Thermal Conductivity in Crystalline Polythiophene Using ab-initio Anharmonic Lattice Dynamics

Bulk polymers typically have poor thermal conductivity, but the intrinsic thermal conductivities of polymer chains and crystals can be very high, exceeding those of many metals. Recent measurements have shown that even semi-crystalline polymers with complex unit cells still achieve high thermal conductivity, contrary to the typical guidelines for effective thermal transport which prescribe a simple unit cell with a small number of atoms. In this work, we explore the thermal conductivity and three-phonon scattering pathways of polythiophene using anharmonic lattice dynamics with ab-initio, finite temperature force constants. Lattice dynamics allows us to look in detail at the scattering phase space and three-phonon interaction strength for each individual mode, to identify which vibrations contribute most to thermal conductivity and why. Knowledge of the physical features which determine the thermal transport aids in establishing molecular-scale design principles for thermally conductive polymers.