Synthesis of Hyperbranched, Hydrophilic Fluorinated Surface Grafts

The synthesis of 60−1000 Å thick films of fluorinated polymers on gold and silica substrates via amidation of layered, hyperbranched poly(acrylic acid) surface-graft films with a fluorinated octylamine is described. These syntheses proceed either by formation and fluoramidation of layers of poly(acrylic acid) or by stepwise formation of layers of a mixture of poly(acrylic acid) and a fluorinated poly(acrylamide) on a carboxylic acid-containing self-assembled monolayer on gold or on aminopropylated silica. Depending on the chemistry used, these grafts can be prepared so that they have fluorinated interiors and either hydrophobic or hydrophilic exteriors. Ellipsometric studies of these grafts on gold show that the thickness of the layers can be controlled on the basis of the number of PAA layers present and that fluorination using a fluorinated octylamine roughly doubled layer thickness. Infrared and X-ray photoelectron spectroscopy studies were used to characterize these surfaces.