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Introducing molecular nanolayers (MNLs) is attractive for enhancing the stability of, and inducing unusual properties at, inorganic thin film interfaces. Although organic molecules anchored to inorganic surfaces have been studied extensively, property enhancement mechanisms underpinned by molecular assemblies at inorganic thin film interfaces are yet to be revealed and understood. Here, ab initio molecular dynamics simulations of tensile strain of Au/MNL/Au thin film nanosandwich models provide insights into molecularly induced strain hardening and toughening. Au/MNL/Au nanosandwiches support up to ≈30% higher stresses and exhibit up to ≈140% higher toughness than pure Au slab models. Both hardening and toughening are governed by molecular length and terminal chemistry in the MNL. Strong Au/MNL interface bonding and greater molecular length promote defect creation in Au, which results in strain hardening. Accommodation of increasing post-hardening strains in the MNL mitigates the stress increase in the Au slabs, delays interface fracture, and contributes to toughening. Remarkably, toughening correlates with equilibrium interface strain, which could be used as a proxy for efficiently identifying promising inorganic/MNL combinations that provide toughening. Our findings are important for the discovery and design of inorganic–organic interfaces, nanomaterials, and composites.
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Viscoelastic bandgap in multilayers of inorganic–organic nanolayer interfaces
Abstract Incorporating molecular nanolayers (MNLs) at inorganic interfaces offers promise for reaping unusual enhancements in fracture energy, thermal and electrical transport. Here, we reveal that multilayering MNL-bonded inorganic interfaces can result in viscoelastic damping bandgaps. Molecular dynamics simulations of Au/octanedithiol MNL/Au multilayers reveal high-damping-loss frequency bands at 33 ≤ ν ≤ 77 GHz and 278 ≤ ν ≤ 833 GHz separated by a low-loss bandgap 77 ≤ ν ≤ 278 GHz region. The viscoelastic bandgap scales with the Au/MNL interface bonding strength and density, and MNL coverage. These results and the analyses of interfacial vibrations indicate that the viscoelastic bandgap is an interface effect that cannot be explained by weighted averages of bulk responses. These findings prognosticate a variety of possibilities for accessing and tuning novel dynamic mechanical responses in materials systems and devices with significant inorganic–organic interface fractions for many applications, e.g., smart composites and sensors with self-healing/-destructing mechanical responses.
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- Award ID(s):
- 2135725
- PAR ID:
- 10368405
- Publisher / Repository:
- Nature Publishing Group
- Date Published:
- Journal Name:
- Scientific Reports
- Volume:
- 12
- Issue:
- 1
- ISSN:
- 2045-2322
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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