Fabrication of low-shrinkage hydrophilic zwitterionic coating by radical photopolymerization using branched macromonomer as cross-linker for oil/water emulsion separation

• Polymerization kinetics of linear and branched Poly(HEA) via RDRP in aqueous solution were investigated. • Linear and branched Poly(HEA) coatings were prepared by SI-RDRP to membrane surfaces. • Branched Poly(HEA) brush coating showed more excellent antifouling performance. Fabrication of hydrophilic coatings on membrane surface is one of the best methods to solve membrane fouling caused by oil or other pollutants. Recently, branched macromonomer as cross-linker in polymerization are proved to favor the uniformity and stability of coatings. Herein, we synthesized a branched macromonomer poly(ethylene glycol dimethacrylate) (BP(EGDMA)), which had abundant vinyl groups via catalytic chain transfer polymerization (CCTP), for fabrication of zwitterionic hydrophilic coatings with low volume shrinkage on different surface through photopolymerization. The low molecular weight cross-linkers with different functionality were used as control groups. The results of polymerization on glass plate showed that the hydrophilic coatings cross-linked by BP(EGDMA) was more uniform and stable. The surface chemistry, wettability and permeability of membranes were further investigated. The results showed that coatings which used macromonomer BP(EGDMA) as cross-linker on porous membrane surface was still more uniform than those which used low molecular weight cross-linkers. Meanwhile, the effects of the irradiation time and monomer usage on membrane coatings were explored to choose the best fabrication condition. Under the suitable conditions, the membrane used BP(EGDMA) as cross-linker showed a high oil rejection of >99 % among several oil-in-water emulsion. Moreover, the anti-biofouling experiment revealed that the macromonomer BP(EGDMA) would endow hydrophilic coatings with better fouling resistance by longer irradiation time and larger total monomer usage.