Reduced thermal conductivity in molecular forests

Heat propagation in quasi-one dimensional materials (Q1DMs) often appears paradoxical. While an isolated Q1DM, such as a nanowire, carbon nanotube, or polymer, can exhibit a high thermal conductivity \k{appa}, forests of the same materials show a reduction in \k{appa}. Here, the complex structures of these assemblies have hindered the emergence of a clear molecular picture of this intriguing phenomenon. We combine multiscale (coarse-grained) simulation with the concepts known from polymer physics and thermal transport to unveil a generic (microscopic) picture of \k{appa} reduction in molecular forests. We show that a delicate balance between the bond orientations, the persistence length of the Q1DM and the flexural vibrations govern the knock-down of \k{appa}.