Measurements of the phase behaviour of the system dextran/DMSO/CO ₂ at high pressures

This paper deals with the measurements of the phase behaviour at high pressures of the system dextran/dimethylsulphoxide/CO₂, a system that is being used to study the micronisation of biodegradable polymers using the PCA process. The study of the phase behaviour has been performed combining two independent measurement techniques. It will be shown that the variable composition view cell method recently developed [1] is a useful, easy and reliable method that can be applied to study polymer systems. It can be used to determine the amount of CO₂ needed to induce a liquid-liquid phase split in the polymer solution within a 1-2 wt.% error. However, this method was not sensitive enough to predict how the studied system reacts to moderate changes in pressure and temperature. The Cailletet tube method was used to obtain more accurate PT data (isopleths) to complete the information on the phase behaviour of the system. The influence on the PT phase behaviour of the concentration of CO₂, the concentration of dextran as well as the presence of water in the system was studied.