Fabrication of high-performance forward osmosis membranes via co-solvent-assisted support-free interfacial polymerization

The co-solvent-assisted interfacial polymerization (CAIP) strategy has proven to be an effective method for fabricating high-performance forward osmosis (FO) membranes. However, current research primarily focuses on the role of co-solvents in conventional interfacial polymerization (IP) technology, with relatively limited studies on unconventional IP technologies. This study explores support-free interfacial polymerization (SFIP) by incorporating dimethyl sulfoxide (DMSO) as a co-solvent. The impact of DMSO on polyamide (PA) structure and membrane performance is systematically investigated throughout the SFIP process. At a DMSO concentration of 1.5 w/v%, SFIP-D1.5 membrane exhibited a high water flux of 29 LMH without a significant increase in reverse salt flux. This phenomenon can be attributed to the dual role of DMSO in promoting monomer diffusion and inducing swelling of the SFIP-PA film. Furthermore, the SFIP-D1.5 membrane exhibited stable performance over 24 h operation and maintained comparable anti-fouling properties during multi-cycle fouling tests. This study reveals the distinct behavior of DMSO in the SFIP process compared to conventional IP, and demonstrates the potential of the CAIP strategy within unconventional IP techniques. This provides a promising approach to enhance both the selectivity and permeability of TFC FO membranes fabricated using strong solvents as co-solvents.