Atomistic insights into the effect of polymerization on the thermophysical properties of 2-D C₆₀ molecular solids

The ability to polymerize solid-state C₆₀ molecular crystals via intermolecular covalent bond formation provides controllable routes to obtaining structures with tunable mechanical and thermal properties. In this regard, using molecular dynamics simulations, fundamental insights into the interplay between degree of polymerization and the ensuing evolution in the thermophysical properties of C₆₀ polymorphs are obtained for the first time. In particular, it is unambiguously shown that 2-D polymerized C₆₀ polymorphs show a two order of magnitude enhancement in the thermal conductivity and one order of magnitude change in the elastic stiffness. The significant increase in the thermal conductivity is correlated to the presence of new THz thermal phonon modes, characterized by larger mean free paths. In addition, it is also seen that the Debye temperature of the C₆₀ structures is strongly dependent on the extent of polymerization. The new understanding obtained in this work provides valuable guidelines for the design and development of new C₆₀ based phononic metamaterials for applications as vibrational and thermal management systems.