For the first time, thin-film composite (TFC) forward osmosis (FO) membranes are fabricated via interfacial polymerization on polysufone (PSf) substrates containing different contents of disulfonated poly (arylene ether sulfone) hydrophilic-hydrophobic multiblock copolymer (BPSH100-BPS0), with the purpose to increase the substrate hydrophilicity while maintaining the mechanical strength. It is found that the tensile strength of the substrate only decrease slightly (23.3%) upon addition of as high as 25 wt% of BPSH100-BPSO in the PSf; while the FO performance of the TFC membrane (TFC-25.0) is significantly improved due to the enhanced hydrophilicity and porosity of the substrate. The TFC-25.0 exhibits extremely high pure water flux of 40.5 LMH in the FO mode and 74.4 LMH in the PRO mode when using 2 M NaCl as the draw solution, which are almost one-fold higher than the TFC membrane without addition of BPSH100-BPSO. The potential of using the TFC-25.0 for desalination is also investigated by using a 2 M NaCl draw solution and a model seawater (3.5 wt NaCl) as the feed. The water fluxes of 18.6 and 29.06 LMH are achieved by the TFC-25.0 under FO mode and PRO mode, respectively. To the best of the authors' knowledge, these values are among the highest in currently reported literature for seawater desalination. (C) 2016 Elsevier B.V. All rights reserved.