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

Sun, Fang; Mao, G.; Grainger, David W.; Castner, David G.

doi:10.1016/0040-6090(94)90511-8

Cited by 14 publications

(7 citation statements)

References 18 publications

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“…Infrared Spectroscopy. Comparisons of vibrational FTIR spectra acquired from these same ultrathin polymer films at grazing incidence vs bulk coated polymer films also support film organization through differences regarding both vibrational peak position and relative intensity. ,26e Figure presents the FTIR spectral region with various C−F-active IR bands for a perfluoroalkyl-grafted polysiloxane monolayer on gold containing 74% grafted perfluoroalkyl chains. The transmission spectra of the bulk perfluoroalkyl-grafted polysiloxane film (Figure B) is nearly identical to that calculated for a randomly oriented perfluoroalkyl system 26d.…”

Section: Resultsmentioning

confidence: 71%

Spontaneous Polymer Thin Film Assembly and Organization Using Mutually Immiscible Side Chains

et al. 1996

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Polymer ultrathin film self-assembly and organization on solid substrates has been directed using grafted siloxane copolymers bearing mutually immiscible alkyl and perfluoroalkyl side chains. Polysiloxanes grafted with both alkyl disulfide and perfluoroalkyl side chains have been synthesized and characterized. These terpolymer systems assemble spontaneously on gold surfaces, forming bound polymeric monolayers organized by intramolecular phase separation. Interfacially bound polymer monolayer fabrication is driven by multipoint alkyl disulfide side chain chemisorption to gold surfaces from dilute organic solution. Immiscible perfluoroalkyl side chains of low interfacial energy enrich the ambient-exposed outer regions of these monolayers, yielding a novel bound polymer monolayer with an anisotropic, layered structure and perfluorinated surface properties. Ellipsometry indicates that these polymer films have thicknesses ranging from 22 to 32 Å, depending on solution conditions and chemistry. Angular-dependent X-ray photoelectron spectroscopy has provided a depth profile of the bound polymer films, detailing the anisotropic composition resulting from perfluoroalkyl surface enrichment. Static secondary ion mass spectrometry measurements support the enrichment of perfluoroalkyl groups in the outer atomic levels of these films. Cyclic voltammetry using the redox probes Fe(CN) 6 3-and methylviologen with film-coated gold electrodes evaluated film-attenuated electron transfer. Time-of-flight secondary ion mass spectrometry has been used to image micropatterned polymer surfaces lithographed at high resolution both before and after organic monolayer assembly. Qualitative and quantitative information on film spatial organization and surface chemistry distribution on microstructures was obtained.

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Section: Resultsmentioning

confidence: 71%

Spontaneous Polymer Thin Film Assembly and Organization Using Mutually Immiscible Side Chains

et al. 1996

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“…It may be, in part, as a result of the influence of a nonuniform distribution of the analytes ( i.e. the fluorine is all located “on top” of the monlayer, giving rise to the shortest possible path for the ejected electrons), or as a result of adventitious incorporation of fluorine-containing impurities into the monolayers. These possibilities were probed in the following studies.…”

Section: Resultsmentioning

confidence: 99%

Nucleophilic Displacements in Mixed Self-Assembled Monolayers

et al. 1996

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Synthetic elaboration of self-assembled monolayers (SAMs) provides a powerful method for the preparation of smooth, ordered surfaces with carefully controlled functionality. Chemically rugged siloxane-based SAMs have been employed as a foundation for the preparation of a variety of functionalized surfaces. Nucleophilic displacements are described between halide-terminated SAMs and anionic nucleophiles (e.g. azide, thiocyanate, thiolate). Problems were encountered due to the steric congestion surrounding the terminal bromomethylene carbon. The concept of trajectory control is applied to these displacement reactions. In addition, reactions between ester-terminated SAMs and neutral nucleophiles (e.g. amines, hydrazine, hydroxylamine) are described. Evidence is presented suggesting that a modest amount of cross-linking (i.e. imide formation) takes place in the amidation reactions, while reaction stoichiometry indicates that cross-linking is virtually complete for the bifunctional nucleophiles. These synthetic elaborations were also carried out on mixed monolayers to create functionalized SAMs with systematically varied loading densities. Linear correlation (or lack thereof) of elemental composition to predicted functional composition is used to provide an estimation of reaction efficiency.

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“…Inset: M-C6-PMMPS monolayer modified gold electrode with (solid line) and without (dashed line) secondary exposure to fluorothione. (1) M-C6-PMMPS; (2) M-F6-PMMPS; (3) M-PEO-PMMPS; (4) M-PMMPS100.…”

Section: Resultsmentioning

confidence: 99%

Adsorption of Ultrathin Films of Sulfur-Containing Siloxane Oligomers on Gold Surfaces and Their In situ Modification

Sun¹,

Grainger²,

Castner³

et al. 1994

Macromolecules

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Commercially available poly[methyl(mercaptopropyl)siloxane] oligomers have been chemisorbed to gold surfaces from organic solution via gold-alkanes thiolate bonds. Bound films of monolayer thickness (15-20 A) are shown to form spontaneously and are compositionally and structurally isotropic, regardless of solution concentration. X-ray photoelectron spectroscopy yields evidence for two distinct sulfur species in these films: one consistent with gold-thiolate bonds and one representing free, unbonded thiol. A high content of unbonded thiol has been used to modify these organic films in situ using photochemistry. Subsequent exposure of the assemblies to monomeric organothiols does not change film properties. We demonstrate that these siloxane oligomers can be photochemically modified in hulk and assembled on surfaces or, alternatively, that the siloxanes can be chemisorbed as films and subsequently modified in situ to present various functional surfaces. Photochemical derivatizations included alkyl, perfluoor, and polyether chains. Cyclic voltammetry exhibited various redox blocking capabilities for FelCN^3probes depending on film preparation conditions and chemistry. Chemical derivatization disrupted film structure and redox blocking ability, in addition to oxidizing unbound thiol groups. Both pure and photoderivatized siloxane films were perturbed by high-temperature (>100 °C) exposure to solution environments.

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

Cited by 14 publications

References 18 publications

Spontaneous Polymer Thin Film Assembly and Organization Using Mutually Immiscible Side Chains

Spontaneous Polymer Thin Film Assembly and Organization Using Mutually Immiscible Side Chains

Nucleophilic Displacements in Mixed Self-Assembled Monolayers

Adsorption of Ultrathin Films of Sulfur-Containing Siloxane Oligomers on Gold Surfaces and Their In situ Modification

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