Superamphiphilic Polyurethane Foams Synergized from Cellulose Nanowhiskers and Graphene Nanoplatelets

Superamphiphilic materials are attracting significant attention because of their unique affinity to both water and oil. It is generally accepted that graphene-based assemblies are hydrophobic. Here, novel superamphiphilic polyurethane (PU) foams by the synergetic effect of cellulose nanowhiskers (CNWs) and graphene nanosheets (GNs) are reported. This process involves the creation of CNWs' base coating on the surface of PU network prior to GN coatings to obtain superamphiphilic surfaces by the simple dip-coating method. Wetting behaviors of the foams start to turn from hydrophobicity into superamphiphilicity by increasing the concentration of the CNWs up to 0.5 wt%. The hydrophobicity recovers when the concentration of CNWs reaches 1.0 wt%. The superamphiphilic foam (CNWs' concentration is 0.75 wt%) exhibits high storage capacity for water and various organic solvents up to 22-24 times of its own weight. Moreover, the coated foams can be reused for absorbing liquids for more than 20 cycles without losing their superamphiphilicity, exhibiting good reusability and durability. The discovery of this superamphiphilic foam is of great significance for the development of superwetting materials and finding their applications in oil emulsions purifying and catalyst anchoring fields.