Morphology study of sulfonated poly(ether ether ketone ketone)s (SPEEKK) membranes: The relationship between morphology and transport properties of SPEEKK membranes

The morphological changes of sulfonated poly(ether ether ketone ketone) (SPEEKK) membranes with different sulfonated degrees (Ds) were investigated by small angle X-ray scattering (SAXS), atom force microscopy (AFM) and transmission electron microscope (TEM). The small angle scattering maximum shifts to little vectors with sulfonated degree increasing. Porod analysis for SPEEKK and Guinier analysis for silver exchanged SPEEKK (SPEEKK-Ag) were carried out to study the microstructures of SPEEKK membranes. All the results showed that: more clearly phase-separated structures will be formed with the increasing of Ds of SPEEKK membranes. The membranes with high Ds will provide much larger and more continuous transport channels for protons. The properties changes that derived from the structures’ difference were discussed in detail. The relationship between the properties and microstructures of SPEEKK membranes was established. The study will provide more instructive information on the molecular design of excellent proton exchange membranes.