Effect of Acetylation on the Behavior of Hyperbranched Polyglycerols in Supercritical CO2

Processes using CO2 either as a solvent or as a reactant, for example, in catalyzed chemical reactions, are increasing in interest due to their green characteristics. Hyperbranched polyglycerols have the potential to be used as support for catalysts in these processes, allowing for an efficient separation of the products and the reutilization of the catalyst, but this requires them to absorb CO2. Acetylating hydroxylated compounds has shown to be an efficient way to increase their CO2-philicity, and this work aims to understand how acetylation increases the interaction of hyperbranched polyglycerols with different cores with supercritical CO2. This involves the study of their kinetics of expansion in this media (from 10 to 25 MPa and at 35 °C and 45 °C) and, eventually, their solubility when it happens. The expansion of the acetylated polyglycerols reached up to 66% in volume, while that of non-acetylated ones, in general, do not exceed 10%. Acetylation plays an important role in increasing the expansion of these polymers in the presence of CO2 and, therefore, in increasing their CO2-philicity and CO2 absorption, making them potential materials to be used in biphasic (polymer/CO2) reaction systems.