A General Approach to Controlling the Surface Composition of Poly(ethylene oxide)-Based Block Copolymers for Antifouling Coatings

Dimitriou, M.D.; Zhou, Z.L.; Yoo, H.S.; Killops, K.L.; Finlay, J.A.; Cone, G.; Sundaram, H.S.; Lynd, N.A.; Barteau, K.P.; Campos, L.M.; Fischer, D.A.; Callow, M.E.; Callow, J.A.; Ober, C.K.; Hawker, C.J.; Kramer, E.J.
Langmuir,
2011
27, 13762-13772.

To control the surface properties of a polystyrene-block-poly(ethylene oxide) diblock copolymer, perfluorinated chemical moieties were specifically incorporated into the block copolymer backbone. A polystyrene-block-poly[(ethylene oxide)-stat-(allyl glycidyl ether)] [PS-b-P(EO-stat-AGE)] statistical diblock terpolymer was synthesized with varying incorporations of allyl glycidyl ether (AGE) in the poly(ethylene oxide) block from 0 to 17 mol %. The pendant alkenes of the AGE repeat units were subsequently functionalized by thiol–ene chemistry with 1H,1H,2H,2H-perfluorooctanethiol, yielding fluorocarbon-functionalized AGE (fAGE) repeat units. 1H NMR spectroscopy and size-exclusion chromatography indicated well-defined structures with complete functionalization of the pendant alkenes. The surfaces of the polymer films were characterized after spray coating by X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption fine structure spectroscopy (NEXAFS), showing that the P(EO-stat-fAGE) block starts to compete with polystyrene to populate the surface after only 1 mol % incorporation of fAGE. Increasing the incorporation of fAGE led to an increased amount of perfluorocarbons on the surface and a decrease in the concentration of PS. At a fAGE incorporation of 8 mol %, PS was not detected at the surface, as measured by NEXAFS spectroscopy. Water contact angles measured by the captive-air-bubble technique showed the underwater surfaces to be dynamic, with advancing and receding contact angles varying by >20°. Protein adsorption studies demonstrated that the fluorinated surfaces effectively prevent nonspecific binding of proteins relative to an unmodified PS-b-PEO diblock copolymer. In biological systems, settlement of spores of the green macroalga Ulva was significantly lower for the fAGE-incorporated polymers compared to the unmodified diblock and a polydimethylsiloxane elastomer standard. Furthermore, the attachment strength of sporelings (young plants) of Ulva was also reduced for the fAGE-containing polymers, affirming their potential as fouling-release coatings.