Recyclable microcellular rubber foams and 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 the environmental pollution and energy crisis simultaneously. In this work, we propose a novel “one-stone-two-birds” strategy: the constructure of Fe3+ heterodentate coordination between epoxidized natural rubber and polyaniline were successfully confirmed by FT-IR, XPS, and Raman. 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 intact cell structure with 400% elongation at break. Remarkably, Fe3+ heterodentate coordination endowed f-EPx to harvest 92.6% photothermal conversion efficiency and 90.5% shape recovery ratio by photo-triggered shape memory effects. Strikingly, the bird egg wrapped by 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 to fabricating recyclable microcellular rubber foams for clean energy utilization, envisioning the sustainable development of rubber industry.