The effect of the block ratio on the thermal conductivity of amorphous polyethylene–polypropylene (PE–PP) diblock copolymers

Abstract

Block copolymers have a wide range of applications, such as battery electrolytes and nanoscale pattern generation. The thermal conductivity is a critical parameter in many of these applications (e.g., batteries), which is strongly related to the molecular conformation. In this work, the thermal transport in a representative diblock copolymer, polyethylene (PE)–polypropylene (PP), at different PE to PP block ratios is studied using molecular dynamics (MD) simulations. Our results show that the thermal conductivity of the PE–PP diblock copolymer can be tuned continuously by the block ratio, and it is strongly related to the molecular conformation, characterized by the radius of gyration (R_g). It is found that increasing the PP portion results in an overall decreasing trend in the thermal conductivity since the PP block has a more flexible backbone, which leads to a smaller spatial extension of the whole PE–PP copolymer molecule. Thermal conductivity decomposition shows that the bonding contribution is dominant in both the PE and PP portions of the block copolymer. The findings from this study can help understand thermal transport in general block copolymers.