Melting of water/poly(ethylene oxide) systems

Abstract

The transition temperatures of poly(ethylene oxide) (PEO)/water systems were studied over the temperature range from −90 to 110°C by differential scanning calorimetry. The composition of the systems and the average molecular weight of the PEO were varied over a wide range. The systems under study tend to supercool and become partially or completely glassy depending on the cooling rate, composition, and PEO molecular weight. The glassy phases crystallize on being heated above their glass transition temperature. Systems containing about 60 wt % of PEO are most readily super cooled without crystallization. The dependence of melting temperatures and enthalpies on composition was studied and their isobar phase diagrams were drawn. They show that at a definite polymer content (about 50 wt %), which is molecular weight dependent, the systems behave as binary eutectic mixtures. The results confirm the idea that PEO forms quite stable molecular complexes with water.