Blood compatibility of hydrophilic polyurethane and hydrophobic polystyrene IPNs

Abstract

To investigate the effect of the hydrophilic and hydrophobic domain structure on the blood compatibility, 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 based on polyethylene glycol (PEG), a highly hydrophilic oligomer, and hexamethylene diisocyanate (HDI) with trimethylol propane (TMP)/1,4-butanediol (BD) mixture. The hydrophobic PS network was synthesized through free radical polymerization of styrene monomer and divinylbenzene. The PU/PS IPNs at low temperature were prepared by polymerizing PU component first, followed by the photopolymerization of PS component at low temperature. The fractured surfaces of the PU/PS IPNs exhibited phase separated structures with dispersed PS domains in the continuous PU matrix. The domain size ranged from about 0.1 $\mu$m in U70S30 (70 wt\% PU) to about 0.7 $\mu$m in U30S70. The PU/PS IPNs exhibited two transition temperatures, each corresponding to the component polymers due to the phase separated structure. The PU/PS IPN surfaces also had phase separated structure, but the domain size was smaller compared to the bulk structure. The domain size ranged from about 0.07 $\mu$m in U70S30 to about 0.15 $\mu$ m in U30S70. The enrichment of the hydrophilic PU phase in the surface was revealed by SEM, ATR-FTIR, ESCA, and contact angle measurement. In the fractured surfaces of U50S50 IPNs prerared by varying the synthesis temperature, the domain size decreased with decreasing synthesis temperature. The domain size of U50S50 synthesized at $50\,^\circ\!C$ was 0.15 $\mu$m, but it was 0.05 $\mu$m when synthesized at $-20\,^\circ\!C$ due to the reduced rate of phase separation during the synthesis when polymerized at low temperature. Dynamic mechanical data revealed that the PS phase became more continuous when the IPN was synthesized at low tempera...