Weak interactions-driven preparing negative Poisson's ratio biobased polyimide aerogels without chemical crosslinking

Polyimide aerogels (PIAs) are increasingly favored in weight-sensitive applications such as aerospace exploration due to their exceptional elasticity, high porosity, and stability under extreme cryogenic conditions. However, the mismatch between high porosity and mechanical properties in PIAs often leads to a loss of backbone support functionality. To address this challenge, differentiated hydroxylated daidzein-based polyimides (PIs) were designed as the macromolecular chain frameworks. By leveraging hydrogen bonding interactions between the solvent and hydroxyl groups, combined with a frozen DMSO crystal growth-driven strategy, a PIA with highly ordered pore structures was successfully constructed. The PIA exhibits a hexagonal-like architecture, a negative Poisson's ratio (-0.35), elevated energy dissipation (270.04 kJ/m³), and broad damping peaks. Additionally, its bi-directional structure achieves a lower thermal conductivity of 24 mW·m^-1·K^-1, enabling the surface temperature to remain at only 95 °C even after being heated to 200 °C for 20 min. Remarkably, it can withstand stresses up to 250 kPa at 95 % transverse compression. A pressure sensor fabricated from this polymer showed rapid response and recovery times of 0.48 and 0.60 s, respectively, illustrating its suitability for flexible pressure sensing applications. This work highlights that using PI with multiple chemical reaction sites is a convenient and feasible approach for constructing shock-absorbing bio-based polymer materials with integrated pressure conduction, monitoring, and thermal insulation capabilities.