Effect of Fractional Fluorination on the Properties of ATRP Surface-Initiated Poly(hydroxyethyl methacrylate) Films

Abstract

Acylation of a surface-initiated poly(hydroxyethyl methacrylate) (PHEMA) film with a perfluoroalkyl acid chloride (C 7 F 15 COCl) results in a highly blocking film with fluorocarbon side groups that orient at the airfilm interface to produce an ultralow-energy surface. The kinetics of the acylation step was monitored with reflectance-absorption infrared spectroscopy to reveal that the rate of fluorination depends on the chain length and solution concentration of the perfluorinated acid chloride as well as the solvent used. By control of the time of exposure to C 7 F 15 COCl, films with fractional conversion of the hydroxyl groups to fluorinated esters between 0 and 0.8 were produced. Increasing fractional conversion from 0 to ∼0.2 has a dramatic effect on surface wettability and electrochemical barrier properties as a densely packed, oriented fluorocarbon surface region is formed that greatly reduces water and ion transport. Additional fluorination has no effect on wettability but gradually increases film resistance while lowering film capacitance. These results suggest that structuring of fluorocarbon groups at the outermost surface of the film has a major impact on film properties and establish the minimum content of fluorocarbon groups required to achieve the structured interface via this grafting process.

Physicochemical Properties of Surface‐Initiated Polymer Films in the Modification and Processing of Materials

“…[64] Low-energy surfaces are commonly generated by preparing thin films in which relatively non-polar groups such as ±CF 3 or ±CH 3 dominate the surface composition. We have recently used surface-initiated ATRP to grow poly(hydroxyethyl methacrylate) (PHEMA) films on gold that were subsequently modified by acylation with acid chlorides (RCOCl) of hydrocarbon (R = C p H 2p+1 ) [71] or fluorocarbon (R = C m F 2m+1 ; R = C 6 F 5 ) [69,70] composition to produce ester-linked side groups (Scheme 1). The wettability of these films, also shown in Scheme 1 via advancing contact angles of water and hexadecane, depended on the composition and chain length of the side group.…”

Design of complex polymeric architectures and nanostructured materials/hybrids by living radical polymerization of hydroxylated monomers

“…Gold surfaces covered with partially fluorinated P(HEMA) polymers have were reported by Bantz et al 129 In this work, P(HEMA) was grown from Br functionalised gold surfaces via surface initiated ATRP followed by acylation of the P(HEMA) brushes with perfluoroalkyl acid chlorides. The contact time for acylation was carefully controlled in order to obtain various degrees of acylation, which ranged from 0 to 0.8.…”

Formation of surface-grafted polymeric amphiphilic coatings comprising ethylene glycol and fluorinated groups and their response to protein adsorption

“…[21][22][23][24][25] Three different acylchlorides were employed ͑all obtained from Sigma-Aldrich͒: heptafluorobutyryl chloride ͑C 3 F 7 COCl, F3͒, pentadecafluoro-octanoyl chloride ͑C 7 F 15 COCl, F7͒, and pentafluorobenzoyl chloride ͑C 6 F 5 COCl, PFA͒. Substrates with PHEMA brushes were exposed to 80 mM solutions of a given acylchloride with 100 mM pyridine in dichloromethane for 24 h at room temperature to modify PHEMA films with fluorinated side chains ͑see Fig.…”