A grafted-liquid lubrication strategy to enhance membrane permeability in viscous liquid separation

While membrane technology has shown promising separation applications, efficient separation of viscous organic liquids remains a great challenge as they can readily adhere to and foul membranes, leading to severely declined permeation flux and even failure of the membranes. Herein, a unique grafted-liquid lubrication strategy is introduced for the first time by covalently grafting highly flexible polydimethylsiloxane (PDMS) brushes onto membranes to tackle the above challenge. The PDMS polymer brush featuring extremely low glass transition temperature (Tg: 127 °C) is rotationally dynamic at room temperature and acts as a liquid-like lubrication layer, which can both reduce the foulant adhesion and promote liquid slippage at the membrane-liquid interface. As a result, a remarkably improved permeation flux and superior antifouling ability towards highly viscous organic liquids (i.e., crude oil) are achieved for the PDMS-brush lubricated membrane compared with conventional solid membranes of similar surface structure and wettability. It is believed that the grafted-liquid lubrication strategy will open a promising avenue for developing high-performance membranes dealing with viscous liquids.