Fully Recyclable Covalent Adaptable Network Composite with Segregated Hexagonal Boron Nitride Structure for Efficient Heat Dissipation

As electronics become smaller and denser in function, lighter polymer composites with high thermal conductivity (TC) have been increasingly developed as heat dissipating materials. Since the polymer matrix exhibits a vanishingly low TC compared with that of the filler, the composite TC is determined by the heat conduction pathway formed along the interconnected filler networks. In this context, a high composite TC can be obtained by increasing the filler loading up to the maximum filler packing limit. However, a tradeoff between the composite weight and TC prohibits a constant increase in the filler loading. To this end, a highly networked but heat-processable poly(beta-amino ester) covalent adaptable network (CAN) based on catalyst-free transesterification and a dynamic aza-Michael reaction is synthesized as a matrix to realize both a high composite TC and low density. Owing to the unique malleable characteristic of the CAN, conductive filler networks (or a segregated filler structure) are formed along the CAN domain interfaces upon simple heat-pressing a powder mixture of the CAN and hexagonal boron nitride (hBN). The resulting composite exhibits an exceptionally high TC of 13.5 W/mK at a low density of 1.75 g/ cm3. The TC value corresponds to 197% of an identical CAN composite but with randomly dispersed hBN. To further highlight the versatility of the CAN matrix, ecofriendly composite recycling through reprocessing along with filler recovery by depolymerizing the matrix in heated water without using any external catalysts is also demonstrated.