Phase Behavior of Polyethylene Oxide-Fullerene

Phase transitions (glass, melting, crystallization) are important features of materials. The dispersion of (nano)particles within homopolymers results in complex modifications of their thermal properties. A study focused on two materials with the same composition: polyethylene oxide (PEO) and fullerene (C60) is reported. PEO-C60 nanocomposites (PEO-C60NC) were obtained by dissolving PEO in water, dispersing fullerene in water, homogenizing these dispersions, mixing them, homogenizing the obtained mixture, and removing the water. Because C60 is insoluble in water, a standard nanocomposite (PEO-C60NC) was obtained. Molecular dispersions of C60 in PEO (PEO-C60MD) were obtained by dissolving the polymer in toluene, the fullerenes in toluene, homogenizing each solution, mixing the two solutions, and removing the solvent. With a diameter of about 1.1 nm, fullerene provides a huge surface area that affects the phase transitions of PEO. Thermal features of PEO-C60NC and PEO-C60MD have been measured by Differential Scanning Calorimetry by using the Netzsche instrument. Thermograms were recorded at various heating/cooling rates in the range of 5 to 50 oC/min. The effect of cooling and heating rate as well as the effect of the loading by fullerene on glass, melting, and crystallization of PEO is reported. The differences between PEO-C60NC and PEO-C60MD are analyzed in detail.