Polydioxolane in aqueous solutions. 1. Phase diagram

The phase diagram of a polydioxolane sample (M w =50 000) in aqueous solutions was constructed between -100 and +100°C in the whole range of composition. The solubility domain is limited at higher temperature by the demixing curve (lower critical solution temperature (LCST)= 70°C) and at lower temperature by the melting point of a hydrate (containing three water molecules per monomer unit), and this domain does not extend beyond a polymer content of 50% weightwise. The excess mixing volume is found to be negative and to go through a minimum at 45°C. These findings are compared to those of PEG in water