Membrane technology is currently still excluded from separations in more aggressive feeds due to limited chemical robustness. To extent its applicability, a novel thin-film composite (TFC) membrane was synthesized via the homopolymerization of epoxide monomers, resulting in robust poly(epoxyether) top-layers with > 90% rose bengal (MW = 1017 Da) and 70% methyl orange (MW = 327 Da) retention with reasonable water fluxes (> 2 Lm(-2) h(-1) bar(-1)). The superior chemical stability of this novel nanofiltration membrane type was proven via treatments in pH 1 and 500 ppm NaOCl (pH 4) for, respectively, 48 h and 2.5 h, after which an unchanged or even improved membrane performance was observed. Additionally, the synthesis of the thin top-layer occurred via an interfacial initiation of the polymerization (IIP), rather than via state-of-the-art interfacial polymerization (IP). This IIP approach allowed to convert well-known monophasic bulk epoxide polymerization (commonly used in e.g. the automotive and coating industry), into the synthesis of thin, yet cross-linked top-layers.