Electrically Insulating Ladder-Type Conjugated Polymer with High Thermal Conductivity

Achieving high thermal conductivities and low electrical conductivities in polymers has been a long-standing challenge that involves molecular and process engineering. Here, we present a simple approach by utilizing the nearly long-forgotten benzobisimidazopyrroloisoindoledione (BPL) ladder-type conjugated polymer. The inherent high possibility of cross-conjugation in BPL imparts the electrical insulating property, while the highly rigid and planar ladder polymer backbone facilitates efficient phonon transport, as observed from its high in-plane thermal conductivity of 27.05 ± 1.23 W m–1 K–1. Moreover, our improved synthesis for BPL enables its high solubility in formic acid, as compared to the insoluble cross-linked polymer synthesized via literature routes. The BPL synthesized using our method can be easily solution-processed from formic acid and only requires a fairly low annealing temperature of 150 °C. These make BPL a very attractive polymer for thermal management applications.