Surface modification of polyurethanes by multicomponent polyaddition reaction
It has been proposed that both good mechanical properties and improved haemocompatibility of segmented polyurethanes (PURs) are caused by the separation of hard and soft segments. The differences between the stoichiometric and surface composition were explained by a higher concentration of soft segments at the surface and it was shown that the surface structure is influenced by its environment. Moreover, the balance of polar (hydrophilic) and non-polar (hydrophobic) sites at the polymer surface may be important for their blood compatibility. It is possible to influence the properties of PURs, including their surface properties, by the choice of starting materials and their composition. Accordingly, the aim of our study was to tailor surface structures with desired properties by a multicomponent polyaddition reaction with selected monomers. From the atomic composition of the measured by ESCA and the calculation of the soft- and hard-segment concentrations the enrichment of hydrophobic polyisobutylene at the polymer surface as well as a quasi-independence of the bulk composition were concluded. The results confirm our morphological model of multicomponent PURs deduced from indirect methods involving molecular dynamics.