Self-transformable and blood compatible devices of sulfonated poly(ethylene glycol) acrylate diblock copolymer (PEG-SO₃A/OA) with hydrophilic and hydrophobic block entrapped to polysulfone membrane surface were investigated in terms of the degree of hydrophilicity. The asymmetric membrane was formed by phase inversion process, and the induced hydrophilicity by reorientation of diblock copolymer at interface was verified with contact angle measurement, electron spectroscopy for chemical analysis (ESCA) depth profiling with ion sputtering and platelet adhesion test. Molecular dynamics (MD) simulations for the interface of hydration layer were also performed with various hydrophilic copolymer densities to gain optimum interfacial structure information. The dependency of water clustering behavior around diblock copolymers as a hydrophilicity parameter was described in terms of atom-atom radial distribution function (RDF). The results showed that the diblock copolymer entrapped surfaces demonstrated less platelet adhesion than control or copolymers having no hydrophobic blocks. In addition, oxygen composition significantly began to decrease deeper into the membrane, indicating the reorientation of diblock chains. Copolymer entrapped surfaces significantly induced the degree of water clustering, and the resulting equilibrium rearrangement of interfacial structures was distinctly dependent upon the density of copolymer. Taken together, the results show that the novel concept of in situ self-transformable surface modification strategy was successfully developed for biocompatible ultrathin biomedical membrane device.