The rapid development of photopolymerization technologies in cutting-edge fields such as microelectronics, additive manufacturing, and flexible electronics has created an urgent demand for advanced photoresins that combine exceptional mechanical strength with ultrahigh thermal stability. To address this challenge, we present a random allyl functionalization strategy to impart photoprocessability to polybenzimidazole (PBI). Starting from commercially available diacid and tetraamine monomers, we first synthesize poly(ether-benzimidazole) (OPBI), followed by statistical grafting of allyl groups onto the backbone nitrogen sites through controlled reaction with 3-bromopropene, where the degree of substitution is tuned by adjusting the stoichiometric ratio of sodium hydride (NaH) to the alkylating agent. This approach yields a series of allyl-functionalized OPBIs (AOPBIs) with targeted grafting levels of 0%, 25%, 50%, 75%, and 100%. Under 405 nm UV irradiation, these AOPBIs undergo efficient thiol–ene photoclick reactions with pentaerythritol tetrakis(3-mercaptopropionate) (PETMP), rapidly forming densely cross-linked covalent networks. Guided by a “sparse yet sufficient” design principle, we demonstrate that even modest functionalization enables effective photocuring while largely preserving the intrinsic high-performance characteristics of OPBI. Remarkably, the resin containing only 25% allyl substitution (Resin2) exhibits outstanding thermo-mechanical properties: a tensile strength of 176 MPa, a Young’s modulus of 2.97 GPa, and an onset decomposition temperature (Td10%) in air exceeding 488 °C, significantly outperforming existing photoprocessable high-temperature polymer systems. This work establishes that controlled yet random low-density functionalization provides an effective means to decouple photoprocessability from the inherent thermal and mechanical robustness of rigid high-performance polymers. The strategy offers a practical and scalable route to render otherwise intractable engineering polymers compatible with advanced optical manufacturing techniques, holding significant promise for applications in microelectronic encapsulation, high-resolution additive manufacturing, and flexible high-temperature devices.
Mi et al. (Mon,) studied this question.