Synergistic solubility behaviour of a polyoxyalkylene block co-polymer and its precipitation from liquid CO2-expanded ethanol as solid microparticles

The solubility behaviour of a polyoxyalkylene block co-polymer surfactant, known as poloxamer F-127, in liquid ethanol/CO2 solvent mixtures at P = 10 MPa and T = 298 K, has been determined. Such a polymer presents a solubility in ethanol/CO2 mixtures that is one or two orders of magnitude larger than in both pure liquids. This synergistic behaviour of ethanol and liquid CO2 to solubilize the poloxamer F-127 has permitted the obtaining of solid particles of the poloxamer suspended in ethanol by depressurising its solutions in liquid ethanol/CO2 mixtures, since the polymer is almost insoluble in the resulting ethanol. This precipitation procedure yields microparticulate solids of the poloxamer with mean particle sizes between 1 and 20 μm. The effects of various operational parameters, like the initial polymer concentration and the CO2 content in the solution, on the resulting mean particle sizes and particle size distribution has been also studied.