ATR−FTIR is used to investigate the hydrogen-bonding properties of urethane/urea polymers with two soft segments, poly(propylene oxide) and polybutadiene. The polymers are prepared by extending a poly(propylene oxide)-based triisocyanate-terminated prepolymer (PU) with poly(butadienediol) (PBDO). The CO and N−H stretching bands in the spectra of the polymers are deconvoluted into five components, which are ascribed to different free and hydrogen-bonded groups. Results gave evidence of hydrogen bonding between hard/hard segments, leading to the formation of aggregates of urethane/urea groups. This aggregation changed upon variation of the proportion of the two soft segments in the membranes. The increase of PBDO content in the membranes leads to an improvement of the mixing of the two soft segments and also the decrease of the urethane/urea aggregation.

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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.

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