Morphology of poly(ethylene oxide)/poly(vinyl acetate) blends

The morphology of poly(ethylene oxide)/poly(vinyl acetate) (PEO/PVAc) blends was examined using small angle X-ray scattering (SAXS) and optical microscopy. The morphological and structural parameters of the blends are dependent on both composition and crystallization conditions. Optical microscopy revealed that blend samples prepared by solution casting crystallized with volume-filling crystals up to a composition of 30/70 wt% PEO/PVAc; at higher PVAc content there was no evidence of crystallization in the temperature range studied. Pure PEO always crystallized with a spherulite-hedrite morphology. The formation of spherulites was relatively favoured at lower crystallization temperatures and by addition of PVAc to PEO. Small angle X-ray intensity profiles were analyzed using a recently developed methodology and it was found that, for a given crystallization temperature, the amorphous and interphase thicknesses increased with increasing PVAc content but that the average crystalline thickness was independent of composition. The morphological and structural properties of the PEO/PVAc blends were attributed to the presence of non-crystallizable material in both the interlamellar and interfibrillar regions.