Snap-hook strategy based on dynamic boroxine networks to access 3D printing of high-performance polyimide

Polyimide (PI), a special engineering plastic, features robust mechanical properties and exceptional thermal
stability. However, its processing and molding are limited by thermal pressing, making the fabrication of high
performance customized complex 3D shapes a significant challenge. Here, we present a PI combines high per-
formance with the ability to access 3D printing and recyclability, facilitated by a snap-hook polyimide (SHPI)
strategy based on dynamic boroxine network. Capping the liner PI with phenylboronic acid, which could
reversible formation of six-membered boroxine rings occurs at both ends of the liner PI under heat and specific
solvents, resulting in dynamic crosslinked PI (DCPI) and liner SHPI. Due to the stability and high bond energy of
the boroxine, DCPI exhibits exceptional mechanical properties (tensile strength ≈ 110 MPa, Young's modulus ≈
3 GPa) and thermal performance (Tg ≈ 223 ◦C, Td ≈ 539 ◦C). The selective cleavage of boroxine bonds enables
the snap-hook functionality that allows reversible conversion between DCPI and SHPI, imparting solubility and
facilitating infinite recyclability, 3D printability, and sustainable printability, thereby achieving the creation and
elimination of high-performance PI 3D structures. Moreover, the 3D-printed PI sealing ring structure, as a
demonstration, showcases its limitless potential for applications in the aerospace industry. This work opens new
avenues for the personalized construction of high-performance engineering polymers and provides a viable
approach for the development of sustainable 3D printing.