PIB-based polyurethanes. IV. the morphology of polyurethanes containing soft co-segments

Abstract

Novel polyurethanes consisting of polyisobutylene (PIB)/poly(tetramethylene oxide) (PTMO) or PIB/poly(hexamethylene carbonate) (PC) soft co-segments in combination with 4,4'-methylene-bis(cyclohexyl isocyanate)/1,6-hexanediol, 1,4-butanediol, or 1,6-hexamethylene diamine hard segments exhibit excellent mechanical properties (upto 31 MPa tensile strength with 700% elongation) together with unprecedented oxidative/hydrolytic stability. A structural model of the morphology of these polyurethanes was developed that reflects this combination of properties. The key new elements of our model are H bridges between the PTMO and PC type soft and urethane hard segments, which compatibilize the soft and hard domains, and the presence of large quantities of chemically resistant PIB soft segments that protect the other oxidatively/hydrolytically vulnerable constituents. A variety of FTIR, DSC, SAXS, AFM, and DMTA experiments strongly support the proposed morphological model.