Thermal conductivity of polymers: A simple matter where complexity matters

TL;DR

This paper reviews recent advances in understanding and tuning the thermal conductivity of polymers, highlighting the complexity and importance of molecular structure in controlling heat transfer properties.

Contribution

It provides a comprehensive overview of computational, theoretical, and experimental findings on polymer thermal conductivity and discusses future research directions.

Findings

Polymer thermal conductivity is generally low, around 0.4 W/Km.

Energy transfer in polymers depends on bonded connections and molecular structure.

Recent engineering efforts aim to tune thermal conductivity through macromolecular design.

Abstract

Thermal conductivity coefficient $\kappa$ measures the ability of a material to conduct a heat current. In particular, $\kappa$ is an important property that often dictates the usefulness of a material over a wide range of environmental conditions. For example, while a low $\kappa$ is desirable for the thermoelectric applications, a large $\kappa$ is needed when a material is used under the high temperature conditions. These materials range from common crystals to commodity amorphous polymers. The latter is of particular importance because of their use in designing light weight high performance functional materials. In this context, however, one of the major limitations of the amorphous polymers is their low $\kappa$, reaching a maximum value of about 0.4 W/Km that is 2--3 orders of magnitude smaller than the standard crystals. Moreover, when energy is predominantly transferred through the bonded connections, $\kappa \ge 100$ W/Km. Recently, extensive efforts have been devoted to attain a tunability in $\kappa$ via macromolecular engineering. In this work, an overview of the recent results on the $\kappa$ behavior in polymers and polymeric solids is presented. In particular, computational and theoretical results are discussed within the context of complimentary experiments. Future directions are also highlighted.