Dynamic Covalent Bonds in Vitrimers Enable 1.0 W/(m K) Intrinsic Thermal Conductivity

Abstract

Polymers are under increasing demand as thermal management materials for electronic devices such as integrated circuits and electrical machines. However, the intrinsic thermal conductivity of polymers is typically low, around 0.2 W/(m K). Although crystallinity is qualitatively known to have a positive correlation with thermal conductivity, the quantitative relationship is unclear because, in most cases, changes in crystallinity are accompanied by differences in the chemical structure of the polymer. In this work, vitrimers with a fixed chemical structure and slow crystallization kinetics are investigated to reveal the relationships between crystallinity and various physical properties relevant to heat transport. As slow crystallization occurs over the span of one week, the physical properties of the vitrimers also evolve. Changes in thermal conductivity are dramatic from 0.10 to 1.0 W/(m K). Quantitative relationships among crystallinity, thermal conductivity, speed of sound, and chain conformation are elucidated by a combination of in situ measurements.