Effect of carboxylate and/or sulphonate ion incorporation on the physical and blood-contacting properties of a polyetherurethane.

Propyl sulphonate and ethyl carboxylate groups were grafted on to the backbone of a polytetramethylene oxide-based polyurethane (PEU). The effects of ion type and ion content on the polymer's bulk, surface, and blood-contacting properties were evaluated. Ion incorporation disrupted the packing of the hard segment but had little effect on the overall microphase separation of the polymers. The mechanical properties of the ionomers were improved relative to the base PEU, although the carboxylate-containing ionomers were weaker than the sulphonate-containing polymers. As expected, the polymer's water absorption and surface polarity increased with increasing ion content. Dynamic and static contact angle analysis indicated that the propyl sulphonate-containing polymers were more polar than the ethyl carboxylate-containing polymers at the same ion content which is attributed to the higher ionic strength of the sulphonate ion. The carboxylate-containing polymers had no statistically significant effect on the polymer's canine ex vivo blood-contacting response. At the same ion content, propyl sulphonate incorporation significantly reduced platelet deposition for very short blood-contacting times. When both ion types were present in the polymer, the propyl sulphonate group appeared to be the primary factor determining the polymer's blood-contacting response. The polymer containing 20 mol% propyl sulphonate groups significantly reduced platelet deposition and activation while also exhibiting enhanced fibrinogen deposition.