Oleo-sheets and omni-sheets: Fabric-like superabsorbers for oil, water, or any solvent

Abstract

Materials that can selectively absorb oil from water could be used to clear oil spills, but such absorbents are typically either in the form of powders or small, bulky solids. In homes and labs, spills of oil are absorbed with cloth or paper towels, which are flexible and foldable, but exhibit poor absorbency. There is hence a need for fabric-like sheets that can absorb considerable oil, and here, we report the synthesis of such oleo-sheets by templating organofoams. A foam of CO2 bubbles in a water-in-oil emulsion is first created, with the bubbles stabilized by a silicone surfactant. Monomers in the oil phase (alkyl and urethane acrylates) are then polymerized rapidly at room temperature to give a porous gel. By ambient drying this gel, we make oleo-sheets (∼10 × 7 × 0.4 cm in size) and oleo-sponges (size ∼2 × 2 × 1 cm), which are both soft, pliable materials with interconnected pores. These materials are hydrophobic (water contact angle ∼130°) and they selectively absorb a range of oils (organic solvents) from water. Their absorption capacity (> 50 g/g) exceeds that of commercial absorbents like polyurethane sponges or cloth pads. We also make a magnetic oleo-sponge – after such a sponge absorbs oil, it can be lifted up by a magnet. Lastly, we create an omni-sheet with two distinct sides, one that selectively absorbs oil while the other does the same for water. Thus, the omni-sheet can pick up any spilled liquid. The materials reported here are likely to find application in cleaning up spills due to their unique combination of convenient form factor, robust mechanical properties, and excellent absorbency. Moreover, our synthesis technique can be easily scaled up as it is simple and energy-efficient (since it does not involve freeze-drying) and environment-friendly.