聚乳酸-酰胺11嵌段共聚物协同纤维素纳米晶反应挤出制备具有纳米连续相液滴的PLA复合材料及其对PLA增强增韧的机理

Poly(lactic acid) (PLA) has good properties and is an ideal alternative bio-based polymer for petroleum based polymers. However, its drawback is brittle and modification for toughening PLA always results reduced mechanical strength. In our previous work, esterification reaction between PLA and PA11 (polyamide 11) chains though reactive extrusion process was achieved for preparing PLA/PA11 blends, which showed unique phase morphology with nanoscale continuous phase dispersed into dispersed phase, and the elongation at break enhanced 13 times than pure PLA, while only resulted 14% less in modulus. This new strategy showed the effectiveness of manipulating mechanical properties through morphology control. To further improve this strategy for preparing PLA with both enhanced toughness and strength, this project plans to synthesize PLA-b-PA11 block copolymer with tunable structures by interfacial esterification reaction, fabricate PLA/PLA-b-PA11 blends through extrusion, and investigate the effects of shear force, structure of block copolymer on the morphology and properties of PLA/PLA-b-PA11 blends, and illustrate the mechanism of toughening PLA through manipulation of morphology and flexibility of PLA chans. Furthermore, this project plans to investigate factors such as shear force and reaction conditions on morphology evolution and mechanical properties of PLA/PLA-b-PA11/cellulose nanocrystal (CNC-g-) nanocomposites, and explore the evolution of phase droplet with nanoscales in size, and the mechanism of manipulating mechanical properties of composites through “shear force-block copolymer- CNC-g-”.

聚乳酸（PLA）综合性能优良，是替代石油基聚合物的理想材料。然其脆性大，增韧改性易致强度下降。项目前期以反应挤出进行界面酯交换制备PLA/PA11（尼龙11），发现PA11分散相包藏纳米级PLA连续相，共混物的断裂伸长率提高13倍，模量仅下降14%，初步获得以相形态调控其力学性能的新技术。为完善该技术用于制备高强高韧PLA，本项目以界面酯交换反应挤出合成结构可调的PLA-b-PA11，共混挤出制备PLA/PLA-b-PA11，考察剪切流场、共聚物结构等对共混物形态结构和性能的影响机制，阐述调控相形态和PLA分子链柔顺性增韧PLA的机理。考察剪切流场、反应条件等影响以反应挤出制备PLA/PLA-b-PA11/纤维素纳米晶（CNC-g）复合材料的相形态演变及力学性能的规律，探索复合材料纳米级相液滴尺寸特征的演变历程，获得“剪切流场、嵌段共聚物和CNC-g”调控PLA复合材料力学性能的新机理。

项目完成了反应挤出界面酯交换反应合成 聚乳酸-酰胺11嵌段共聚物（PLA-b-PA11）的机制研究，阐述了挤出温度、停留时间以及催化剂含量对PLA-b-PA11 嵌段共聚物分子量、热力学性能以及结晶的影响，探索 PLA-b-PA11 嵌段共聚物增韧聚乳酸（PLA）的机制。项目合成制备的PLA-b-PA11 嵌段共聚物能够有效促进PLA的柔韧性，其共混物具备高韧性及优异的综合力学性能。项目完成了PLA/PLA-b-PA11/CNC-g三元纳米复合材料形态与性能相互关系及增韧机理的研究。通过优化设计，三元复合材料的拉伸模量达到4.3GPa，断裂伸长率达到230%；与纯PLA相比，分别提高了1.2和47倍。阐明了复合材料组分对聚乳酸降解动力学的影响机制。研究成果将为生物基复合材料制备、改性及降解回收提供数据支撑和理论依据，促进新型生物基复合材料的发展。