Thermal transport in polymers: Intra- versus intermolecular energy transport

The thermal transport of polymer materials is important for various applications such as e.g. packaging. Long chain molecules provide different pathways of energy transport due to the distinct microscopic interactions, i.e., stiff, covalently bonded backbone interactions versus soft, nonbonded interactions, such as van der Waals (vdW) forces. The rate of intramolecular energy transport along the molecular backbone is higher than that of intermolecular transport. This correlation between energy-transport rate and macromolecular configuration opens opportunities for tailoring the thermal conductivity of a material.

We devise a simple model that accounts for the fast bonded and slow nonbonded, diffusive energy transport. We show how the model parameters can be quantitatively obtained from molecular simulation and validate the model by studying both, atomistic all-atom representations of polymer materials and a universal, coarse-grained model [1]. Applications to the thermal transport of lamella-forming diblock copolymers are discussed and compared to experiments that image heat flux with sub-10 nm resolution [2].