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.

Four polymerized ionic liquids (PILs) were systematically designed to study the effect of polymer architecture and linker polarity on ion aggregation and transport. Specifically, linear and network PILs with the same ammonium cations (Am) and bis­(trifluoromethane)­sulfonimide (TFSI) anions were prepared by step-growth polymerization, and polarity was tuned by incorporating two precise linkers, either polar tetra­(ethylene oxide) (4EO) linker or nonpolar undecyl (C11) linker. The glass transition temperature (T g) substantially increased with the nonpolar C11 linker or upon cross-linking to form a network. The low wave-vector (q) ion aggregation peak from wide-angle X-ray scattering (WAXS) was not observable in the linear 4EO PIL, while it was most pronounced in the network C11 PIL. The network C11 PIL exhibited the strongest decoupling, where the ionic conductivity at T g is greater than 1 order of magnitude higher than the other PILs. This systematic comparison suggests that network structure and nonpolar linkers can promote both ion aggregation and ionic conductivity close to T g.

Network architectures reveal odd–even effects in existing PIL systems.

Vitrimers, dynamic polymer networks with topology conserving exchange reactions, can lead to unusual evolution of the melting temperature and crystal structure of ethylene networks.