This report describes microphase separated structure, antithrombogenicity, and fatigue behavior of BiomerΩ or segmented polyurethane with various soft segment lengths. The small angle X-ray scattering pattern showed existence of the superstructure with long period, which indicates that the hard and soft segments of segmented polyurethane form microphase separated structure. With an increase of the molecular weight of poly(tetra-methylene glycol) (PTMG) in the soft segment, the long period increased and the glass transition temperature of the soft segment and the extent of hydrogen bonding in urethane carbonyl decreased. Thus, the microphase separated structure is reorganized more distinctly with an increase of the molecular weight of PTMG. The antithrombogenicity of segmented polyurethane was investigated on the basis of the number of adhered platelets and of their morphology on its surface. The antithrombogenicity was improved with an increase of the molecular weight of PTMG. The fatigue strength is closely related to the net hysteresis loss upto the fatigue failure, which is larger for the samples with strongly aggregated hard segment or with low molecular weight PTMG. During cyclic fatigue, the mixing of hard and soft segment phases proceeds to some extent.
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