Epoxy resins with enhanced thermal conductivity are in great demand to improve the thermal management of electrical motors. However, the thermal conductivity of epoxy resin is typically low, comparable to 0.2 W/(m K), and a predictive understanding of the connection between molecular structure and thermal conductivity is not yet established. In this work, we present data for the thermal conductivity of seven thermosets synthesized from one commercially available diepoxide (resorcinol diglycidyl ether) and seven phenylenediamines to systematically examine the dependence of thermal conductivity on the molecular structure of the phenylenediamine hardener. Variations in the molecular structure of phenylenediamines, for example, positions of amine groups and the addition of an electron-withdrawing group, produce up to a factor of 2 change in the thermal conductivity of the cured resins. The highest thermal conductivity of 0.27 W/(m K) is obtained with 5-chloro-m-phenylenediamine; the lowest thermal conductivity of 0.14 W/(m K) is obtained with o-phenylenediamine. Thermal conductivities of these seven epoxy resins are 10−40% lower than the prediction of the minimum thermal conductivity model.

High thermal conductivity polymers are in great demand as thermal management materials. However, the thermal conductivity of polymers is typically low, ∼0.2 W/(m K), and a predictive understanding of the relationship between the thermal conductivity and the molecular structure of polymers is not yet established. In this work, 14 epoxy resin thermosets are synthesized from one aliphatic epoxide and one aromatic epoxide with seven amine hardeners. These thermosets are used to systematically examine the dependence of the thermal conductivity on the molecular structure of the epoxide and the hardener. In general, aromatic structures have a higher thermal conductivity than aliphatic structures. Moreover, naphthalene-based hardeners provide the highest thermal conductivity, 0.34 W/(m K), 230% higher than the lowest thermal conductivity among the 14 epoxy resin thermosets. The cross-linking density is controlled by mixing different molar ratios of diamine and triamine and does not influence the thermal conductivity, volumetric heat capacity, density, or longitudinal speed of sound. Measured thermal conductivities of 14 epoxy resins lie between 50 and 115% of the prediction of the minimum thermal conductivity model.

Polymers with enhanced thermal conductivity are in great demand for thermal management of electronic devices. However, the thermal conductivity of polymers is typically low (∼0.2 W/(m K)). In this work, four epoxy resins were cured using one commercial diepoxide and four diamine hardeners with an anthraquinone structure. The thermal conductivity of one epoxy resin reached 0.52 W/(m K), which is ∼2.5 times that of common polymers. These epoxy resins are shown to have a semicrystalline structure, and both the thermal conductivity and density of the four epoxy resins exhibited a positive correlation with crystallinity.

Rapid developments in high-performance computing and high-power electronics are driving needs for highly thermal conductive polymers and their composites for encapsulants and interface materials. However, polymers typically have low thermal conductivities of ∼0.2 W/(m K). We studied the thermal conductivity of a series of epoxy resins cured by one diamine hardener and seven diepoxide monomers with different precise ethylene linker lengths ( x = 2–8). We found pronounced odd–even effects of the ethylene linker length on the liquid crystalline order, mass density, and thermal conductivity. Epoxy resins with even x have liquid crystalline structure with the highest density of 1.44 g/cm 3 and highest thermal conductivity of 1.0 W/(m K). Epoxy resins with odd x are amorphous with the lowest density of 1.10 g/cm 3 and lowest thermal conductivity of 0.17 W/(m K). These findings indicate that controlling precise linker length in dense networks is a powerful route to molecular design of thermally conductive polymers.

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.