Star Polymer Gels with Fluorinated Microgels via Star-Star Coupling and Cross-Linking for Water Purification

Two types of star polymer gels containing perfluorinated microgels were created as purification materials to separate polyfluorinated surfactants (e.g., perfluorooctanoic acid) from water. One macrogel is prepared by the radical coupling of fluorine and/or amine-functionalized microgel star polymers alone, while another is done by the radical cross-linking of the star polymers with poly(ethylene glycol) methyl ether methacrylate. Importantly, the reactive olefin remaining within the microgel cores was directly employed for both coupling and cross-linking reactions. Swelling properties of star polymer gels were effectively controlled by the latter cross-linking technique. Analyzed by small-angle X-ray scattering, a star-star coupling gel typically consists of a three-dimensional network where star polymers are sequentially connected with the microgels at the constant interval of about 20 nm. Owing to the fluorous and acid/base cooperative interaction, star polymer gels carrying fluorine/amine-functionalized microgels efficiently captured polyfluorinated surfactants in water and successfully afforded the removal from water via simple mixing and filtration.