LAUSR

A facile modification method of the aromatic polyamide (APA) thin-film composite (TFC) membrane consisted of two steps. First, the amide N–H group of the aromatic polyamides layer reacted with toluene diisocyanate, which not only eliminated some chlorine-sensitive sites but also left behind the unreacted NCO group on the nascent APA-TFC membrane (referred as to N-membrane) surface. Then, chloride N-(3-formyl-4-hydroxybenzyl)-N,N-dimethyl ammonium-terminated polyethylene glycol (QACs-PEG) was used as the multifunctional alcohol to have an addition reaction with the unreacted NCO group and esterification with the residual acyl chloride group on N-membrane surface. PEG chain terminated with quaternary ammonium cation and salicylaldehyde unit (QACs) was anchored on the APA-TFC membrane surface by these two reactions, and the renascent amide N–H group of carbamide also appeared at the same time. The test results of the modified membrane (M-membrane) performances revealed: (1) due to the abundance of the grafted hydrophilic groups (such as PEG chains and QACs), the surface was superhydrophilic. (2) Compared with the hydrolyzed membrane (H-membrane, prepared from the hydrolysis of N-membrane), the water fluxes of M-membranes significantly increased by nearly 40%. (3) The N–H group of the newly formed urethane was used as a sacrificial unit, which can prevent the aromatic polyamide layer from being corroded by 7 × 105 ppm h chlorine attacking at room temperature. (4) During incubation in the living bacterial suspension, adhesion and growth of gram-negative bacteria Escherichia coli and grampositive bacteria Staphylococcus aureus on M-membrane surfaces had been effectively mitigated, which was due to the combination of the steric repulsion of the water-wetting hydration layer and the synergetic contact-killing capabilities of QACs.