  Proper design and manufacturing thermal bridges based on molecular junctions
at the contact between graphene platelets or other thermally conductive
nanoparticles would provide a fascinating way to produce efficient heat
transport networks for the exploitation in heat management applications. In
this work, using Non Equilibrium Molecular Dynamics, we calculated thermal
conductance of alkyl chains used as molecular junctions between two graphene
nanoribbons, both as covalently bound and Van der Waals interdigitated chains.
Effect of chain length, grafting density, temperature and chain interdigitation
were systematically studied. A clear reduction of conductivity was found with
increasing chain length and decreasing grafting density, while lower
conductivity was observed for Van der Waals interdigitated chains compared to
covalently bound ones. The importance of molecular junctions in enhancing
thermal conductance at graphene nanoribbons contacts was further evidenced by
calculating the conductance equivalence between a single chain and an
overlapping of un-functionalized graphene sheets. As an example, one single
pentyl covalently bound chain was found to have a conductance equivalent to the
overlapping of an area corresponding to about 152 carbon atoms. These results
contribute to the understanding of thermal phenomena occurring within networks
of thermally conductive nanoparticles, including graphene nanopapers and
graphene-based polymer nanocomposites, which are or high interest for the heat
management application in electronics and generally in low-temperature heat
exchange and recovery.
