Eutectic-forming binary system of poly(ethylene oxide) and p-hydroxybenzaldehyde

The binary system consisting of poly(ethylene oxide) (PEO) and p-hydroxybenzaldehyde (PHD) was characterized with the aid of differential scanning calorimetry, polarized optical microscopy, scanning electron microscopy and Fourier-transform infrared spectroscopy. The phase diagram created from thermal analysis data provides clear evidence for the presence of a eutectic at 35.5°C and PHD weight fraction of 42%. Microscopy studies show that, for the mixtures with a PHD weight fraction below 42%, the resulting morphology of the crystallized sample is coarse spherulitic texture. In the case of eutectic composition, the crystallization of the binary melt produces degenerated homogenous spherulites. For the hypoeutectic PEO-PHD mixtures, the PHD crystals become large and thick with decreasing the PEO fraction. Moreover, the infrared measurements indicate that hydrogen bonding in the PEO-PHD binary system has an important effect on the PEO helical conformation. With increase of the amount of PHD component, the PEO helical conformation in the PEO-PHD mixtures changes from the 72 helix to the 103 helix. Further increase of the PHD content leads to the destruction of the PEO helical conformation. © 2003 Society of Chemical Industry.