Interpenetrating polymer networks(IPN's) of hydrophilic polyurethane (PU) and hydrophobic polystyrene(PS) were prepared by simultaneous polymerization method. Hydrophilicity of the material was controlled by varying the PU composition and ionizing the PU network. The size of the hydrophilic and hydrophobic domain was also controlled by varying the synthesis pressure. The degree of hydrophilicity was measured by the swelling ratio in water. The surface free energy and the solid-water interfacial energy were measured by measuring the contact angle.
The effect of the hydrophilic and hydrophobic microdomains of the IPN's on the blood compatibility were studied by platelet adherence test.
The surface morphology of PU/PS IPN's exhibited hydrophilic-hydrophobic microphase-separated structures which have the dispersed PS domains in the continuous PU matrix. The domain size decreased as the synthesis pressure was increased. In the case of the PU and PS homopolymer and the PU/PS IPN containing the zwitterion PU network, significant degree of platelet adhesion and aggregation was observed. However, the platelet adhesion and deformation was suppressed on the surfaces on IPN's of hydrophilic-hydrophobic microphase-separated structure.
