Synthesis of Fluorinated Segment Containing Oligomers for Supercritical CO2 Applications

Syntheses of various fluorine-based surfactants, namely fluorinated-segment-containing block co-oligomers, were achieved by the radical polymerization of mainly acrylate-based monomers. These types of surfactants serve as stabilizers for supercritical carbon dioxide (scCO2) media based applications, for which the effective solubilization of materials in the supercritical phase is generally not possible because of solubility problems faced when CO2 is involved. Initially, a difunctional fluorinated initiator was synthesized in two steps. First, 4,4-azobis-4-cyanovaleric acid was chlorinated with SOCl2, and then the product, 4,4-azobis-4-cyanovaleryl chloride, was reacted with a fluorinated alcohol to obtain the initiator for the polymerization reactions. The synthesized triblock co-oligomers consisted of fluorinated side blocks and a hydrocarbon intermediate block. Efficient solubilization of the materials in scCO2 was observed. It was experimentally shown that the solubility efficiency was affected by specific interactions between CO2 and the oligomers, and these were determined by the nature and size of the inner block and by the chain length of the fluorinated side blocks in comparison with the inner block.