The structure of polyoxyethylene solutions with lower critical temperatures of mixing

Abstract

The phase equilibrium, light scattering and viscosity of solutions of polyoxyethylene (POE) in water have been studied. The molecular weights, second virial coefficients and size and concentration fluctuations of the macromolecules and particles causing light scattering have been calculated. It is shown that for a system with a lower critical temperature of mixing, as for those with an upper critical temperature of mixing, the R″ 90 = ƒ(T) curves contain a sharp peak corresponding to the temperature of phase separation ( T p.s.) of the system. It was found that as T p.s. is approached structure formation occurs in homogeneous solutions of POE, as a result of worsening of the thermodynamic quality of the solvent. This is manifested as a gradual increase in light scattering, in the size of the light-scattering particles and in fluctuations of concentration.