无定形结晶聚合物共混物的 4D-STEM 分析：结合纳米晶体和 RDF 映射。,Microscopy and Microanalysis

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无定形结晶聚合物共混物的 4D-STEM 分析：结合纳米晶体和 RDF 映射。
Microscopy and Microanalysis ( IF 2.9 ) Pub Date : 2021-07-30 , DOI: 10.1017/s1431927621006577
Jennifer Donohue ₁ , Karen C Bustillo ₂ , Steven E Zeltmann ₁ , Colin Ophus ₃ , Benjamin Savitzky ₃ , Mary Ann Jones ₄ , Gregory F Meyers ₄ , Andrew Minor ₅

Affiliation

多相聚合物体系和共混物的纳米级形态，特别是在界面处和附近，对于了解界面粘附机制及其对整体机械性能的影响至关重要。为了在具有代表性的采样上可视化这种形态，需要一种快速的高分辨率技术来映射具有大视场的结晶域和无定形域。透射电子显微镜 (TEM) 提供所需的高分辨率。然而，TEM 在聚合物中的应用受到电子束敏感性、低 Z 元素的低散射强度以及难以区分通常具有紧密化学和结构组成的聚合物的严重限制。传统上为了规避这一点，使用重金属污渍来引入人工对比，但这种对比可能很难解释，因为它提供的结构信息很少，而且通常会导致伪影。四维扫描 TEM (4D-STEM) 是一种新兴技术，在相对较大的样品区域上具有高空间分辨率，可提供丰富的结构信息。然而，光束损伤限制了其在软材料和聚合物共混物中的应用。在这里，我们探索使用高速检测器、小聚光器孔径和高通量处理软件对聚合物共混物的无定形和结晶区域进行 4D-STEM 表征。具体来说，我们展示了一种低剂量 4D-STEM 技术，用于可视化极其光束敏感的半结晶等规聚丙烯和乙烯-辛烯共聚物 (iPP/EOC) 多层薄膜中的纳米结构。

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4D-STEM analysis of an amorphous-crystalline polymer blend: combined nanocrystalline and RDF mapping.

Nanoscale morphology of multiphase polymer systems and blends, particularly at and near interfaces, is critical to understanding interphase adhesion mechanisms and their impact on bulk mechanical properties. To visualize this morphology over a representative sampling, a fast high-resolution technique for mapping both crystalline and amorphous domains with a large field of view is needed. Transmission electron microscopy (TEM) offers the high resolution needed. However, the application of TEM to polymers is severely limited by the electron beam sensitivity, low scattering intensity from low-Z elements, and difficulty in differentiating polymers which often have close chemical and structural makeup. To circumvent this traditionally, a heavy metal stain is used to introduce artificial contrast, but this contrast can be very difficult to interpret as it provides little structural information and often results in artifacts. Four-dimensional scanning TEM (4D-STEM) is an emerging technique with high spatial resolution over a relatively large sample area which provides a wealth of structural information. However, beam damage has limited its applications for soft materials and polymeric blends. Here we explore the use of high-speed detectors, small condenser apertures, and high throughput processing software for 4D-STEM characterization of both the amorphous and crystalline regions of polymer blends. Specifically, we demonstrate a low-dose 4D-STEM technique for visualizing nanostructure in extremely beam sensitive semicrystalline isotactic polypropylene and ethylene-octene copolymer (iPP/EOC) multilayer films.

更新日期：2021-07-30

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