通过立构复合晶与长链支化共聚物链缠结的协同作用实现聚乳酸的超增韧

Toughening modification is one of the most important issue in research and application of brittle polymer such as polylactide (PLA). However, in most cases, typical modification method using cross-linked elastomer may come at the expense of biodegradability and thermoplastic processability, although this method exhibited very good toughening effect for PLA. In this research, flexible aliphatic polyester with controllable long-chain branched structure will be designed and copolymerized with PDLA, which is the stereoisomer of PLLA, and then used for toughening PLLA. Taking advantage of stereocomplex crystallites with very high stability formed between PDLA segments and PLLA matrix, the phase structure and chain entanglements owing to the long chain branched structure could be effectively controlled and stabilized, resulting in an elastic physical network with enhanced ability to dissipate the impact energy. After systematically evaluating the influence of chemical composition, molecular topology, blend composition, and crystallization conditions on the morphology, phase structure and properties, the inherent relation between structure and properties will be obtained and the toughening mechanism will be proposed. This research will not only address the key issue involved in preparation of PLA with full biodegradability and optimized overall performance, but also provide novel strategy and guidance for toughening and modifying brittle polymers.

增韧改性是聚乳酸（PLA）等脆性高分子研究与应用中最核心的关键问题之一，常规交联弹性体共混增韧改性往往以牺牲聚合物的可生物降解性和热塑加工性为代价，限制了其在生物医用和环境友好材料领域更广泛应用。本研究设计合成具有可控结构的长链支化柔性脂肪族聚酯，同时引入常规PLLA基体的旋光异构体PDLA为共聚链段，并用于PLLA的共混增韧。利用PDLA与PLLA基体形成稳定的立构复合晶，调控两相结构并稳定长链支化脂肪族聚酯的链缠结作用，在二者协同作用下形成网络，从而有效提高增韧相对外力的耗散，实现超增韧。系统研究共聚物的化学组成、分子拓扑结构、共混物配比、结晶条件等因素对增韧改性PLLA微观形貌、两相结构以及各种理化性能的影响，建立结构与性能之间的内在联系，探讨并总结增韧机理。研究不仅可以获得具有优化综合性能、可完全生物降解的改性PLLA，还可以为脆性高分子的增韧研究及高性能化提供新的方法与借鉴。

增韧改性是聚乳酸（PLA）等脆性高分子研究与应用中最核心的关键问题之一，常规交联弹性体共混增韧改性往往以牺牲聚合物的力学强度、可生物降解性、热塑加工性等为代价，限制了其在生物医用和环境友好材料领域更广泛应用。本研究通过设计合成一系列具有可控分子结构的嵌段共聚物，在其分子中引入离子基团等结构，构建基于分子间相互作用并贯穿增韧相和基体相的一体化物理交联网络，并用于PLA的增韧改性，获得了具有优化综合性能、可完全生物降解的改性PLA；系统研究了共聚物的化学组成、分子拓扑结构、共混物配比、结晶条件等因素对增韧改性PLLA微观形貌、两相结构以及各种理化性能的影响，建立结构与性能之间的内在联系，探讨并总结增韧机理。设计合成了含苯基次磷酸离子基团的共聚物，并与多聚磷酸铵（APP）协同阻燃/增韧改性PLA。在以上研究基础上，将该一体化网络增韧机理进一步拓展应用于环氧树脂、甲壳素纳米晶复合材料其他聚合物体系的高效增强增韧以及功能化应用，为脆性高分子的增韧研究及高性能化、功能化提供了新的思路与借鉴。

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