多分散烯烃嵌段共聚物OBC介观尺度相形态调控及加工定制研究

As commercial olefinic thermoplastic elstomer (TPE), ethylene-(1-octene) multiblock copolymer (OBC) generally undergoes mesophase separation and self-assembly into periodic nanostructures due to its unique block polydispersity (PDI≈2), meaning possibility of functional applications. However, most of the commercial OBCs present as weakly segregated system because of high similarity between different blocks, and make it difficult to achieve such interesting ordered structures under normal processing conditions. In this proposal, we confront this challenge and are trying to solve it via the aid of adding the mineral oil (MO) into OBC system. Based on the thermodynamic and kinetic considerations, the selective interaction of MO with the soft-segments can enhance segregation strength of OBC through regulating the Flory-Huggins parameter (χ) and suppressing lamellae assembly during crystal development. Furthermore, the parent homopolymer (polyethylene, PE) was introduced to enrich the phase morphologies and establish phase diagram for the ternary system. The co-crystallization structure can also slow down molecular relaxation of the hard-segments and increase the structure ordering. Great efforts will be made on distinguishing key factors and important processing parameters for these ordered phase morphologies at mesoscale in aiming of the reappearance of phase structure at equilibrium state and freezing new metastable state structures. After the evaluation of mechanical properties of the samples, close relationship between structure and property will be established. Finally, our project will not only enrich the knowledge of structure regulation of polydisperse block copolymers, but also lay great foundation for the high value-added or functional industrial applications of OBCs with special phase structures.

乙烯-（1-辛烯）多嵌段共聚物(OBC)因其嵌段的多分散性，具备形成介观尺度上周期性有序结构的潜力，这为其功能化应用提供了可能。针对OBC软硬段相似性高而导致的体系弱相分离问题，本项目拟采用添加矿物油（MO）、均聚物聚乙烯（PE）来调控OBC相形态，并通过加工手段实现介观有序结构的构筑。MO的加入能够提高软段分子链活动性，从而调节软硬段Flory-Huggins参数和抑制片晶组装，实现OBC微相分离的强化；进一步通过添加PE实现三元体系平衡态相图构建，同时利用共结晶结构延缓多重相变过程中硬段分子链松弛、提高结构有序性；最后，在明确相形态加工重现的核心影响因素和关键工艺参数的基础上，借助加工设备定制OBC介观有序结构，并阐述加工制品中相结构对其物理性能的影响规律。本项目的顺利开展不仅能够丰富多分散嵌段共聚物相形态调控的理论，而且能够为商业化烯烃嵌段共聚物中功能结构的工程化实现奠定基础。

乙烯-（1-辛烯）多嵌段共聚物(OBC)具备形成介观尺度上周期性有序结构的潜力，实现其微观相形态的定构加工是高值化和功能化应用的重要基础。在本基金的资助下，针对OBC弱相分离的问题深入开展了介观相分离行为和结晶行为的调控研究，取得了以下主要研究成果：1.具有高分子量和软硬段辛烯含量差异大的OBC品种其相分离强度较高，且结晶和介观相分离存在竞争效应。2.选择性矿物油（MO）的填充提高OBC软段分子链运动活性，长时退火实现结晶解耦合从而促进介观相分离。3. MO小分子选择性分布在OBC/MO物理凝胶的软相区从而降低晶体成核密度和提升凝胶透明性，且力学性能高效可调节。4.低分子量聚乙烯蜡流动性高且与OBC相容性好，少量添加起到显著成核和加速结晶效果，添加量提升后促进形成突破型结晶。5.少量线性聚乙烯与OBC溶液共混的体系形成共结晶结构，同时结晶形态对PE分子链长有显著的依赖性；耦合剪切外场后共混物形成取向晶体，长链聚乙烯则诱导形成串晶结构，导致共混物力学性能出现弹性体-塑料突变行为。本项目通过对OBC及其共混体系结晶/介观相分离耦合相形态的充分认识，进一步明确了对加工薄膜或制品中微观结构对力学性能的影响规律，这不仅丰富了多分散嵌段共聚物的相形态调控理论，而且能为其功能化应用奠定基础。此外，我们在本课题执行过程中还发展了其他OBC结构调控的思路，其中包括：1.成核剂的异相成核效应加速OBC硬段结晶，成核密度增加降低球晶尺寸，样品透明性显著提升。2.DCP轻度交联OBC构筑双网络弹性体保证良好热塑性的同时显著提升力学性能。这些进展也都能为多嵌段共聚物弹性体的设计和调控提供参考。