Surface modification of polyimide films via plasma polymerization and deposition of allylpentafluorobenzene

Plasma polymerization of allylpentafluorobenzene (APFB) on the plasma-pretreated polyimide (PI) films was carried out. The fluorinated aromatic groups of the plasma-polymerized APFB (pp-APFB) could be preserved, to a large extent, by controlling the glow discharge parameters. The effect of the glow discharge parameters, including the type of the carrier gas and the input RF power, on the surface composition and chemical structure of the pp-APFB films were studied by X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and time-of-flight secondary ion mass spectrometry. The surface topography of the APFB plasma-polymerized PI (pp-APFB-PI) films was studied by atomic force microscopy. For plasma polymerization carried out at a high RF power and using argon as the carrier gas, an ultra-hydrophobic pp-APFB-PI surface was also obtained. The ultra-hydrophobic surface exhibited advancing/receding water contact angles (θ_A/θ_R) of 174°/135°. The effectiveness of the carrier gas in defluorinating the pp-APFB films followed the order of O₂ > N₂ > H₂ > Ar. Thus, the role of the carrier gas in improving the surface hydrophobicity of the resulting pp-APFB-PI films followed the order of O₂ < N₂ < H₂ < Ar. The adhesion of the pp-APFB layer to the PI substrate was investigated via solvent extraction and the Scotch® tape adhesion test.