Molecular Bridge Enables Anomalous Enhancement in Thermal Transport across Hard‐Soft Material Interfaces

Abstract

Conventional wisdom tells us that interfacial thermal transport is more efficient when the interface adhesion energy is enhanced. In this study, it is demonstrated that molecular bridges consisting of small molecules chemically absorbed on solid surfaces can enhance the thermal transport across hard-soft material interfaces by as much as 7-fold despite a significant decrease in the interface adhesion energy. This work provides an unconventional strategy to improve thermal transport across material interfaces.

Aromatic molecular junctions between graphene sheets: a molecular dynamics screening for enhanced thermal conductance

“…In particular, the inefficiency of phonon transfer within a network of conductive particles in contact has been related to the "soft" interface, which does not allow transfer of efficient vibrational modes of phonons 7,20 . A possible approach to decrease this contact resistance is by grafting molecular junctions 21 between nanoparticles, to increase the contact stiffness and enhance phonon transfer [22][23] .…”

A Theoretical Review on Interfacial Thermal Transport at the Nanoscale

“…Another practical approach to functionalizing contacting heterointerfaces is the introduction of SAMs, which can change the vibrational mismatch and bond strength between interfaces by varying the SAM end‐group functionality. Both experimental and simulation results clearly show that SAMs can enhance the TC of contacting interfaces, even though two new interfaces and an additional layer are created . Take the SAMs applied between a quartz (QZ) and Au film as an example; the transfer printing technique was applied to fabricate QZ–SAM–Au junctions ( Figure a), and the molecular schematics with alterable tunable SAM end‐groups are shown in Figure b .…”

“…SAMs are more widely used to tune the ITC of interfaces with highly mismatched vibrational properties . The experimental results of Sun et al show that introducing a SAM between the gold–PE interface can increase the ITC by 7‐fold, and the temperature profiles obtained by MD simulations for the Au–PE and Au–SAM–PE interfaces ( Figure ) are very different—the calculated temperature drop (Δ T ) at the Au–PE interface is much larger than that at the Au–SAM–PE interface. ITC can be calculated through Equation , and introducing a SAM can clearly achieve stronger interfacial heat transfer.…”

“…b,c) Steady‐state temperature profiles of bare gold/PE and gold/SAM/PE interfaces. Reproduced with permission . Copyright 2014, Wiley‐VCH.…”

“…The SAM end‐groups play a dominant role in enhancing the ITC; furthermore, the additional factor of the SAM chain length has also been investigated in many papers. Sun et al observed that the overall ITC increased with the SAM chain length when the number of carbon atoms was no more than 12. Meier et al also observed an increase in the ITC with a reduction in the SAM chain length.…”