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.

Molecularly-induced roughness and oxidation in cobalt/organodithiol/cobalt nanolayers synthesized by sputter-deposition and molecular sublimation

“…For instance, recent theoretical calculations on multilayered stacks of Au/MNL/Au interfaces have indicated the possibility of emergent phenomena, such as viscoelastic bandgaps. 13 Metal-oxide multilayers 14,15 with interfacial MNLs can simultaneously exhibit optical transparency, high electrical and low thermal conductance, with mechanical flexibility. 7,16 Hybrid multilayer composites with alternating organic and inorganic nanolayers are typically synthesized by combining atomic and molecular layer deposition.…”

Nanomolecularly-induced Effects at Titania/Organo-Diphosphonate Interfaces for Stable Hybrid Multilayers with Emergent Properties

“… 1 Our prior works indeed support the emergence of unexpected properties, such as loading-frequency-dependent interfacial toughening to levels beyond the static-load toughness 6 and viscoelastic band gaps. 6 , 7 Nanoscale multilayering of inorganic/MNL interfaces also allows the possibility of inducing properties such as those seen in nacre and bone, 8 but via smaller length scale phenomena that are not constrained by biological processes. Such properties are attractive for diverse applications including microelectro-mechanical-systems, 9 self-healing/destructing materials, 10 , 11 and transparent conductors.…”

Strain hardening and toughening in metal/molecular nanolayer/metal nanosandwiches

“…More recently, molecular dynamics simulations have predicted MNL-induced emergent properties, such as viscoelastic bandgaps in multilayered metal/MNL structures. 27 Revealing the atomistic mechanisms of MNL-triggered interface strengthening and toughening would be invaluable for designing hybrid organic-inorganic interfaces with enhanced stability and dynamic responses. 12,27,28 Possible applications include thermal expansion mismatch mitigation, hybrid multilayers with emergent properties, (e.g., high toughness, optically transparent electrical conductors), and thermoelectrics.…”

“…27 Revealing the atomistic mechanisms of MNL-triggered interface strengthening and toughening would be invaluable for designing hybrid organic-inorganic interfaces with enhanced stability and dynamic responses. 12,27,28 Possible applications include thermal expansion mismatch mitigation, hybrid multilayers with emergent properties, (e.g., high toughness, optically transparent electrical conductors), and thermoelectrics. 12 Here, we present the results of ab initio molecular dynamics (AIMD) simulations of tensile deformation of Au/MNL/Au nanosandwich supercells to capture MNL-induced interfacial strengthening and toughening.…”