Naphthalene-Modified Cationic Initiators for Superior Polymerization Stability and Thermal Conductivity in Epoxy...

Naphthalene-modified cationic initiators with tunable counteranions were developed to extend the epoxy curing lifetime, enabling the efficient formation of high-ordered networks in both conventional and liquid crystalline (LC) epoxy systems. The extended lifetime of these initiators allows the LC epoxies to maintain their inherently ordered structure during network formation, which is essential for efficient phonon transport. Differential scanning calorimetry demonstrated a broader exothermic peak width and a more uniform heat release profile, confirming controlled and efficient polymerization. X-ray diffraction analysis further demonstrated that the π-π stacking peak characteristic of the LC domains was clearly preserved, indicating that the mesogenic order was maintained after curing. Consequently, the cured LC epoxies exhibited a remarkably high thermal conductivity of 0.86 W m^-1 K^-1. This is one of the highest reported for unfilled organic systems. Adding hexagonal boron nitride (h-BN) filler further enhanced heat transfer, reaching 25.08 W m^-1 K^-1 at 85 wt%. These results demonstrate that rational initiator design with long-term operation and controlled polymerization provides a simple strategy for fabricating high-purity, thermally conductive, and reprocessable epoxy networks for advanced thermal management applications.