Novel mussel-inspired zwitterionic hydrophilic polymer to boost membrane water-treatment performance

Abstract

Although the polyvinylidene fluoride (PVDF) membranes have been widely used for commercial water treatment, the fouling problem adversely affects the membrane deploying longevity, which can be alleviated by the facile surface segregation technology. However, the long-term stability of surface segregation modifiers (SSMs) in membrane is still a challenging issue because the inherent hydrophilicity makes SSMs to slowly dissolve in water. To improve the long-term stability of SSMs and boost the PVDF membrane performance for water treatment, a versatile catechol containing poly (ethylene glycol) modifier with zwitterionic characteristics (SZ-PEG) was synthesized and blended with PVDF to construct PVDF/SZ-PEG membranes with excellent fouling-resistance via surface segregation during non-solvent induced phase separation (NIPS). The incorporation of SZ-PEG endows the membrane with a high porosity through the reduced thermodynamic stability of casting solutions, enhancing the pure water flux of novel SSM modified membrane by 423% compared to the pristine PVDF membrane. Interestingly, the hydrophilic catechol groups in the SZ-PEG polymer accumulate on the membrane surface, resulting in both a high flux recovery ratio (FRR) of ∼96.9% and a good bovine serum albumin (BSA) rejection rate of ∼93.8%. The long-term stability of SZ-PEG polymers in the PVDF/SZ-PEG membrane is proven for 30 day incubation. The interesting findings may offer new insight into surface manipulation of PVDF/SZ-PEG membranes which is particularly effective in tuning the surface characteristics for drug delivery because of their excellent biocompatibility.