One-pot facile synthesis of PDMS/PDMAEMA hybrid sponges for surfactant stabilized O/W emulsion separation

Hydrophobic/oleophilic sponges are excellent absorbent materials for oil contaminant removal. However, the application is limited in dealing with surfactant stabilized O/W emulsions. The water in the emulsion isolates the contact between the sponge and oil droplets. Consequently, the oil absorption efficiency is not ideal. Herein, to improve the oil absorption efficiency from anionic surfactant stabilized O/W emulsions, water responsive hybrid sponges were reported. To prepare such sponges, water soluble poly(N,N-dimethylaminoethylmethacrylate) (PDMAEMA) was introduced into polydimethylsiloxane (PDMS) sponges using table salt as a template and multi-walled carbon nanotubes (MWCNTs) as mechanical reinforcement in a one-pot method. Upon contact with an O/W emulsion, the water soluble PDMAEMA chain rose to the surface of the sponge, turning the hydrophobic surface into hydrophilic. Next, the tertiary amine groups in PDMAEMA ionized in water and carried positive charges which would cause the coagulation of oil droplets. Finally, the coagulated oil droplets were absorbed immediately by the oleophilic inner part of the sponge through the wicking effect. As a result, a Janus interface was generated in situ and sustained. Such material design synergistically contributed to a satisfactory hexadecane (HD) absorption efficiency of 178 ± 4% in 25 min. In contrast, the PDMS-MWCNT_1.0% sponge could only absorb 9.8 ± 0.2% HD. Moreover, these sponges also presented robust mechanical performance and reusability, offering a new route for oil/water separation and oil pollution remediation in open water.