Abstract
The exceptional mechanical properties of polymer nanocomposites are achieved through intimate mixing of the polymer and inorganic phases, which leads to spatial confinement of the polymer phase1,2,3,4,5. In this study we probe the mechanical and fracture properties of polymers in the extreme limits of molecular confinement, where a stiff inorganic phase confines the polymer chains to dimensions far smaller than their bulk radius of gyration. We show that polymers confined at molecular length scales dissipate energy through a confinement-induced molecular bridging mechanism that is distinct from existing entanglement-based theories of polymer deformation and fracture. We demonstrate that the toughening is controlled by the molecular size and the degree of confinement, but is ultimately limited by the strength of individual molecules.
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Acknowledgements
This work was supported by the Air Force Office of Science Research Grant No. FA9550-12-1-0120 in the Low Density Materials Program. Characterization was performed in part at the Stanford Nano Shared Facilities (SNSF).
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S.G.I. and Y.M. made DCB specimens and collected and analysed fracture data. S.G.I. performed simulations. K.L. fabricated and characterized the hybrid nanocomposites. W.V. synthesized the nanoporous matrix. T.P.M. performed GPC analyses. S.G.I. and R.H.D. constructed the molecular bridging model. S.G.I., G.D. and R.H.D. wrote the paper and designed the study.
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Isaacson, S., Lionti, K., Volksen, W. et al. Fundamental limits of material toughening in molecularly confined polymers. Nature Mater 15, 294–298 (2016). https://doi.org/10.1038/nmat4475
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DOI: https://doi.org/10.1038/nmat4475
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