In situ mussel-inspired Janus membranes using catechol and polyethyleneimine as the additives for highly efficient oil/water emulsions separation

Janus membranes (JMs) with asymmetrical wettability have been fabricated by (co)deposition of dopamine and its catechol derivatives on the hydrophobic substrates for oil/water emulsions separation, while it remains to be desired to simplify the preparation processes. Here, poly(vinylidene fluoride) membranes using catechol and polyethyleneimine as the additives were fabricated by non-solvent phase inversion on the non-woven fabric. Hydrophilic polycatechol and polyethyleneimine (PCCh-PEI) aggregates migrated on the top side of the fabricated membranes, improving their hydrophilicity. Furthermore, the hydrophobic back surface with irregular nano/micropores and lots of PVDF spherulites was gained after peeling off the supporting fabric. As a result, the as-prepared Janus membranes showed excellent emulsion separation, stability, and durability, which can potentially be used for unidirectional liquid collection with lossless transportation. This work opens a new and facile way for the fabrication of JMs with asymmetric wettability toward the versatile separation of oil/water emulsions.