Synthesis and characterization of flat-sheet thin film composite forward osmosis membranes

► Thin film composite forward osmosis (FO) membranes with tailored substrates were synthesized. ► The FO water flux depends on both rejection layer permeability and substrate structure. ► Finger-like pore structure is preferred over spongy-like structure for FO applications. ► The Jv/Js ratio increases with B/A ratio.