The synthetic polymer surface which has a microphase separated structure often shows good blood compatibility, though the reason why was still uncertain. The interaction of platelet with the films of the block copolymer composed of 2-hydroxyethyl methacrylate and styrene was studied by the column beads method in order to clarify the mechanism of the interfacial interaction of blood with a microphase separated structure. The results showed that adhesion and deformation of platelets on the surface of the block copolymers containing 0.347 and 0.608 mole fraction of HEMA were less than those of the PSt, PHEMA and HEMA-St random copolymer. The effect of the microdomains of the block copolymer on the antithrombogenecity was discussed.
