Designing anti(-bio)fouling membranes with synergistic grafting of quaternized and zwitterionic polymers through surface initiated atom transfer radical polymerization

Abstract

Membrane-based filtration technologies have significant potential to address the global problem of freshwater scarcity. However, fouling, caused by nonspecific adsorption of foulants and microbiological growth during filtration, remains a considerable concern. To address this, a rational surface design method comprising bifunctional coating with both defensive and attacking techniques has been devised, which can successfully decrease fouling and biofouling. To generate a bifunctional membrane, a single-step surface-initiated atom-transfer radical polymerization (SI-ATRP) of monomers with zwitterionic and quaternized imidazolium moieties was done on a polydopamine (PDA) primed polyvinylidene fluoride (PVDF) membrane. The PDA layer’s catechol functionalities provided abundant anchoring sites, allowing the grafting of a dense polymer layer on the membrane. The addition of active zwitterionic and quaternized imidazolium moieties in the grafted polymer chains resulted in very low fouling and microbiological species death. Extensive antifouling studies revealed that the functionalized membranes have excellent flux recovery (>93%), low irreversible fouling (<8.5%), and long-term filtration stability. This surface functionalization strategy based on a bifunctional unit represents a significant advancement in fouling mitigation by minimizing membrane-foulant interactions and killing adhered bacteria, with the potential to significantly broaden the range of membrane-based filtration applications and contribute to more efficient and sustainable water purification processes.