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

Abstract

The proper design and synthesis of molecular junctions for the purpose of establishing percolative networks of conductive nanoparticles represent an opportunity to develop more efficient thermallyconductive nanocomposites, with several potential applications in heat management. In this work, theoretical classical molecular dynamics simulations were conducted to design and evaluate thermal conductance of various molecules serving as thermal bridges between graphene nanosheets. A wide range of molecular junctions was studied, with a focus on the chemical structures that are viable to synthesize at laboratory scale. Thermal conductances were correlated with the length and mechanical stiffness of the chemical junctions. The simulated tensile deformation of the molecular junction revealed that the mechanical response is very sensitive to small differences in the chemical structure. The analysis of the vibrational density of states provided insights into the interfacial vibrationalproperties. A knowledge-driven design of the molecular junction structures is proposed, aiming at controlling interfacial thermal transport in nanomaterials. This approach may allow for the design of more efficient heat management in nanodevices, including flexible heat spreaders, bulk heat exchangers and heat storage devices.©2019. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/

Molecular Junctions Enhancing Thermal Transport within Graphene Polymer Nanocomposite: A Molecular Dynamics Study

“…This value may be considered representative of a network of graphene flakes fully joined by acene junctions within a PDMS matrix and represents a theoretical upper value for molecularly joined graphene-based nanocomposites. While the thermal conductance calculated for the different PDMS embedded molecular junctions suggest large differences in their effectiveness, the conductance trend appears coherent with conductance values reported for self-standing junctions [19]. However, splitting the contribute in thermal transport from the PDMS chains and the molecular junctions is not trivial, because the calculated thermal conductance are dependent on the layout, in particular for the different heat transfer areas, a parameter that cannot be accurately quantified in molecules.…”

“…COMPASS is a Class-2 force field which provides a detailed representation of bond and non-bond interaction for soft matter and it has already been used for PDMS in thermal applications [34]. The COMPASS force field was also used for the whole system due to the primary bonding between graphene and molecular junctions, based on our previous work [19,22]. The msi2lmp tool included in LAMMPS package was used to produce the input data files with corresponding atomic interactions on the basis of COMPASS force field.…”

“…Three different molecular structures were selected in this work as junctions between the graphene foils and compared with the unjointed graphene. We choose the three molecules based on the results from our previous studies where we screened some chemically feasible [22] thermal linkers without any polymer interaction [19]. In this work, the first case study is the unjointed model made of two graphene platelets-it was designed to represent the typical contact between graphene flakes and the surrounding polymer matrix, and it is referred as "No Linkers" (Figure 3A).…”

“…A TBC increase and a reduction in thermal jump across the junction were generally described. More recently, the effect of chain length and chemical structure of molecular junctions on their thermal conductance was systematically studied, both via Molecular Dynamics (MD) and Density Functional Theory (DFT) [19,20]. Experimental investigation of molecular junctions was also explored.…”

Molecular dynamics study of convective heat transfer mechanism in a nano heat exchanger

“…17 When the system size further deceases to the nanoscale, the experimental measurement is limited and the molecular dynamics simulation is an available research technique as long as the accurate atomic interaction parameters can be guaranteed. [18][19][20] By performing MD simulation, Markvoort et al rstly came up with a thermal pump method to simulate the convective heat transfer in nanochannels. 21 Different from applying the external force to the whole uid which would bring the impractical energy into the uid domain, they only drove the uid and controlled the uid temperature in specic regions.…”