Hybrid Star-Shaped Block Copolymers for Fabricating Fouling-Resistant Membranes

Abstract

Star-shaped block copolymers (SPs), comprising a hydrophobic cross-linked polystyrene (PS) core with extended hydrophilic polyethylene glycol (PEG) arms, showed high promise as a class of branched amphiphilic coating material, since the coatability and antifouling properties of the SPs could be tailored simply by tuning the core and/or arm compositions. However, the complex reaction sequences required for synthesizing SPs have been an obstacle for scale-up and, therefore, their practical applications. Herein, we have developed an SP architecture from an inorganic silica nanoparticle (SiO2NP) core, significantly simplifying the synthesis and enabling scale-up at much lower costs. The pressure-assisted coatability of three SiSPs with three different PEG lengths (i.e., SiSP1, SiSP2, and SiSP3 with 28, 54, and 129 PEGMA repeating units) on polysulfone ultrafiltration membranes was evaluated by scanning electron microscopy (SEM) and contact angle measurement. The SiSPs with medium PEG arm length (i.e., SiSP2 with 54 PEGMA repeating units) demonstrated superior thin-layer coatability and UV-induced stabilization. The protein solution filtration exhibited very low fouling, ca. 3% flux decline ratio (FDR) and ca. 97% flux recovery ratio (FRR), for UV-SiSP2 coated PSF UF membrane compared to significant fouling for pristine membrane (ca. 41% FDR and ca. 71% FRR). The three times enhancement in oleophobicity of the SiSP2 coated membrane has endowed almost seven times improvement in the permeation flux during oil emulsion filtration and 100% FRR contrary to zero flux recovery for pristine membrane. This study offers insights regarding the cost-efficient and facile synthesis of block copolymer nanoarchitecture SiSPs, which has the potential for water purification, lubrication, emulsification, and biomedical applications.