Characterization of surface properties of plasma‐polymerized fluorinated hydrocarbon layers: Surface stability as a requirement for permanent water repellency

Plasma polymers were deposited on poly (ethylene terephthalate) (PET) substrates using fluorocarbons such as CF 4 , C 2 F 6 , C 3 F 6 , C 4 F 8 , and mixtures thereof with CH 4 . The fluoro‐carbons selected were of saturated structure (CF 4 , C 2 F 6 ), unsaturated structure (C 3 F 6 ), and cyclic structure (C 4 F 8 ). The addition of CH 4 to any of the fluorocarbons caused a deposition of plasma polymers. However, the deposition rate strongly depended on the amount of CH 4 added. A fluorocarbon‐dominated feed, i.e., fluorocarbons with 17 mol % CH 4 , was found to lead to an effective deposition of plasma polymers, whereas a CH 4 ‐rich feed, i.e., fluorocarbons with 67 mol % CH 4 , led to an ineffective polymer deposition. For the same molar composition of fluorocarbon/CH 4 , polymer deposition depended on the fluorocarbon structure. It decreases in the order C 3 F 6 > C 4 F 8 > C 2 F 6 > CF 4 . Elemental analysis showed an atomic ratio F/C of 2.2 and 2.3 for C 3 F 6 and C 4 F 8 plasma polymer powder, respectively, whereas the corresponding values obtained from X‐ray photoelectron spectra (XPS) surface analysis of films showed 1.5 and 1.6, respectively. An explanation could lie in bulk and surface differences of the deposited layers. Contact‐angle measurements revealed that among the monomers employed only C 3 F 6 with 17 mol % CH 4 resulted in a relatively stable, hydrophobic surface.