FTIR studies on the compatibility of hard-soft segments for polyurethane-imide copolymers with different soft segments

The polyurethane-imide (PUI) copolymers with different soft segments (polyethylene-co-propylene adipates, polyethylene glycol, or polypropylene-oxide) were studied. FTIR spectroscopy shows the different absorption bands of imide-I groups and reveals the different intermolecular interactions due to hydrogen bonding in these PUI copolymers. FTIR results suggest there is a good compatibility between hard and soft segments in either polyester-PUIs or polyether-PUIs having short soft segments. On the other hand, DSC analysis reveals that the glass transition temperature for hard segments (T_gh) of polyether-PUIs is higher than that of polyester-PUIs, and it increases with the soft segment length in PUIs consisting of the same type soft segments, which further supports the conclusions drawn from the FTIR data.