Films Containing Reactive Mixtures of Perfluoroalkylethyl Methacrylate Copolymers and Fluorinated Isocyanates:  Synthesis and Surface Properties

The fluorotelomer alcohol F(CF2) n (CH2)2OH (n ≈ 7.8), 2, contains a terminal hydroxyl group that reacts with the isocyanate group of a polyisocyanate cross-linking agent based on the isocyanurate trimer of hexamethylene diisocyanate, 1. The resulting fluorinated isocyanate, 3, contains a urethane linkage and a pendant perfluoroalkyl group. The modified isocyanate, 3, was used to prepare films containing acrylic copolymers with cross-linkable hydroxyl groups. Films were prepared using several varieties of acrylic copolymers with and without the incorporation of small amounts of fluorinated monomers. With regards to surface energy reduction, the initial film properties were excellent. For example, reactive mixtures of 3 with hydrocarbon hydroxyl-containing acrylic copolymers exhibited surfaces enriched with fluorine. Water and hexadecane advancing contact angles were measured to be ∼86° and ∼40° at ∼ 2.3 × 10-2 mole fraction (∼1900 ppm by weight F) of F(CF2) n (CH2)2O−, respectively. Hexadecane contact angles on films of copolymer/isocyanate mixtures containing no fluorine were zero. Mixtures of 3 with fluorinated acrylic copolymers gave surfaces that were enriched with fluorine. The source depended on the surface activities of the respective components. Using mixtures of 3 with the various acrylic copolymers, a variety of surfaces can be constructed. The prepared films were examined by contact angle measurements, electron spectroscopy for chemical analysis and dynamic secondary ion mass spectroscopic depth profiling.