Bowls, vases and goblets—the microcrockery of polymer and nanocomposite morphology revealed by two-photon optical tomography

• Published in: Nature communications 2021-08, Vol.12 (1), p.5054-5054, Article 5054
• Main Authors: Yang, Shu-Gui, Wei, Zhen-Zhen, Cseh, Liliana, Kazemi, Pantea, Zeng, Xiang-bing, Xie, Hui-Jie, Saba, Hina, Ungar, Goran
• Format: Article
• Language: English
• Subjects: 639/301/1023/1025; 639/301/923/1028; 639/638/455/957; 639/925/930/328/1978; Additives; Biodegradability; Biodegradation; Confocal microscopy; Crystallization; Fluorescence; Humanities and Social Sciences; Imaging techniques; Labels; Material properties; Microscopy; Morphology; multidisciplinary; Nanocomposites; Nanoparticles; Nucleation; Plastics; Polyethylene; Polyethylenes; Polylactic acid; Polymer matrix composites; Polymers; Polypropylene; Pressure drop; Science; Science (multidisciplinary); Self-assembly; Spherulites; Tableware; Three dimensional composites
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-021-25297-w

On the >1 µm scale the morphology of semicrystalline plastics like polyethylene or Nylon features spherulites, “shish-kebabs”, cylinddrites and other crystalline aggregates which strongly affect mechanical and other material properties. Current imaging techniques give only a 2D picture of these objects. Here we show how they can be visualized in 3D using fluorescent labels and confocal microscopy. As a result, we see spherulites in 3D, both in neat polymers and their nanocomposites, and observe how unevenly nanoparticles and other additives are distributed in the material. Images of i-polypropylene and biodegradable poly(lactic acid) reveal previously unsuspected morphologies such as “vases” and “goblets”, nonspherical “spherulites” and, unexpectedly, “shish-kebabs” grown from quiescent melt. Also surprisingly, in nanocomposite sheets spherulite nucleation is seen to be copied from one surface to another, mediated by crystallization-induced pressure drop and local melt-flow. These first results reveal unfamiliar modes of self-assembly in familiar plastics and open fresh perspectives on polymer microstructure. The morphology of semicrystalline plastics on the 1-100 μm scale, such as spherulites, strongly affect mechanical and other properties of the material but currently only 2D imaging techniques are available. Here, the authors use fluorescence labels and confocal microscopy to visualize the internal structure of neat polymers and composites in 3D and reveal unsuspected morphologies.