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 (Tgh) 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.