Effects of polymer chain confinement on thermal conductivity of ultrathin amorphous polystyrene films

The thermal properties of polymers are intricately related to the structural elements. Using equilibrium molecular dynamics simulations, we study the thermal conductivity of ultrathin amorphous polystyrene films versus density,  ρ, film thickness, dz, and the ratio of thickness to the radius of gyration, dz/Rg , known as the chain confinement indicator. We find that the thermal conductivity increases linearly as dz/Rg  increases, or in other words, that stronger confinement and less entanglement lead to lower thermal conductivity. This underlines the fundamental difference in heat conduction between amorphous polymers and crystalline polymers.