Thermodynamic Properties of Poly(ethylene glycol)/Water Systems. 1. A Polymer Sample with a Narrow Molar Mass Distribution

Abstract

Liquid−liquid demixing experiments of a poly(ethylene glycol)/water system have been performed. The polymer is characterized by a nominal molar mass of 6000 g mol-1 and a narrow molar mass distribution. The cloud-point curve of the system and a large number of phase volume ratios at different polymer concentrations and temperatures have been measured. With these results the critical coordinates and the shadow curve of the system have been determined using the volume conservation equation. Generally, the system behaves like a binary one. The miscibility gap is well described using the scaling theory up to temperatures of about 12 K above the lower critical point. The cloud-point and the shadow curve of the system have been computed using the Flory−Huggins theory. For the first time thermodynamic parameters have been used that are calculated directly from the concentrations of coexisting phases obtained by evaluation of phase volume ratio measurements. The examined forms of the interaction function g of the...