In this study, we investigate the use of reactable substrates for interfacial polymerization of polyamide membranes. Two reactable group (hydroxyl group) contained substrates were prepared. Using m-phenylenediamine (MPD) and trimesoyl chloride (TMC) as monomers, thin film composite (TFC) membrane formed thereon displayed varying film morphology, chemical composition and separation performance. The substrate participating TFC membrane showed a thicker rejection layer with greater crosslinking density. The latter was caused by the formation of ester bonds in addition to amide bonds. This polyamide/polyester composite rejection layer had greatly enhanced NaCl and Na2SO4 rejection compared to the control membrane prepared on inert substrate. We further proposed a conceptual model that highlighted the important role of amphiphilic copolymers as (1) MPD enrichment loaders, (2) reactive monomers and (3) surfactants in the interfacial polymerization process.