Study of the miscibility and crystallization behavior of poly(ethylene oxide)/poly(vinyl alcohol) blends

The miscibility and crystallization behavior of poly(ethylene oxide)/poly(vinyl alcohol) (PEO/PVA) blends were investigated by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and polarizing optical microscopy. Because the glass-transition temperature of PVA was near the melting point of PEO crystalline, an uncommon DSC procedure was used to determine the glass-transition temperature of the PVA-rich phase. From the DSC and DMA results, two glass-transition temperatures, which corresponded to the PEO-rich phase and the PVA-rich phase, were observed. It was an important criterion to indicate that a blend was immiscible. It was also found that the preparation method of samples influenced the morphology and crystallization behaviors of PEO/PVA blends. The domain size of the disperse phase (PVA-rich) for the solution-cast blends was much larger than that for the coprecipitated blends. The crystallinity, spherulitic morphology, and isothermal crystallization behavior of PEO in the solution-cast blends were similar to those of the neat PEO. On the contrary, these properties in the coprecipitated blends were different from those of the neat PEO. (C) 2004 Wiley Periodicals, Inc.