Poly(ether-block-sulfonated ester) copolymers. III. Morphology and ionic aggregation in PESE

Sulfonated poly(ether–ester) copolymers (PESE) based on poly(butylene terephthalate-co-butylene 5′-sulfoisophthalate sodium salt) and poly(1,4-oxytetramethylene) were studied. Morphological changes that can occur as a consequence of interactions of the sulfonate groups in PESE were investigated by using differential scattering calorimetry (DSC), wide- and small-angle x-ray scattering, and scanning electron microscope measurements. The x-ray scattering and DSC studies show that the degree of crystallinity decreases with increasing content of ionic groups in the polyester rigid segments. This change is the result of ionic forces caused by incorporation of the ionic units. A morphology of ionic aggregates inside microphase-separated poly(butylene terephthalate) domains is suggested.