Click preparation and mechanism on amphiphilic oleophobic/hydrophilic behavior of fluorinated diblock copolymers

In this article, amphiphilic fluorinated diblock copolymers of poly(perfluorohexylethyl acrylate)-block-allylpolyethyleneglycol (PF(6)A-b-APEG(1200)) are synthesized by reversible addition-fragmentation transfer (RAFT) polymerization and sequential thiol-ene click reaction. The molecular structure is characterized by H-1 nuclear magnetic resonance (H-1 NMR) spectra and Fourier transform infrared (FTIR) spectra. Morphology and particle size of resultant copolymer micelles in aqueous solution are analyzed by transmission electron microscope (TEM) and dynamic light scattering (DLS). The wettability and relative element contents of PF(6)A-b-APEG(1200) coatings are investigated with contact angle (CA) and X-ray photoelectron spectroscopy (XPS). When PF(6)A-b-APEG(1200) coating is stimulated by water, the fluorine content at the top fluoropolymer-air interface decreases and the water contact angle of the surface decreases over time, showing the hydrophilicity. While stimulated by n-hexadecane, the fluorine content of the film surface increases, showing the oleophobicity with a stable apparent oil contact angle of 72 +/- 1 degrees. According to the detailed analysis of XPS results, the stimuli-responsive behavior of the amphiphilic polymers can be ascribed to the migration and rearrangement of the two blocks in PF(6)A-b-APEG(1200), which might probably be one of the universally accepted oleophobic/hydrophilic mechanisms.