Polymer ultrathin films by self-assembly: bound perfluorinated monolayers and their modification using in situ derivatization strategies

Abstract

Siloxane-based grafted copolymers and terpolymers derivatized with pendant dithioalkyl chains, or with both perfluoroalkyl and dithioalkyl side chains, are shown to assemble spontaneously on gold surfaces, yielding bound, anisotropic, polymer ultrathin films. Polymer monolayer assembly is driven by alkyl chain anchoring to solid surfaces by chemisorption from dilute organic media. Limited miscibility between perfluoroalkyl and alkyl hydrocarbon side chains as well as between the siloxane backbone and each side chain component induces a stratified anisotropic monolayer structure. Angular-dependent XPS data show that the siloxane backbone lies primarily between surface-exposed perfluorinated grafts and hydrocarbon chains tethered underneath at the solid surface. Wetting data indicate the hydrophobic influence of perfluoro surface enrichment. Ellipsometry measurements on these films yields 20-30 Å thicknesses. Reflection FT-IR spectra evidence enhanced alignment of perfluoroalkyl grafts in these films as compared to bulk spectra. Once assembled on solid surfaces, these polymer monolayers can be further derivatized with a number of different molecules, providing a defined, stable, organic foundation for surface modification of various types. © 1994.