Facile synthesis of macroporous zwitterionic hydrogels templated from graphene oxide-stabilized aqueous foams

Conventional strategies based on emulsion templates to produce porous materials are complicated and not environmental-friendly, thus inspiring a facile and novel approach via polymerization of aqueous foams. Graphene oxide (GO) has been proved as a very efficient Pickering stabilizer for oil-in-water or water-in-oil emulsions, however, it has rarely (if any) been used to stabilize aqueous foams. It is of high interest to prepare GO-stabilized aqueous foams and subsequent porous hydrogels after polymerization of the aqueous phase.

GO was slightly hydrophobized with cetyltrimethylammonium bromide (CTAB) and then used to stabilize aqueous foams containing a water-soluble monomer, N-(3-Sulfopropyl)-N-methacroyloxyethyl-N,N-dimethylammonium betaine (SBMA). After polymerizing the aqueous phase, macroporous zwitterionic hydrogels (PSBMA) were prepared. The pore morphology of macroporous PSBMA were observed by a field-emission scanning electron microscope.

The wettability of modified GO by both water and air, indeed has a significant influence on the air bubble size and size distribution as well as the pore size of resulting macroporous PSBMA hydrogels. The pore size and pore interconnectivity of the hydrogels can be tailored by simply varying the surface property and concentration of GO in water. PSBMA hydrogels exhibit a pronounced uptake of aqueous NaCl solutions and efficient separation of oil-in-water emulsions.