生物质聚羟基脂肪酸酯多尺度有序结构的构筑及相关机理研究

Oxalamide-derived nucleating agent (OXA-NA) with lattice match and tunable structure/properties are designed and synthesized. The OXA-NA is used for tailoring the crystallization behavior of poly(hydroxyalkanoate)s (PHAs). The mechanism of PHAs rapid crystallization and lamellar orientation that induced by OXA-NA fibrils will be investigated. Meanwhile the effect of structure, concentration and shear conditions on the formation, destruction and orientation of the OXA-NA fibrils (or network) will be studied. The orientation process and degree of the OXA-NA fibrils are controlled. A multi-scale ordered structure of the PHAs is then designed by the orientation of both OXA-NA fibrils and PHAs lamellae. The mechanism and preparation method of the ordered structure is going to be revealed based on aforementioned study and crystallization kinetics. The structure-property relationship, taking PHAs film as an example, will be investigated. Consequently biomass films with fast processing speed and superior properties would be obtained. This work will not only enriches the theory of polymer crystallization in the presence of nucleating agents and shear, but also establishes a new method for rapid and ordered crystallization of polyester via a synergetic effect of OXA-NA fibrils orientation and shear field. The study would provide a theoretical guidance to processing and application of polyesters, thus it is of importance in both fields of research and application.

从分子水平设计合成一系列与聚羟基脂肪酸酯（PHAs）晶格匹配、结构与物性可控的乙二酰胺基成核剂（OXA-NA），用于调控PHAs的结晶行为。揭示OXA-NA相分离成纤诱导PHAs快速结晶和片晶在OXA-NA表面取向生长的机理；研究OXA-NA的分子结构、浓度以及外场作用对OXA-NA微纤（或网络）形成、破坏及取向的影响规律，控制其取向过程和取向度；通过OXA-NA微纤取向和PHAs片晶定向生长的协同效应构筑PHAs多尺度有序结构，结合实验数据和动力学模型阐明新体系中PHAs有序结构形成的机理与方法；以薄膜为考察对象，通过结构与性能的关联，制备成型快、性能卓越的生物质薄膜材料。本研究不仅可丰富成核剂与剪切共同诱导聚合物结晶的理论，还将建立一种通过成核剂成纤取向与剪切外场协同诱导生物质聚酯快速、有序结晶的新方法，为PHAs及其它聚酯的加工应用提供有力的理论支撑，具有重要的科学与现实意义。

聚羟基脂肪酸酯（PHAs）具有优异的生物降解性和生物相容性，但韧性差、结晶慢等问题局限了其规模化应用。针对成核密度低、结晶速率慢这一技术瓶颈，本研究首先设计合成了系列不同化学结构的自组装型小分子成核剂（OXA），系统研究了OXA的化学结构、浓度和外场条件对PHAs结晶动力学和成核效率的影响规律，揭示了OXA原位成纤诱导PHAs快速结晶和晶体在微纤表面取向生长的机理，使PHAs的半结晶时间缩短了95%。进而利用Maxwell离散松弛图谱等方法确定了PHAs熔体中分子链发生取向和拉伸的临界条件，并通过OXA微纤和PHAs取向构筑了多尺度有序结构，建立了OXA与剪切协同促进PHAs有序结晶的机制，显著提高了PHAs的高温结晶速率。上述研究思想还被用于生物质纳米粒子诱导PHAs结晶的相关研究、以及聚乳酸等生物聚酯的结晶与性能调控，在改善生物聚酯结晶行为的同时赋予材料优异的力学性能。最后，以PHAs薄膜为例，研究了OXA诱导PHAs超薄膜熔体结晶动力学与单晶形貌的控制方法，并且利用功能纳米粒子诱导结晶构筑了系列抗菌性、高阻隔、耐高温的PHAs薄膜材料。该研究不仅丰富了成核剂与剪切协同诱导聚合物结晶的理论，还为生物聚酯的加工与应用提供了有力的理论支撑。