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Mayank Garg1 2 Jia En Aw3 2 Mostafa Yourdkhani2 Evan Lloyd4 2 Adam Ladd1 Scott White3 2 Nancy Sottos1 2

1, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States
2, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States
3, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States
4, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States

Complex vascular architectures have been manufactured through removal of sacrificial templates embedded in polymer substrates using the Vaporization of Sacrificial Component (VaSC) technique[1]. Prior work with VaSC required high temperatures (ca. 200 °C) and long exposure times under vacuum, limiting application of the process to polymer matrices that remain stable under these conditions. In this work, the feasibility of using cyclic-poly(phthalaldehyde) (cPPA) as a sacrificial polymer for rapid vascularization of polymers and polymer composites at lower temperatures is investigated. cPPA is a metastable polymer which depolymerizes completely into monomer units upon exposure to acidic or elevated temperature conditions[2]. As a first demonstration, rectangular solvent cast cPPA films (15 mm x 5 mm x 300 μm) were embedded in a poly(dicyclopentadiene(DCPD)) matrix and depolymerized at temperatures ranging from 95 – 110 °C within 3-1 hours, respectively. Successful vascularization was confirmed by optical imaging and pumping fluid through the resulting channel. Next, we investigated the simultaneous degradation of cPPA templates during an exothermic curing reaction of the matrix. DCPD monomer was partially cured as a gel with embedded cPPA fibers. A rapid exothermic Frontal Ring Opening Metathesis Polymerization (FROMP) of the gel was initiated with a thermal stimulus[3]. The temperature of the front (ca. 150 °C) spontaneously depolymerized the cPPA fibers to create microchannels in fully cured poly(DCPD) matrix in less than 3 minutes. Current research is focused on creating more robust melt-processed cPPA fibers and 3D printed scaffolds to expand the range of vascular architectures for adaptive and environmentally responsive structural materials with properties like self-healing, self-cooling and electromagnetic reconfigurability.


References
[1] R. C. R. Gergely, S. J. Pety, B. P. Krull, J. F. Patrick, T. Q. Doan, A. M. Coppola, P. R. Thakre, N. R. Sottos, J. S. Moore, and S. R. White, Adv. Func. Mater. 25, 1043 (2014).
[2] H. L. Hernandez, S.-K. Kang, O. P. Lee, S.-W. Hwang, J. A. Kaitz, B. Inci, C. W. Park, S. Chung, N. R. Sottos, J. S. Moore, J. A. Rogers, and S. R. White, Adv. Mater. 26, 7637 (2014).
[3] I. D. Robertson, L. M. Dean, G. E. Rudebusch, N. R. Sottos, S. R. White and J. S. Moore, ACS Macro Letters 6, 609 (2017)

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