Thermal conductivity of bottle-brush polymers

Abstract

Using molecular dynamics (MD) simulations of a generic model, we investigate heat propagation in bottle--brush polymers (BBP). An architecture is referred to as a BBP when a linear (backbone) polymer is grafted with the side chains of different length $N_{\mathrm{s}}$ and grafting density ${\rho }_{\mathrm{g}}$, which control the bending stiffness of a backbone. A BBP is of particular interest due to two competing mechanics: increased backbone stiffness, via $N_{\mathrm{s}}$ and ${\rho }_{\mathrm{g}}$, increases the thermal transport coefficient $\kappa$, while the presence of side chains provides additional pathways for heat leakage. We show how a delicate competition between these two effects controls $\kappa$. These results reveal that going from a weakly grafting (${\rho }_{\mathrm{g}}<1$) to a highly grafting (${\rho }_{\mathrm{g}}\ge 1$) regime, $\kappa$ changes non--monotonically that is independent of $N_{\mathrm{s}}$. The effect of side chain mass on $\kappa$ and heat flow in the BBP melts are also discussed.