Morphology copolyurethane

While AB block copolymers are known to phase separate into relatively pure two-phase morphologies, multiple block copolymers such as these block copolyurethanes may not necessarily have such a complete phase separation. 

The surface morphologies of these block copolyurethanes differ from their bulk morphologies (4-6). Because the surface controls the interaction of a vascular implant with blood, the surface structure and its relation to the bulk structure of the same material was determined also. Originally, ESCA was explored to study the surface structure because the depth of penetration was within the first 100 A. The low surface depth of penetration and subtle shifts in binding energies that result in peak splittings of the elemental spectra appeared to make this an attractive method to study the chemical and bonding environments of the elements (40). 

In summary, the surface chemical and morphological structures of block copolyether-urethane-ureas may be determined by ESCA and FTIR coupled with internal reflectance techniques to probe the surface and bulk structures. These ESCA and FTIR data are being used to model the domain-interface structure of these copolyurethanes and their interaction with blood protein. 

To understand the interaction of LiBr with the copolyurethanes and the resulting morphological changes, nonextracted samples of PEUU 700 were studied, because this copolyurethane exhibited the largest variation in water absorption and tensile strength as a function of salt concentration. 

Thus, the addition of LiBr to the copolyurethane casting solution does allow the formation of films having morphologies that cause these hydro-phobic polymers to form hydrogels. 

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