Bonding-induced thermal transport enhancement across a hard/soft material interface using molecular monolayers

Abstract

Manipulating thermal transport across hard/soft material interfaces is important for composites which are critical for a wide range of applications, including electronic packaging, thermal storage, sensors and medicine. To increase the interfacial thermal conductance (G), a previous strategy has focused on using a self-assembled monolayer (SAM) to bridge the phonon spectra mismatch between the materials constituting the interface. Here, we introduce a general strategy aiming for interfaces which are incompatible with the previous strategy. Copper (Cu) and epoxy resin are chosen as representative materials constituting the interface. The proposed strategy relies on using a strongly bonding SAM to covalently connect Cu and epoxy. The thermal measurements show that G can be enhanced by as much as 11 fold. An interesting result is found that the Cu/epoxy interface, modified with the SAM used in the previous strategy, shows approximate 2-fold lower G. Through a series of experiments, including tensile strength and wettability tests, the formation and characters of bonds in different interface systems are explored and understood. The correlation between bonding characters and G is also elucidated. We demonstrate that when the structure of the soft material is complex, interfacial thermal transport should be tuned by covalent bonds rather than by phonon spectra match. Finally, the great potential of the proposed strategy in manipulating the thermal properties of nanocomposites is illustrated here with a theoretical prediction.

Molecular Structure Effect of a Self-Assembled Monolayer on Thermal Resistance across an Interface

“…These studies have investigated the effects of various characteristics of SAMs on the interfacial thermal conductance from two different points of view: (1) considering accurate information about SAM, including SAM coverage [4,9,10], length of SAMs [4,[11][12][13], distinct functional group [9,[13][14][15][16][17], heterogeneous fin structure [18], vibrational spectral overlapping [9], nanoscale roughness [19][20][21], and so on. Huang et al [16] investigated interfacial thermal conductance (ITC) across the interface of water and gold tailored with -CH 3 SAM, -OHSAM, and -COOHSAM.…”

Modulating Thermal Transport in Polymers and Interfaces: Theories, Simulations, and Experiments

“…Cooper/epoxy 12.5 Thermal measur ements [183] Cooper/ SAM-CH 3 / epoxy 7.1 Thermal measur ements [183] Cooper/ SAM-NH 2 / epoxy 142.9 Thermal measur ements [183] CNT…”

A Theoretical Review on Interfacial Thermal Transport at the Nanoscale

“…However, this mechanism is mainly suitable for SAMs and contacting materials with similar chemical compositions, which produces a better phonon vibration mechanism. In addition, for some soft materials with complex structures, forming strong chemical bonds is a better method to tune the ITC, as it is difficult to obtain similar structured SAMs . In addition, stronger interfacial bonding is often more important than the PDOS overlap in enhancing the ITC .…”

“…In addition, for some soft materials with complex structures, forming strong chemical bonds is a better method to tune the ITC, as it is difficult to obtain similar structured SAMs. [169] In addition, stronger interfacial bonding is often more important than the PDOS overlap in enhancing the ITC. [165] The role of the CH 3 [HS(CH 2 ) 5 CH 3 ] SAM at the interface between Au and organic liquids is not obvious, even though the CH 3 SAM has the same carbon backbone as the organic liquids (shown in Figure 12a).…”