A molecular dynamics study on heat conduction characteristics inside the alkanethiolate SAM and alkane liquid

Kikugawa, Gota; Ohara, Taku; Kawaguchi, Tohru; Kinefuchi, Ikuya; Matsumoto, Yoichiro

doi:10.1016/j.ijheatmasstransfer.2014.07.040

Cited by 38 publications

(18 citation statements)

References 46 publications

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“…Therefore, we can estimate that thermal conductivity in the direction of intermolecular chains is ∼100 W/(m·K) if the packing density is 10 19 m –2 and the ballistic phonon mean free path is ∼100 nm, which is consistent with Shen’s result. In fact, self-assembled monolayers (SAMs), in which alkane chains align along the heat flow, exhibit a significantly high thermal conductivity compared to the bulk liquid of the same alkane molecules . These results indicate that depending on the aggregation structure of chains, even polymers without fillers can be sufficiently performant as a TIM.…”

Section: Introductionmentioning

confidence: 99%

Cross-Plane and In-Plane Heat Conductions in Layer-by-Layer Membrane: Molecular Dynamics Study

et al. 2020

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A material with anisotropic heat conduction characteristics, which is determined by molecular scale structure, provides a way of controlling heat flow in nanoscale spaces. As such, here, we consider layer-by-layer (LbL) membranes, which are an electrostatic assembly of polyelectrolyte multilayers and are expected to have different heat conduction characteristics between cross-plane and in-plane directions. We constructed models of a poly(acrylic acid)/polyethylenimine (PAA/PEI) LbL membrane sandwiched by charged solid walls and investigated their anisotropic heat conduction using molecular dynamics simulations. In the cross-plane direction, the thermal boundary resistance between the solid wall and the LbL membrane and that between the constituent PAA and PEI layers decrease with increasing degree of ionization (solid surface charge density and the number of electric charges per PAA/PEI molecule). When the degree of ionization is low, the cross-plane thermal conductivity of a constituent layer is higher than that of the bulk state. As the degree of ionization increases, however, the cross-plane thermal conductivity of PAA, a linear polymer, decreases because of the increase in the number of in-plane oriented polymer chains. In the in-plane direction, we investigated the heat conduction of each layer and found the enhancement of effective in-plane thermal conductivity again due to the in-plane oriented chain alignment. The heat conduction in the LbL membrane is three-dimensionally enhanced compared to those in the bulk states of the constituent polymers because of the electrostatic interactions in the cross-plane direction and the molecular alignment in the in-plane direction.

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Section: Introductionmentioning

confidence: 99%

Cross-Plane and In-Plane Heat Conductions in Layer-by-Layer Membrane: Molecular Dynamics Study

et al. 2020

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“…where R is the total ITR of PBG, R i is the thermal resistance of each sp 3 bond, n is the number of sp 3 bonds formed across the interlayer, and R VDW is the thermal resistance caused by the vdW force. Because the heat-transfer efficiency of covalent interaction is much large than that of vdW force, 37 and the vacancy is much smaller than the overlapping area, the variety of R VDW in PBG with different vacancies is ignored. Here, R VDW was equal to 80.32 Â 10 À9 m 2 KW À1 , which is the ITR of pure bilayer graphene with an overlapping area of 15.451 nm 2 .…”

Section: Influence Of Interlayer Sp 3 Bonds Formed By Adjacent Vacanc...mentioning

confidence: 99%

Effects of vacancy defects on the interfacial thermal resistance of partially overlapped bilayer graphene

Wang

Cao

Shao

et al. 2022

Phys. Chem. Chem. Phys.

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“…Associated with the miniaturization of integrated electronics, the surface-to-volume ratio of TIM increases, and the interfacial thermal resistance becomes dominant. This fact raised the focus on the application of surface modification − and surfactant additives to decrease the thermal resistance at the TIM–substrate contact. We focus on the latter in the present study.…”

Section: Introductionmentioning

confidence: 99%

“…The mechanism of adsorption is an important factor in selecting these models. Recently several studies confirmed that using thiol-terminated additives to modify Au surface by forming S–Au covalent bonds dramatically improves the Au–organic solvent interfacial heat transfer. ,,,, However, the formation of covalent bonds between the solid and adsorbent makes it hard to repair the adsorption film if damaged. Another possibility is hydrogen bonding, which is weaker than a S–Au chemical bond.…”

Section: Introductionmentioning

confidence: 99%

Molecular Dynamics Study on the Effect of Long-Chain Surfactant Adsorption on Interfacial Heat Transfer between a Polymer Liquid and Silica Surface

et al. 2020

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The addition of surfactants to polymer-based thermal interface materials applied to improve the heat dissipation efficiency of chip surfaces in contact has attracted attention for the microelectronic processing technology. In the present study, the mechanism by which a long-chain surfactant affects heat transfer across the interface between solid surface and polymer liquid was investigated by non-equilibrium molecular dynamics simulation. We constructed a system where tetracosane was used as a solvent and contained alcohol molecules as a surfactant, and they were placed between two flat silica surfaces under a thermal gradient. The effect of the hydrophilicity of silica surface, the concentration of the surfactant, and chain length of the surfactant on silica–liquid interfacial thermal resistance R b were examined. Alcohol surfactant molecules preferred to adsorb onto the hydrophilic silica (Si–OH) surface due to hydrogen bonding between alcohol and silanol hydroxyl groups. It was found that R b reduced not only with the adsorption amount of alcohol molecules but also with the chain length of alcohol. The van der Waals interaction contribution was dominant for solid–liquid and liquid–liquid heat conduction near the interface. The hydroxyl terminals of alcohol molecules were vertically adsorbed onto the Si–OH surface due to hydrogen bonds, which produced a heat path from silanols to the hydroxyl groups of alcohol. Furthermore, heat was also exchanged between alcohol hydroxyl and alkyl groups via intramolecular interaction and between the alcohol alkyl groups and nearby solvent molecules via van der Waals (vdW) intermolecular interaction. This resulted in an efficient heat path from solid surface silanols to liquid bulk. As the alcohol chain length increased without changing the number of adsorbed alcohol molecules, the heat transfer through this heat path increased, which led to a decrease in R b. These results provided insight toward the guiding principle for the molecular design of complex surfactants to enhance the interfacial heat transfer.

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A molecular dynamics study on heat conduction characteristics inside the alkanethiolate SAM and alkane liquid

Cited by 38 publications

References 46 publications

Cross-Plane and In-Plane Heat Conductions in Layer-by-Layer Membrane: Molecular Dynamics Study

Cross-Plane and In-Plane Heat Conductions in Layer-by-Layer Membrane: Molecular Dynamics Study

Effects of vacancy defects on the interfacial thermal resistance of partially overlapped bilayer graphene

Molecular Dynamics Study on the Effect of Long-Chain Surfactant Adsorption on Interfacial Heat Transfer between a Polymer Liquid and Silica Surface

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