Recyclable microcellular rubber foams with superior photothermal performance via constructing Fe3+ heterodentate coordination between epoxidized natural rubber and polyaniline†

Developing recyclable microcellular rubber foams with excellent photothermal conversion ability can reduce resource waste and harvest solar energy to alleviate environmental pollution and the energy crisis simultaneously. In this work, we propose a novel “one-stone-two-birds” strategy: the construction of Fe³⁺ heterodentate coordination between epoxidized natural rubber and polyaniline was successfully confirmed by FT-IR, XPS, and Raman spectroscopy. Through supercritical CO₂ foaming technology, recyclable microcellular epoxidized natural rubber/polyaniline/FeCl₃ foams (f-EPx) with excellent photothermal conversion were first fabricated and reprocessed. Changing the temperature and FeCl₃ content could control the viscoelasticity, subsequently regulating cell size (4.4–9.0 μm) and foam tensile properties (elongation at break up to 710%). The recycling of f-EPx was realized through “cutting-molding-foaming” cycles. After 4 cycles of processing, the 4th reprocessed f-EPx still possessed an intact cell structure with 400% elongation at break. Remarkably, Fe³⁺ heterodentate coordination enabled f-EPx to harvest 92.6% photothermal conversion efficiency and a 90.5% shape recovery ratio by photo-triggered shape memory effects. Strikingly, the bird egg wrapped by an f-EPx film could be cooked thoroughly under near-infrared light for only 15 minutes, exhibiting potential applications as photo-heating sleeves in solar energy harvesting. This work provides an innovative strategy for fabricating recyclable microcellular rubber foams for clean energy utilization, envisioning the sustainable development of the rubber industry.