Highly efficient thermal insulation polyimide foams enhanced by cation-π interactions

Advanced thermal management materials play a crucial role in driving innovation and enhancing the performance of cutting-edge technologies. In this work, polyimide foams were fabricated by freeze-drying precursor polyamic acid (PAA) solutions and thermally imidization, incorporating π-electron-rich benzimidazole structures along with Cu²⁺, Ca²⁺, Na⁺, and K⁺ ions to form cation-π crosslinked structures. The integration of cation-π crosslinked structures notably enhanced polyimide foams, boosting its compressive strength, glass transition temperature, and thermal insulation properties. Particularly noteworthy was the superior enhancement and modification effects exhibited by Ca²⁺ among the cations, followed by Cu²⁺, whereas Na⁺ and K⁺ showed relatively lesser effectiveness. Specifically, the inclusion of 30 mol% Ca²⁺ resulted in a remarkable 136.36% increase in compressive strength and a 320.47% increase in Young's modulus for the polyimide foams. Furthermore, a 50 mol% infusion of Ca²⁺ reduced the thermal conductivity from 0.0533 to 0.0432 W m⁻¹ K⁻¹ compared to pristine polyimide foam, while also decreasing the surface temperature of a 15 mm thick sample from 74.1 to 55.7 °C after exposure to a 200 °C platform for 10 min. This study underscores the importance of integrating cation-π crosslinked structures into polyimide foams, leading to significant improvements in thermal insulation properties and thus advancing the field of thermal management materials.