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Article

Interaction of Poly L-Lactide and Tungsten Disulfide Nanotubes Studied by In Situ X-ray Scattering during Expansion of PLLA/WS2NT Nanocomposite Tubes

1
School of Mechanical and Aerospace Engineering, Queen’s University Belfast, Belfast BT9 5AH, UK
2
Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125, USA
3
Division of Sustainable Materials, ENEA, Centro Ricerche Portici, 80055 Portici, Italy
4
Division of Photovoltaics and Smart Networks, ENEA, Centro Ricerche Portici, 80055 Portici, Italy
5
Faculty of Sciences, Holon Institute of Technology, Holon 5810201, Israel
*
Author to whom correspondence should be addressed.
Academic Editor: Young-Sam Cho
Polymers 2021, 13(11), 1764; https://doi.org/10.3390/polym13111764
Received: 21 April 2021 / Revised: 19 May 2021 / Accepted: 24 May 2021 / Published: 27 May 2021
(This article belongs to the Special Issue Polymeric Materials as Scaffolds for Tissue Engineering)
In situ synchrotron X-ray scattering was used to reveal the transient microstructure of poly(L-lactide) (PLLA)/tungsten disulfide inorganic nanotubes (WS2NTs) nanocomposites. This microstructure is formed during the blow molding process (“tube expansion”) of an extruded polymer tube, an important step in the manufacturing of PLLA-based bioresorbable vascular scaffolds (BVS). A fundamental understanding of how such a microstructure develops during processing is relevant to two unmet needs in PLLA-based BVS: increasing strength to enable thinner devices and improving radiopacity to enable imaging during implantation. Here, we focus on how the flow generated during tube expansion affects the orientation of the WS2NTs and the formation of polymer crystals by comparing neat PLLA and nanocomposite tubes under different expansion conditions. Surprisingly, the WS2NTs remain oriented along the extrusion direction despite significant strain in the transverse direction while the PLLA crystals (c-axis) form along the circumferential direction of the tube. Although WS2NTs promote the nucleation of PLLA crystals in nanocomposite tubes, crystallization proceeds with largely the same orientation as in neat PLLA tubes. We suggest that the reason for the unusual independence of the orientations of the nanotubes and polymer crystals stems from the favorable interaction between PLLA and WS2NTs. This favorable interaction leads WS2NTs to disperse well in PLLA and strongly orient along the axis of the PLLA tube during extrusion. As a consequence, the nanotubes are aligned orthogonally to the circumferential stretching direction, which appears to decouple the orientations of PLLA crystals and WS2NTs. View Full-Text
Keywords: polylactide; tungsten disulfide nanotubes; nanocomposites; blow molding; WAXS; SAXS; bioresorbable vascular scaffold polylactide; tungsten disulfide nanotubes; nanocomposites; blow molding; WAXS; SAXS; bioresorbable vascular scaffold
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MDPI and ACS Style

Rocher, L.; Ylitalo, A.S.; Di Luccio, T.; Miscioscia, R.; De Filippo, G.; Pandolfi, G.; Villani, F.; Zak, A.; Menary, G.H.; Lennon, A.B.; Kornfield, J.A. Interaction of Poly L-Lactide and Tungsten Disulfide Nanotubes Studied by In Situ X-ray Scattering during Expansion of PLLA/WS2NT Nanocomposite Tubes. Polymers 2021, 13, 1764. https://doi.org/10.3390/polym13111764

AMA Style

Rocher L, Ylitalo AS, Di Luccio T, Miscioscia R, De Filippo G, Pandolfi G, Villani F, Zak A, Menary GH, Lennon AB, Kornfield JA. Interaction of Poly L-Lactide and Tungsten Disulfide Nanotubes Studied by In Situ X-ray Scattering during Expansion of PLLA/WS2NT Nanocomposite Tubes. Polymers. 2021; 13(11):1764. https://doi.org/10.3390/polym13111764

Chicago/Turabian Style

Rocher, Lison, Andrew S. Ylitalo, Tiziana Di Luccio, Riccardo Miscioscia, Giovanni De Filippo, Giuseppe Pandolfi, Fulvia Villani, Alla Zak, Gary H. Menary, Alex B. Lennon, and Julia A. Kornfield 2021. "Interaction of Poly L-Lactide and Tungsten Disulfide Nanotubes Studied by In Situ X-ray Scattering during Expansion of PLLA/WS2NT Nanocomposite Tubes" Polymers 13, no. 11: 1764. https://doi.org/10.3390/polym13111764

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