Decreased Thermal Conductivity of Polyethylene Chain Influenced by Short Chain Branching

TL;DR

This study uses molecular dynamics simulations to show that short chain branches in polyethylene significantly reduce its thermal conductivity, with heavier branches causing greater decreases, providing insights for designing low-thermal-conductivity polymers.

Contribution

It demonstrates how short chain branching, especially heavier branches, can effectively lower polyethylene's thermal conductivity, a novel insight for polymer thermal management.

Findings

Branching decreases thermal conductivity of PE.

Thermal conductivity saturates at about 40% of pristine PE with increased branch density.

Heavy branches cause a greater reduction in thermal conductivity.

Abstract

In this paper, we have studied the effect of short branches on the thermal conductivity of a polyethylene (PE) chain. With a reverse non-equilibrium molecular dynamics method applied, thermal conductivities of the pristine PE chain and the PE-ethyl chain are simulated and compared. It shows that the branch has a positive effect to decrease the thermal conductivity of a PE chain. The thermal conductivity of the PE-ethyl chain decreases with the number density increase of the ethyl branches, until the density becomes larger than about 8 ethyl per 200 segments, where the thermal conductivity saturates to be only about 40% that of a pristine PE chain. Because of different weights, different types of branching chains will cause a different decrease of thermal conductivities, and a heavy branch will leads to a lower thermal conductivity than a light one. This study is expected to provide some fundamental guidance to obtain a polymer with a quite low thermal conductivity.