Abstract: Rapid cleanup and easy recovery of spilled heavy oils is always a great challenge due to their high viscosity (> 10³ mPa s). One of the efficient methods to absorb highly viscous oils is to reduce their viscosity by increasing their temperature. In this work, we integrate the sunlight-induced light-to-heat conversion effect of polypyrrole (PPy) and thermo-responsive property of poly(N-isopropylacrylamide) (PNIPAm) into the melamine sponge, which successfully delivers a fast heavy oil absorption under sunlight and passive oil release underwater at room temperature. Thanks to the rationally designed functionalities, the PNIPAm/PPy functionalized sponges possess oleophilicity and hydrophobicity under sunlight. Due to the photo-thermal effect of PPy, the sponges locally heat up contacting heavy oil under sunlight and reduce its viscosity to a point where the oil voluntarily flow into the pores of the sponge. The material in this work is able to rapidly absorb the heavy oil with room temperature viscosity as high as ~1.60 × 10⁵ mPa s. The absorbed oil can be passively forced out the sponge underwater at room temperature due to the hydrophilicity of PNIPAm. The sunlight responsive and multifunctional sponge represents a meaningful attempt in coming up with a sustainable solution towards heavy oil spill.

https://onlinelibrary.wiley.com/doi/abs/10.1002/admi.201800412