聚合物流致成核的多尺度和多步排序,Chemical Reviews

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聚合物流致成核的多尺度和多步排序
Chemical Reviews ( IF 51.4 ) Pub Date : 2018-01-19 00:00:00 , DOI: 10.1021/acs.chemrev.7b00500
Kunpeng Cui ₁ , Zhe Ma ₂ , Nan Tian ₃ , Fengmei Su ₁ , Dong Liu ₄ , Liangbin Li ₁

Affiliation

流动诱导结晶（FIC）是典型的非平衡相变，并且是最大组的商业上有用的聚合物材料：半结晶聚合物的核心工业主题。对FIC的基本理解可以有益于物质系统中非平衡有序的研究，并有助于定制聚合物材料的最终特性。关于结晶过程，流动可以使动力学加速几个数量级，并诱导形成像烤肉串这样的定向微晶，这与流动对成核的主要影响有关，即成核密度和定向核的增加。FIC的主题已经研究了半个多世纪。最近，实验方法有了许多进展，例如同步辐射X射线散射，时间分辨率低至毫秒级的超快X射线探测器，以及新颖的实验室设备，可模拟接近真实加工条件的恶劣流场。通过这些先进方法的组合，可以更精确地（具有更高的时间分辨率和更大的长度范围）和定量地揭示FIC的演化过程。新发现挑战了经典的解释和理论，这些解释和理论主要来自静态或缓和流动条件，并引发了对FIC基础的重新考虑。这篇综述主要总结了实验结果，物理理解的进展以及对强流诱导的取向核的多尺度和多步性质的讨论。多尺度结构包括分段构象，构象有序堆积，全链尺度上的变形，以及微晶的宏观聚集。多步骤过程涉及构象转变，各向同性-向列转变，密度波动（或相分离），前体的形成和烤肉串微晶，这是成核过程中可能的有序过程。此外，还包括一些理论进展和建模工作。

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Multiscale and Multistep Ordering of Flow-Induced Nucleation of Polymers

Flow-induced crystallization (FIC) is a typical nonequilibrium phase transition and a core industry subject for the largest group of commercially useful polymeric materials: semicrystalline polymers. A fundamental understanding of FIC can benefit the research of nonequilibrium ordering in matter systems and help to tailor the ultimate properties of polymeric materials. Concerning the crystallization process, flow can accelerate the kinetics by orders of magnitude and induce the formation of oriented crystallites like shish-kebab, which are associated with the major influences of flow on nucleation, that is, raised nucleation density and oriented nuclei. The topic of FIC has been studied for more than half a century. Recently, there have been many developments in experimental approaches, such as synchrotron radiation X-ray scattering, ultrafast X-ray detectors with a time resolution down to the order of milliseconds, and novel laboratory devices to mimic the severe flow field close to real processing conditions. By a combination of these advanced methods, the evolution process of FIC can be revealed more precisely (with higher time resolution and on more length scales) and quantitatively. The new findings are challenging the classical interpretations and theories that were mostly derived from quiescent or mild-flow conditions, and they are triggering the reconsideration of FIC foundations. This review mainly summarizes experimental results, advances in physical understanding, and discussions on the multiscale and multistep nature of oriented nuclei induced by strong flow. The multiscale structures include segmental conformation, packing of conformational ordering, deformation on the whole-chain scale, and macroscopic aggregation of crystallites. The multistep process involves conformation transition, isotropic–nematic transition, density fluctuation (or phase separation), formation of precursors, and shish-kebab crystallites, which are possible ordering processes during nucleation. Furthermore, some theoretical progress and modeling efforts are also included.

更新日期：2018-01-19

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