Morphology of Elastic and Plastic Poly(Urethane-Imide) Films Observed with TEM and FE-SEM

Direct observation of the morphology of poly(urethane-imide) films, prepared by the reaction of a polyurethane prepolymer and poly(amide acid) as a precursor of polyimide, was performed using transmission electron microscopy (TEM) and field emission scanning electron microscopy (FE-SEM). The poly(urethane-imide) films were plastic or elastic depending on the ratio of the two components. In the plastic films, TEM and FE-SEM analyses clearly showed the presence of urethane-rich domains in the imide-rich continuous phase. Under the higher magnification of TEM, a lamella structure was clearly observed inside the urethane-rich domains. The size and the number of the urethane-rich domains varied with the chemical structure and the ratio of the two components. It was confirmed that the size of the urethane-rich domains in the poly(urethane-imide) films observed with TEM and FE-SEM was almost the same as that of the pores in the porous polyimide films obtained by pyrolyzing the poly(urethane-imide) films at 300–400 °C. In the elastic films, imide-rich domains were clearly seen in the urethane-rich continuous phase by the FESEM observation.