Improved antifouling properties of membranes by simple introduction of zwitterionic copolymers via electrostatic adsorption

In this study, a simple approach was proposed to incorporate zwitterionic copolymers into polymer membranes via electrostatic adsorption to reduce organic fouling and biofouling. Zwitterionic copolymers carrying positive charges were successfully synthesized from [2-(methacryloyloxy) ethyl] dimethyl-(3-sulfopropyl) ammonium hydroxide (SBMA) and [2-(methacryloyloxy) ethyl] trimethylammonium chloride (MTAC) via radical polymerization. Quartz crystal microbalance (QCM) measurements were conducted to identify the optimum copolymer with suitable monomer ratio for surface coating. The copolymer with an SBMA to MTAC ratio of 7:3, and 1000 ppm polymer concentration showed the highest adsorption. A negatively charged membrane was modified with this zwitterionic copolymer by the dip-coating method, which was finished in 1 min. The surface properties and antifouling properties (i.e. anti-organic fouling and anti-biofouling) of the membranes were characterized. Moreover, the modified membrane was stable in various chemical solutions. Results indicated that improved anti-organic fouling and anti-biofouling properties was attributed to improved hydrophilicity and reduced negative charge. The zwitterionic coating layer was stable after treatment with various solutions (e.g., 70% ethanol, 0.01 M sodium dodecyl sulfate (SDS), 0.1 M sodium chloride (NaCl), and a pH11 aqueous solution) for 6 h. This study provides a simple, stable method of modifying negatively charged membrane to improve antifouling properties, which is of great importance in biomedicine.