The complexation of ultrahigh‐molecular‐weight poly(ethylene oxide) (PEO) with urea in both the solid and molten states was studied by infrared spectroscopy. Information about the temperature dependences of the absorption bands in the 3600–2600 and 1300–600 cm−1 region on heating and cooling was obtained. Some conclusions concerning the interaction between PEO and urea were also made. The formation of a high temperature, metastable molecular complex between PEO and urea, which is susceptible to undercooling, was confirmed spectroscopically. Heating to 85–90°C resulted in a molecular complex stable at room temperature.© 1994 John Wiley & Sons, Inc.

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X-ray and calorimetric investigations of the structure and transformations on heating of quenched (undercooled) samples of poly(ethy1ene oxide)-urea molecular complexes are discussed. It was established that at room temperature the undercooled melt of the molecular complex contains free urea in a tetragonal crystal modification and a high-temperature poly(ethy1ene oxide)-urea molecular complex whose crystal modification does not coincide with the known hexagonal crystal structure of the molecular complex obtained from solution or by slow cooling from the melt. It was shown that on heating this molecular complex to a temperature between 87,5 and 90 "C, the hexagonal crystal modification, stable at room temperature, is obtained.

Thermoanalytical (thermogravimetry, differential thermogravimetry, and differential thermal analysis) and structural (IR spectroscopy, light microscopy, etc.) methods were employed to estimate the thermal behavior of binary blends of poly(ethylene oxide) (PEO) with copper(II) bromide (CuBr 2 ) of various concentrations under the conditions of a broad temperature interval. Solid residues obtained after heating the blends at different characteristic stages of the thermal destruction were also studied. CuBr 2 introduced in concentrations of 5-10% exhibited a significant thermostabilizing effect on PEO in an air medium, regardless of the mode of the blend preparation. No data about the formation of crystallizing complexes or new compounds prepared from the starting materials on heating the blends were obtained within the concentration range studied (0.1-40% CuBr 2 ). An assumption for the formation of associations between the oxygen atoms of PEO and the metal ion, which obstruct the thermal oxidation processes to a certain degree, were made in order to explain the antioxidative mechanism of action of the inorganic salt.

Low temperature X‐ray analyses were carried out by heating supercooled eutectic systems of water and poly(oxyethylenes) of different molecular weight. Some peculiarities of the eutectic crystallization of the partially or completely glassy eutectic systems during heating depending on the molecular weight of poly(oxyethylene) were established. It was shown that the eutectic components form separate crystal phases. Their crystal modification was determined.