Poly(β-amino esters) (PBAEs), which include tertiary amines at the β-position of ester linkages, are promising in biomaterials due to their biodegradability and pH responsiveness. Such characteristics in the molecular structure are also appealing for designing catalyst-free covalent adaptable networks (CANs), but this has rarely been explored in the literature. Herein, we synthesize a series of PBAE-based CANs by aza-Michael addition, using diacrylate monomers with and without β-hydroxyl groups, and a triamine crosslinker. By leveraging hydrogen bonding, the thermal and mechanical properties of these PBAE-based CANs are effectively tuned through the monomer composition. Owing to the numerous tertiary amines serving as internal catalysts, these CANs undergo catalyst-free network exchange through a dynamic aza-Michael reaction. Interestingly, increasing the amount of βhydroxyl groups accelerates overall stress relaxation from the synergistic effects of transesterification (associative type) at lower temperatures and dynamic aza-Michael reaction (dissociative type) at higher temperatures. Based on these features, we successfully demonstrate the reprocessing and healing at elevated temperatures under mild pressure, as well as shape memory and shape reconfiguration. Thus, controlling the β-hydroxyl group concentration in PBAE-based CANs is a useful strategy for enhancing both the mechanical strength and reprocessing rate.

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(β-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.