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Characterization of the Microstructure of Poly(propylene oxide)–Segmented Polyamide and Its Suppression of Platelet Adhesion

The relationship between microphase-separated structures and antithrombogenicities of poly(propylene oxide) (PPO)–segmented polyamides of various polyamide segment lengths was studied. Transmission electron microscopic observation revealed fibrillar lamella structures to be present on the copolymer surfaces. Dynamic mechanical and thermal scanning measurements showed the existence of two mechanical relaxations attributable to micro-Brownian motions of the PPO and polyamide segments, indicating that the PPO and polyamide segments formed distinctly separated microdomain structures. Moreover, wide-angle X-ray diffraction and small-angle X-ray scattering measurements indicated these copolymers to be different in their microstructures with respect to size and distribution of crystalline and amorphous domains even though the crystalline structure was essentially the same as that of nylon 610. The degree of platelet adhesion and aggregation was significantly minimized on the surface of the copolymer, in which the average diameter of the crystalline and amorphous domains were 6.42 nm and 5.18 nm, respectively. This suggests that the size of segmented polyamide microdomains may be a determining factor in antithrombogenicity.