Effect of surface hydrophilicity on ex vivo blood compatibility of segmented polyurethanes

The relationship between surface, bulk and ex vivo blood-contacting properties of segmented polyurethanes with various polyol soft segment was investigated. The polyols used in this study were poly(ethylene oxide), poly(tetramethylene oxide), hydrogenated poly(butadiene), poly(butadiene) and poly(dimethylsiloxane). The hard segment of these segmented polyurethanes was composed of 4,4' diphenylmethane diisocyanate and 1,4 butanediol, present at 50 wt%. An experimental polyurethane, Biostable PUR, which has shown excellent biostability, was used in this study. The segmented polyurethanes based on the hydrophobic polyols such as poly(dimethylsiloxane) and hydrogenated poly(butadiene) showed distinct microphase separation between hard and soft segments. X-ray photoelectron spectroscopy revealed the surface enrichment of the hydrophobic component at the air-solid interface. Dynamic contact angle measurements indicated that the poly(dimethylsiloxane)-based segmented polyurethane possessed a hydrophobic surface in water. The poly(dimethylsiloxane)-based segmented polyurethane had the lowest platelet adhesion among the segmented polyurethanes investigated in this study, whilst the platelet deposition on the poly(ethylene oxide)-based polymer increased with time.