Surface and hemocompatibility studies of bi-soft segment polyurethane membranes.

Cross-linked urethane/urea membranes with two soft segments were prepared by extending a poly(propylene oxide) based tri-isocyanate-terminated prepolymer (PUR) with polybutadiene diol (PBDO). The ratio of prepolymer and polybutadiene diol was varied to yield cross-linked membranes with different compositions, exhibiting different degrees of phase-separation of the PBDO segments in the bulk and of surface enrichment in PUR. In this work, surface energy and hemocompatibility aspects (hemolysis and thrombosis) of the PUR/PBDO membranes were evaluated. The results showed that the membrane surface energy increased with the PBDO content until 25% of PBDO, and decreased thereafter. The introduction of the second, more hydrophobic, soft segment (PBDO) in the PUR membranes turned hemolytic into non-hemolytic membranes and, for a blood-material contact time of 10 minutes, decreased the thrombogenicity significantly. The 10% PBDO membrane was the least thrombogenic and was also non-hemolytic. The hemolysis degree did not vary significantly with the PBDO content while, for blood-material contact times of 10 minutes, the thrombogenicity increased with an increase in PBDO content above 10%. Membrane thrombogenicity varied with the blood-material contact time. For blood contact times of 10 minutes, all membranes tested were less thrombogenic than glass.