Study of the morphology of poly(butylene succinate)/poly(ethylene oxide) blends using hot-stage atomic force microscopy

Blends of poly(butylene succinate) (PBS) and poly(ethylene oxide) (PEO) were cast into films, melted, and crystallized. A number of PBS/PEO blend compositions, ranging from 85/15 to 20/80 were used. The PBS, with a higher melting point, always crystallizes first, providing a scaffold on which the PEO would crystallize. AFM phase and height images were made at room temperature and at higher temperatures, as the PEO melted, allowing one to determine the morphology and location of the PEO. It was found that at low PEO concentrations (below 15 w/o) the PEO resides preferentially between PBS lamellae. This interlamellar PEO does not crystallize, except under extreme undercooling. At higher concentrations, larger amorphous domains exist within the PBS crystalline scaffold and PEO can crystallize in these domains. Two unexpected phenomena are observed: (1) the reversible exuding of PEO from interlamellar spaces to the surface for crystallization and (2) an unusual orientation of PEO lamellae within amorphous domains in the PBS scaffold.