Sequential interpenetrating polymer networks decoupling pore interconnectivity and mechanical resilience in polyimide/polybenzoxazine aerogels for robust oil-water separation

A sequential IPN strategy decouples pore connectivity from mechanical resilience. • Rigid PBOZ nodes enable extraordinary cyclic resilience at 80% strain. • Robust superhydrophobic aerogels achieve ultrafast oily emulsion separation Polymer aerogels for oil-water separation often need to combine high pore interconnectivity with stable elastic recovery under cyclic compression, yet these requirements are rarely compatible in conventional polyimide (PI) networks. A room−/high-temperature sequential interpenetrating polymer network (IPN) strategy is introduced to decouple pore formation from mechanical locking. Poly(hexahydrotriazine) (PHT) forms in situ at room temperature, acting as a flexible bridging network that disrupts PI lamellar stacking and induces three-dimensional pore interconnectivity. Subsequent high-temperature curing of benzoxazine (BOZ) generates rigid polybenzoxazine (PBOZ) nodes that stabilize stress distribution and enhance elastic recovery without sealing pore throats. Pure PI aerogels exhibit poor connectivity and limited resilience, while PI/PBOZ/PHT aerogels show hierarchical interconnected pores (3–15 μm) with reduced shrinkage. Mechanistically, PHT promotes interfacial coupling and suppresses interlayer slippage, while PBOZ nodes on pore walls dominate elastic recovery and mechanical stability. The optimized aerogel exhibits superhydrophobicity (water contact angle 159.1°), oil uptake of 36–70 g/g, emulsion flux up to 6971 L m −2  h −1 (>98% efficiency), only 3% stress decay after 30 cycles at 80% strain, low thermal conductivity (0.0333 W m −1  K −1 ), and high char yield (42% at 800 °C). These results demonstrate that stage-specific network formation allows for the decoupling of pore connectivity and mechanical resilience, leading to enhanced transport and mechanical properties without trade-offs. Download: Download high-res image (167KB) Download: Download full-size image