This paper presents a thermodynamic study of aqueous solutions of ethylene oxide-propylene oxide statistical copolymers. In a first step, copolymer samples are carefully characterized by elemental analysis, 1H and 13C nuclear magnetic resonance, gel chromatography and light scattering. Secondly, the lower critical solution temperature is studied as a function of copolymer composition and concentration. This phase separation behaviour as well as the temperature dependences of intrinsic viscosity, second virial coefficient, Flory interaction parameter χ and partial specific volume are discussed in the background of different polymer theories.