Interaction of poly(ethylene oxide) with solvents: 2. Water-poly(ethylene glycol)

Differential scanning calorimetry (d.s.c.) and water vapour pressure measurement have been used to investigate the poly(ethylene glycol) (PEG) interaction with water. There is a clear evidence for the existence of stable crystalline complexes. One complex clearly contains three moles of water per ether group and exists even at a concentration of 1 part by weight of PEG in 17 parts of water. It melts below p°C. The vapour pressure results indicate a lower hydrate, which could be a monohydrate, but the evidence from the d.s.c. analysis for this hydrate is less definitive. The formation and stability of these hydrates as a function of molecular weight is further discussed relative to ΔHfus and ΔSfus values determined from d.s.c. curves.