Deposition of well-defined fluoropolymer nanospheres on PET substrate by plasma polymerization of heptadecafluorodecyl acrylate and their potential application as a protective layer

Fluoropolymer films consisting of well-defined nanospheres were deposited via pulsed plasma polymerization of 3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-heptadecafluorodecyl acrylate (HDFA) on flexible poly(ethylene terephthalate) (PET) substrates. The morphology of the nanostructured flouropolymer films was studied by field emmision scanning electron microscopy (FESEM) and atomic force microscopy (AFM). The mean diameter (D_m) and standard deviation in diameter (SD) of the fluoropolymer nanospheres, as derived from the surface FESEM images of the films, were about 17 nm and 2 mn, respectively. The formation of highly uniform and well-sructured nanospheres was achieved through the removal of the reactive species and the monomer in-between successive plasma bursts. The interspersed cleaning and monomer-free purging process eliminated the post-plasma polymerization effect (polymerization carried out by the persisting radicals and ions on the nanoparticle surface during the plasma-off period) and allowed a better control of the particle growth. The chemical composition of the nanostructured fluoropolymer films was studied by X-ray photoelectron spectroscopy (XPS). The performance of the nanostructured fluoropolymer film as a barrier against water absorption and its effect on the transparency of the PET substrate on the visible region, upon prolonged exposure to water at an elevated temperature, were also evaluted.