Perfluorinated polymer surfaces comprising SF5-terminated long-chain perfluoroacrylate

A new perfluorinated acrylate monomer containing the SF₅(CF₂)₆-perfluorinated side chain was synthesized and polymerized into films. Bulk monomer characterization is consistent with the molecular structure based on FTIR, mass spectrometry and NMR analyses. The surface properties of polymer coatings were studied with aqueous wetting (contact angle) and X-ray photoelectron spectroscopy (XPS) methods. The surface composition is shown to be highly enriched in the terminal side chain SF₅-chemistry and exhibits properties consistent with a highly apolar, non-wetting perfluorinated polymer surface. Depth-dependent XPS studies using angular-resolved methods (ADXPS) confirmed a non-stoichiometric enrichment of sulfur and fluorine at the film ambient interface, consistent with a surface presence of the terminal SF₅-group and possibly film structural anisotropy in the surface zone. Time-of-flight (TOF) secondary ion mass spectrometry (SIMS) analysis supplements the XPS data by showing the presence of all expected SF₅-acrylate chemistry components in the outer 15 Å of the film surface.     

The chemistry of chromyl fluoride III. Reactions with inorganic systems

Reactions of CrO₂F₂ with MF or MF₂ gave the corresponding M₂CrO₂F₄ and MCrO₂F₄ fluorochromates. With the Lewis Acids (SO₃, TaF₅, SbF₅) and (CF₃CO)₂O known and new chromyl compounds [CrO₂(CF₃COO)₂, CrO₂(SO₃F)₂, CrO₂FTaF₆, CrO₂FSbF₆, CrO₂FSb₂F₁₁] were produced. Chromyl fluoride and inorganic salts (CF₃COONa and NaNO₃) produced the following complexes - Na₂CrO₂F₂(CF₃COO)₂ and Na₂CrO₂F₂(NO₃)₂. Unusual solid products were obtained with CrO₂F₂ and NO, NO₂, SO₂.A new method of preparing CrO₂F₂ is also presented.     

Toward understanding the ionization of biomarkers from micrometer particles by bio-aerosol mass spectrometry

The appearance of informative signals in the mass spectra of laser-ablated bio-aerosol particles depends on the effective ionization probabilities (EIP) of individual components during the laser ionization process. This study investigates how bio-aerosol chemical composition governs the EIP values of specific components and the overall features of the spectra from the bio-aerosol mass spectrometry (BAMS). EIP values were determined for a series of amino acid, dipicolinic acid, and peptide aerosol particles to determine what chemical features aid in ionization. The spectra of individual amino acids and dipicolinic acid, as well as mixtures, were examined for extent of fragmentation and the presence of molecular ion dimers, which are indicative of ionization conditions. Standard mixtures yielded information with respect to the significance of secondary ion plume reactions on observed spectra. A greater understanding of how these parameters affect EIP and spectra characteristics of bio-aerosols will aid in the intelligent selection of viable future biomarkers for the identification of bio-terrorism agents.     

The addition of pentafluorosulfur bromide to fluoroolefins II

This paper reports the preparation, properties, and structure of new SF₅Br-fluoroolefin adducts. The extent and direction of SF₅Br addition to fluoroolefins have been studied with seven fluoroolefins. Steric factors appear to be important for this addition.     

Self-assembled organic monolayers terminated in perfluoroalkyl pentafluoro-lambda(6)-sulfanyl (-SF5) chemistry on gold

Recently synthesized (Winter, R.; Nixon, P. G.; Gard, G. L.; Radford, D. H.; Holcomb, N. R.; Grainger, D. W. J. Fluorine Chem. 2001, 107, 23-30) SF5-terminated perfluoroalkyl thiols (SF5(CF2)nCH2CH2SH, where n = 2, 4, and 6) and a symmetric SF5-terminated dialkyl disulfide ([SF5-CH=CH-(CH2)8-S-]2) were assembled as thin films chemisorbed onto gold surfaces. The adsorbed monolayer films of these SF5-containing molecules on polycrystalline gold were compared using ellipsometry, contact angle, X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (ToF-SIMS), and infrared spectroscopy (FTIR) surface analytical methods. The resulting SF5-dialkyl disulfide monolayer film shows moderate angle dependence in depth-dependent XPS analysis, suggesting a preferentially oriented film. The SF5-terminated perfluoroalkyl thiols exhibit angular-dependent XPS compositional variance depending on perfluoroalkyl chain length, consistent with improved film assembly (increasingly hydrophobic, fewer defects, and more vertical chain orientation increasing film thickness) with increasing chain length. Tof-SIMS measurements indicate that both full parent ions for these film-forming molecules and the unique SF5 terminal group are readily detectable from the thin films without substantial contamination from other adsorbates.     

The application of novel methodology for the synthesis of o-, m-, and p-(SF5-perfluoroethyl) benzene derivatives

The reaction of o-, m-, and p-F₂CCFC₆H₄X with SF₅Br produces an intermediate adduct, F₅SCF₂CFBrC₆H₄X, which, on treatment with AgBF₄, affords the first useful, high yield preparation of o-, m-, and p-F₅SCF₂CF₂C₆H₄X.     

Trifluoroethylene Sultone: Structure and Chemistry

The gas phase structure of trifluoroethylene sultone, ( 1 ) (3,4,4-trifluoro-1,2-oxathietane-2,2-dioxide) was determined by gas electron diffraction, and the four-membered ring was found to be planar. The following ring parameters (r_a distances and ∠_α angles with 3σ uncertainties) were derived in the electron diffraction analysis: C? O = 1.41 Å (ass.), C? C = 1.541(18) Å, S? O = 1.652(5) Å, S? C = 1.822(8) Å, S? C? C = 86.2(15)°, C? C? O = 97.1(28)°, C? O? S = 97.5(21)°, and O? S? C = 79.1(8)°. New spectral data (IR, NMR) of 1 , its acyclic isomer FSO₂CFHC(O)F ( 2 ), and the related anhydride, FSO₂OSO₂CFHC(O)F ( 3 ), are reported. New esters containing the fluorosulfonyl function, FSO₂CFHC(O)OCH₂CF₃ ( 4 ), FSO₂CFHC(O)OCH₂CH = CH₂ ( 5 ), and (FSO₂CFHC(O)OCH₂CH? CH₂? )_n ( 6 ) have been prepared and characterized.     

Uniform persistence for population interaction models with time delay

In this paper uniform persistence is establised for kolmogorov type Prey‐Predator and competion models with per capitals ent growth rates that are dependent on time‐lagged population densities.     

Structures and conformations of trifluoromethanesulfonic anhydride, (CF3SO2)2O, and bis(trifluoromethylsulfonyl)difluoromethane, (CF3SO2)2CF2

The geometric structures and conformational properties of trifluoromethanesulfonic anhydride, (CF₃SO₂)₂O, and bis(trifluoromethylsulfonyl)difluoromethane, (CF₃SO₂)₂CF₂ have been studied by gas electron diffraction (GED) and ab initio calculations (HF/3–21G*). The calculations predict for both systems two stable conformers with C₂ symmetry and one with C₁ symmetry. In both compounds structures with C₂ symmetry and dihedral angles SOSC ≈ 100° ((CF₃SO₂)₂O) and SCSC≈ 150° ((CF₃SO₂)₂CF₂ are lowest in energy. According to the GED analyses the dominant conformer of (CF₃SO₂)₂O₂ possesses C₂ symmetry with SOSC dihedral angles of 99.1(14)°. The presence of up to 30% of the two other conformers cannot be excluded; for (CF₃SO₂)₂CF₂ only one conformer with C₂ symmetry and SCSC dihedral angles of 143(2)° is observed. A complete set of geometric parameters is given.