Integration of a Hydrophilic Hyperbranched Polymer and a Quaternary Ammonium Compound to Mitigate Membrane Biofouling

Membrane biofouling, adhesion of microorganisms on the surface and the subsequent formation of a biofilm, remains a persistent and inevitable issue, which results in a dramatic reduction of permeability and lifespan. Constructing a membrane with active bacteria-killing and passive anti-adhesion properties is still a challenge to mitigate membrane biofouling. Herein, an active–passive anti-biofouling membrane was originally fabricated by integration of hydrophilic hyperbranched poly­(N-acryloylmorpholine) (HPA) and the dimethylaminoethyl acrylate–dodecylammonium bromide (DD) quaternary ammonium compound. Inspired by modern dopamine biomimetic adhesion chemistry, thiolated HPA was first immobilized on the polydopamine (PD)-modified poly­(vinylidene fluoride) membrane surface through Michael addition, followed by conjugation of DD via a thiol–ene click reaction. The membrane surface changes of the chemical structure, hydrophilicity, and zeta potential proved that bacteria-killing DD and the anti-adhesion HPA layer were successively conjugated. The initial contact angle of the M-PD/HPA/DD membrane was reduced from 120.5° for the pure membrane to 52.3°. Furthermore, the water flux of the M-PD/HPA/DD membrane increased from 318.9 L m^–2 h^–1 (0.02 MPa) for the pure membrane to 854.4 L m^–2 h^–1. In addition, the M-PD/HPA/DD membrane exhibited excellent active bacteria-killing property with inhibition rates of ∼90% for Escherichia coli and ∼95% for Staphylococcus aureus, respectively. Meanwhile, in the filtration of artificial bacteria wastewater, the M-PD/HPA/DD membrane showed a higher water flux recovery rate of 86.9% than 43.3% for the pure membrane, indicating an excellent anti-biofouling property. Therefore, this molecular-level design approach for the modification of the membrane surface could significantly enhance permeability and mitigate membrane biofouling, which provides a promising dimension for the preparation of the anti-biofouling membrane.