To investigate the effect of the hydrophilic and hydrophobic domain structure on the blood compatility, a series of interpenetrating polymer networks (IPNs) composed of hydrophilic polyurethane (PU) and hydrophobic polystyrene (PS) were prepared. The hydrophilic PU network was synthesized by reacting the isocyanate-terminated PU prepolymer with trimethylol propane (TMP)/1,4-butanediol (BD) mixture. The hydrophobic PS network was synthesized through free radical polymerizaion of styrene monomer and divinylbenzene. The PU/PS IPNs at low temperature were prepared by changing the crosslink density of each network and varying the hydrophilicity of PU component.
The fractured surfaces of the PU/PS IPNs exhibited phase separated structures with dispersed PS domains in the continuous PU matrix. The domain size and the swelling ratio in water decreased with decreasing the hydrophilicity of PU component and increasing the crosslink density of each network. The PU/PS IPNs exhibited two transition temperatures, each corresponding to the component polymers due to the phase separated structure. The PU/PS IPNs surfaces also had phase separated structure, but the domain size was smaller compared to the bulk structure. As the crosslink density was increased and the hydrophilicity of PU component was decreased, contact angle data indicated that the PU/PS IPN surfaces became hydrophobic due to the increase of the number of the hydrophobic PS domains and the phase continuity. The enrichment of the hydrophilic PU phase in the surface was revealed by SEM, ESCA and contact angle measurement.
In the in vitro platelet adhesion test, As the crosslink density was increased and the hydrophilicity of PU component was decreased, the IPN surfaces with phase separated structure significantly suppressed the adhesion and activation of platelets.
