Improved permeability and antifouling performance of Tröger's base polymer-based ultrafiltration membrane via zwitterionization

Tröger's base polymer (TB) has been proved to be applicable to prepare ultrafiltration (UF) membrane and the antifouling property could be improved by hydrophilic modification of TB polymer via a two-step ring-opening reaction transforming the tertiary amine into water-affinitive secondary amine. To improve the permeability and antifouling performance of TB-based UF membrane, a zwitterion-modified Tröger's base polymer (ZTB) was synthesized via one-step reaction and simply blended into the TB membrane matrix. The chemical structure of ZTB was characterized by 1 H NMR and X-ray photoelectron spectroscopy (XPS). The TB/ZTB blend polymers and membrane showed higher hydrophilicity than the pristine TB polymer and membrane. The pore structure can be adjusted via ZTB blending content by affecting the cloud point of casting solution and membrane formation process during non-solvent induced phase separation. The total porosity and average surface pore size of UF membrane were increased by blending ZTB. The permeability and retention factor for BSA of UF membrane were simultaneously enhanced. The static BSA adsorption of UF membrane was reduced from 90.6 μg/cm 2 of the pristine TB membrane to 46.8 μg/cm 2 of TB/ZTB-1.0 membrane. The higher flux recovery ratio of TB/ZTB blend membrane than pristine TB membrane after three fouling-cleaning cycles further demonstrated the enhanced antifouling ability of the TB/ZTB blend membrane. Therefore, the zwitterionization of TB polymer is a feasible method for the permeability and antifouling property enhancement of TB-based UF membrane.