and quantitative analysis of the mophology of CSR network-like structrure as well as the effect of the mophology parametters on the blend performance, the relationship of SC crystallites, CSR network-like structrure, and blend performance will be set up. The completion of this project will provide a promising and industrially meaningful route to develop high performanced PLLA-based materials with the aid of SC crystallites.

由橡胶核和塑料壳构成的核壳橡胶因具有结构形态可控、与聚乳酸（PLA）相容性好等优点而成为改善PLA韧性的重要增韧改性剂。但核壳橡胶增韧效率低，易导致PLA强度、模量、耐热等性能的下降。本项目通过将左旋聚乳酸（PLLA）/核壳橡胶共混物与右旋聚乳酸（PDLA）进行熔融共混，利用基体中原位形成的立构复合（SC）晶体对基体粘度的调节作用以及对核壳橡胶的体积排斥作用，促使核壳橡胶形成具有高增韧效率的类网络结构，从而实现共混物的刚韧平衡与高耐热。研究从调控SC晶体的物理结构入手，通过系统分析SC晶体调控的体系粘度比、体积排斥作用强度对类网络结构形成的影响，阐明二者的协同作用机制，建立SC晶体诱导核壳橡胶形成类网络结构的机理模型；定量表征核壳橡胶类网络结构的形态并分析其对共混物性能的影响，建立SC晶体-类网络结构形态-性能之间的关系，为基于SC晶体调控核壳橡胶粒子分布制备高性能PLLA材料提供新思路。

由橡胶核和塑料壳构成的核壳橡胶（CSR）因具有结构形态可控、与聚乳酸（PLA）相容性好等优点而成为改善PLA韧性的重要增韧改性剂。但CSR粒子增韧效率低，易导致PLA强度、模量、耐热等性能的下降。本项目通过将左旋聚乳酸（PLLA）/CSR共混物与右旋聚乳酸（PDLA）进行熔融共混，利用PLLA基体中原位形成的立构复合（SC）晶体促使CSR粒子形成具有高增韧效率的类网络结构，从而同步实现了PLLA/PDLA/CSR共混物的刚韧平衡与高耐热。主要研究内容包括：（1）合成了一系列不同结构的PDLA，探索了PDLA的含量、分子量、光学纯度、分子链拓扑结构等参数对PLLA/PDLA/CSR共混物中SC晶体微观结构的影响；（2）系统研究了SC晶体微观结构对共混物体系熔体粘度比、对CSR粒子产生的体积排斥作用强度的影响，并详细分析了二者对CSR类网络结构的形成及形态变化的影响规律，阐明了SC晶体诱导CSR粒子形成类网络结构的机理，初步实现了CSR类网络结构的可控制备；（3）揭示了CSR类网络结构形态对共混物冲击韧性、强度与模量、耐热性的影响规律，分析了CSR类网络结构的增韧机理，有效建立了SC晶体结构-CSR类网络结构形态-共混物性能三者之间的关系；（4）在此基础上，探索了新型酰胺类成核剂对SC晶体微观结构的调控作用，还探讨了SC晶体以及功能性纳米粒子调控CSR粒子分布技术在制备具有优异透明性、力学以及功能性PLA材料中的应用。这些研究工作可为通过调控CSR粒子的分布行为制备高性能PLA共混/复合材料提供新思路以及理论指导，有利于大大拓展PLA材料的应用范围，因而具有重要的理论研究价值和应用价值。