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| - Effect of Fractional Fluorination on the Properties of ATRP Surface-InitiatedPoly(hydroxyethyl methacrylate) Films
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| - Acylation of a surface-initiated poly(hydroxyethyl methacrylate) (PHEMA) film with a perfluoroalkyl acidchloride (C7F15COCl) results in a highly blocking film with fluorocarbon side groups that orient at the air−film interface to produce an ultralow-energy surface. The kinetics of the acylation step was monitored withreflectance-absorption infrared spectroscopy to reveal that the rate of fluorination depends on the chain lengthand solution concentration of the perfluorinated acid chloride as well as the solvent used. By control of thetime of exposure to C7F15COCl, films with fractional conversion of the hydroxyl groups to fluorinated estersbetween 0 and 0.8 were produced. Increasing fractional conversion from 0 to ∼0.2 has a dramatic effect onsurface wettability and electrochemical barrier properties as a densely packed, oriented fluorocarbon surfaceregion is formed that greatly reduces water and ion transport. Additional fluorination has no effect on wettabilitybut gradually increases film resistance while lowering film capacitance. These results suggest that structuringof fluorocarbon groups at the outermost surface of the film has a major impact on film properties and establishthe minimum content of fluorocarbon groups required to achieve the structured interface via this graftingprocess.
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