Here we have obtained a thermoresponsive three-dimensional (3D) polyurethane (PU) sponge with temperature-controlled superwettability. First, silanization was used to enhance the surface roughness of the PU sponge and reactive vinyl groups were provided. We then grafted a polyisopropylacrylamide (PNIPAAm) hydrogel to the PU skeleton, resulting in the preparation of a temperature-responsive 3D PU material showing useful oil−water separation performance. The surface morphology, chemical composition, and wettability of the prepared modified PU sponge were clarified. The surface wettability of the modified sponge changed with temperature. Under ambient conditions with a temperature of 25 °C, which is lower than the low critical solution temperature of PNIPAAm (LCST, about 32 °C), the product showed superhydrophilicity in air and superoleophobicity under water, while when the outside temperature (45 °C) became higher than the LCST, the product changed to show high hydrophobicity in air and superlipophilicity under water. After 8 cycles of temperature variation, the product still showed impressive responsiveness. In addition to the smart responsive properties, the modified PU sponge could absorb and automatically desorb oil at 45 and 20 °C, respectively, showing good oil−water separation ability, together with the capability of oil recycling.

A versatile approach to synthesis of hydrophobic polymeric cryogels is proposed using acetic acid crystals instead of ice crystals as porogen through cryo‐polymerization. In the range of 60 to 90 vol% of acetic acid, polymerization at ambient temperature gives rise to particulate polymers in beaded or amorphous shape, while polymerization at 4 °C, lower than the melting point of acetic acid (16.6 °C), leads to the formation of cryogel‐like monoliths with supermacroporous structure, which is mainly ascribed to cryo‐concentration effect. According to the measurements by scanning electron microscopy and mercury intrusion porosimetry, the dried samples are supermacroporous with pore size mainly ranging from several micrometers to several hundred micrometers, which can be feasible for rapid mass transfer. The forming cryogels display a superfast responsiveness to organic solvents, possibly stemming from their supermacroporosity and distinctive hydrophobicity.

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