Phase behaviour of hyperbranched polyesters and polyethers with modified terminal OH groups in supercritical solvents

Abstract

Hyperbranched polyethers and polyesters have been synthesized, and their phase behaviour in carbon dioxide and light hydrocarbons explored as a function of concentration and temperature. The synthesis includes modifications of the terminal OH groups with aliphatic carboxylic acids derivatives, trimethylchlorosilane, and trifluoroacetic acid anhydride. Modified polyesters show good solubility in carbon dioxide, ethane and propane. The comparison with the literature data shows that the silane and fluorinated derivatives of the hyperbranched polyesters are soluble in carbon dioxide to the same extent as the most CO 2-philic polymeric materials synthesized till now. It seems that the nature of the end groups is an important factor that influences phase equilibria of hyperbranched macromolecules in supercritical solvents. However, the nature of the interior of the macromolecule is also significant. The results obtained show that in general hyperbranched polyesters are better soluble in carbon dioxide than hyperbranched polyethers. In light hydrocarbons as solvents the opposite effect is observed.