Enhanced anti–protein fouling of PVDF membrane via hydrophobic–hydrophobic adsorption of styrene–terminated amphiphilic linker

The amphiphilic copolymer polystyrene-maleic anhydride (SMA)-2-hydroxyethyl acrylate (HEA) was synthesized for the first time in this study, and used as a linker to graft zwitterionic sulfobetaine methacrylate (SBMA) in order to enhance the hydrophilicity and anti-adsorption ability of polyvinylidene difluoride (PVDF) membranes. This amphiphile linker is composed of a hydrophobic extremity, i.e., the SMA copolymer, and a hydrophilic extremity, i.e., the HEA. The SMA-HEA linker was first dispersed into the PVDF matrix via the blending method, and the hydrophobic polystyrene of SMA was adsorbed into the PVDF membrane via hydrophobic–hydrophobic interaction. The SBMA was then grafted onto the expanded HEA via free radical polymerization. The functional groups, morphologies, and hydrophilicity of the amphiphile-modified PVDF membranes were analyzed by attenuated total reflection Fourier-transform infrared spectroscopy (ATR-FTIR), field emission scanning electron microscopy (FE-SEM), and water contact angle (WCA) measurements. The PVDF membrane modified with the SMA-HEA amphiphile linker showed significant enhancement in hydrophilicity as the WCA decreased from 135.0° to 45.0°, and the protein adsorption of the modified membrane decreased from 112.5 to 33.3 μg⋅cm−2. Furthermore, dynamic protein separation was performed, and the pure water flux recovery rate reached 100%, indicating good anti-adsorption ability.