Properties and biological interactions of polyurethane anionomers: effect of sulfonate incorporation.

In order to investigate the factors affecting the interaction of polyurethanes and blood, a series of poly(tetramethylene oxide)-based polyurethane block copolymers was synthesized with systematically varying levels of ion incorporation in the hard segment block. A bimolecular nucleophilic substitution reaction was used to replace up to 20% of the urethane hydrogens with propyl sulfonate groups. Bulk and surface characterization was performed, and a canine ex vivo arteriovenous shunt was used to monitor initial platelet and fibrinogen deposition on these surfaces. The microphase separation and bulk physical properties were found to vary with ionic content. Surface analysis using both in vacuo (ESCA) and water-equilibrated (contact angle) methods indicated that these polymers, and especially the highly sulfonated materials, could rearrange to minimize their interfacial tension, depending on the contacting environment. Platelet deposition onto these materials decreased as the level of sulfonation increased, with the highly sulfonated polymer showing substantially less platelet spreading and activation than previously seen in the same experiment with other polymers.