Oxygen-containing Functionalities Research Articles

ToF SIMS and XPS Studies of Carbon Fiber Surface during Electrolytic Oxidation in 17O/18O Enriched Aqueous Electrolytes

Time-of-flight secondary ion mass spectrometry (ToF SIMS) has been applied in conjunction with isotope enrichment to investigate the chemical composition of the surface species of poly(acrylonitrile)-based carbon fibers, which were electrolytically oxidized in dilute hydrochloric acid solution in water with 17O/18O enrichment. The technique provides a tool with greater specificity and sensitivity to elemental species than X-ray photoelectron spectroscopy (XPS), in which the effects of the presence of the heavier isotopes on the modification to surface chemistry cannot be detected. Peaks associated with oxygen-containing functionalities, for example, m/z = 16 (O-), 17 (17O-, OH-), 18 (18O-,17OH-), and 19 (18OH-) were identified in negative ToF SIMS spectra of carbon fibers treated in isotope enriched solution. Only m/z = 16 (O-), 17 (17O-, OH-) were identified on carbon fiber surfaces treated in normal water. The concentrations of these surface species all showed an increasing trend with the level of treat...

Surface analyses of polyacrylonitrile-based activated carbon fibers by x-ray photoelectron spectroscopy

In this work, polyacrylonitrile (PAN)-based activated carbon fibers (ACFs) were developed by the common processes of stabilization, carbonization, and steam activation. Those fibers were successively subjected to heat treatment in a vacuum at high temperature and reactivation in steam. The changes in specific surface area and surface chemical characteristics were studied. The vaccum treatment reduced the surface area dramatically, while the surface nitrogen decreased after activation in steam and the surface oxygen was lowered upon the vaccum treatment. By curve-fitting the X-ray photoelectron spectroscopy (XPS) of C1s, O1s, and N1s, it was shown that the forms and compositions of the oxygen-containing functionalities seemed not to be affected significantly by the above-mentioned heat-treat-ment processes, whereas the nitrogen-containing functionalities showed some changes with these treatments. © 1996 John Wiley & Sons, Inc.

96/05743 Reliable chemical determination of oxygen-containing functionalities in coal and coal products. Carboxylic acid and phenolic hydroxyl functionalities

96/05743 Reliable chemical determination of oxygen-containing functionalities in coal and coal products. Carboxylic acid and phenolic hydroxyl functionalities

17O NMR spectroscopic investigation of steroids at natural abundance

AbstractNatural abundance 17O NMR spectroscopic data, in toluene‐d8 at 90°C, were obtained for different classes of steroids, including androstanes, estranes, pregnanes, cholanes and cholestanes. Only routine acquisition parameters were used in combination with linear prediction methods during the processing for eliminating acoustic ringing artifacts. The results are discussed in terms of stereochemical effects on the 17O chemical shift of the various oxygen‐containing functionalities.

Chemical structure and hydrocarbon formation of the Huanxian brown coal, China

The Huanxian brown coal of the Lower Tertiary of East China is taken as an example for the study of relationships between coal chemical structure and the mechanism of hydrocarbon formation. Maceral examination shows that the brown coal has a high liptinite (up to 20%), which includes alginites, resinites and sporinites. Fatty acids produced from potassium permanganate stepwise oxidation of the brown coal are mainly composed of normal and iso-branched saturated monocarboxylic (up to C 29) and dicarboxylic (up to C 9) acids. All of the aromatic acids are mono- or dibasic, and most have no more than two rings. The Py-GC fingerprint of this brown coal agreed well with the results of the oxidation. XRD and 13C NMR spectroscopic analyses show that the carbon aromaticity of the coal ranges from 0.54 to 0.59. In combination with the chemical analyses of the oxygen-containing functionalities, and 13C NMR measurements, various structural parameters and the carbon, oxygen and hydrogen atomic distributions of the brown coal were assessed. Artificial thermal maturation of the brown coal was carried out both by anhydrous and hydrous pyrolysis under different temperatures and times. Based on systematic analyses of the gaseous, liquid and solid products, a mechanism of oil and gas formation, related to the thermal evolution of the coal structure, is proposed.

Chemical reactions on plasma-treated polyethylene surfaces

Oxygen plasma treatment as a surface functionalization technique is discussed. Oxygen-containing functionalities were introduced on the surface of high- (HDPE) and low-density polyethylene (LDPE) by glow discharge. The number of surface hydroxyl groups was increased by a post-discharge wet treatment in a reducing solution. The effects of the substrate nature, the discharge parameters, and the post-discharge wet treatment on the surface functional groups are discussed, and the effectiveness of functionalized surfaces on the yield of coupling reactions is shown.

A novel surface treatment process for enhanced adhesion of ultra-high modulus polyethylene fibres to epoxy resins

Ultra-high modulus polyethylene (UHMPE) fibres have been treated using a novel 'non-plasma' treatment allowing the incorporation of various chemical functional groups onto the polymer surface. The process comprises two steps: corona discharge treatment, followed by silanization of the polymer surface by a solution of an organo-functional silane. Corona discharge treatment incorporates oxygen-containing functionalities, e.g. reactive hydroxyl groups, onto the polymer surface. The presence of reactive -OH groups provides the possibility of covalent linkage of any organo-functional silane to the corona discharge-treated polymer in the form of a fibre, film, sheet, or powder. The effectiveness of the process was assessed by examining the interlaminar fracture energy and flexural modulus and by SEM analysis of the fracture surfaces of composites fabricated from the untreated, corona discharge-treated, ammonia plasma-treated, and the amine-grafted (using the novel process) UHMPE fabric. A significant improvemen...

Core Level and Valence Band XPS Spectra of E-120 Pitch-based Carbon Fiber Galvanostatically Oxidized in (NH4)2CO3 Solution

Du Pont E-120 high modulus pitch-based carbon fiber was galvanostatically oxidized in (NH4)2CO3 solution and analyzed with both core level and valence band XPS. Compared to the untreated E-120 fiber, the galvanostatically oxidized fiber had a very much higher oxygen content on its surface. Nitrogen was also found on this carbon fiber sample after the treatment in (NH4)2CO3 solution but no nitrogen was found either before or after the treatment in HNO3 solution. Our previously reported work [see Y. Xie and P. M. A. Sherwood, Appl. Spectrosc. 43, 1153 (1989); Chem. Mater. 1, 427 (1989); 2, 293 (1990); Appl. Spectrosc. 44, 797 (1990); Chem. Mater. 3, 164 (1991); Appl. Spectrosc. 44, 1621 (1990); 45, 1158 (1991); Y. Xie, T. Wang, O. Franklin, and P. M. A. Sherwood, ibid. 46, 645 (1992)] showed that XPS valence band spectra were more sensitive to chemical environment on the carbon fiber surface than core level spectra and could be well interpreted by X–α calculations with model compounds. In this work, the valence band spectrum shows that there were three different types of oxygen-containing functional groups formed on the fiber surface when the fiber was electrochemically oxidized in (NH4)2CO3 solution but only one type of oxygen-containing functionality formed after the electrochemical treatment in HNO3 solution. We also reported [see Y. Xie and P. M. A. Sherwood, Appl. Spectrosc. 45, 1158 (1991)] that the reproducibility of the galvanostatic treatment was better than that of the potentiostatic treatment, although the results from potentiostatic oxidation and galvanostatic oxidation were very similar.

Core Level and Valence Band XPS Spectra of E-120 Pitch-based Carbon Fiber Potentiostatically Oxidized in (NH4)2CO3 Solution

Du Pont E-120 high modulus pitch-based carbon fiber was potentiostatically oxidized in (NH4)2CO3 solution and analyzed with both core level and valence band XPS. Compared to the untreated E-120 fiber, this electrochemically oxidized fiber had a much higher oxygen content on its surface. Nitrogen was also found on this carbon fiber sample after the treatment in (NH4)2CO3 solution, but no nitrogen was found either before or after the treatment in HNO3 solution. Our previously reported work [see Y. Xie and P. M. A. Sherwood, Chem. Mater. 1, 427 (1989); 2, 293 (1990); Appl. Spectrosc. 44, 797 (1990); Chem. Mater. 3, 164 (1991); Appl. Spectrosc. 44, 1621 (1990); 45, 1158 (1991); Y. Xie, T. Wang, O. Franklin, and P. M. A. Sherwood, ibid. 46, 645 (1992)] showed that XPS valence band spectra were more sensitive to chemical environment on the carbon fiber surface than core level spectra and could be well interpreted by X–α calculations with model compounds. In this work, the valence band spectrum shows that there were three different types of oxygen-containing functional groups formed on the fiber surface when the fiber was electrochemically oxidized in (NH4)2CO3 solution, but only one type of oxygen-containing functionality formed after the electrochemical treatment in HNO3 solution. We also reported [see Y. Xie and P. M. A. Sherwood, Appl. Spectrosc. 46, 1158 (1991)] that the reproducibility of the potentiostatic treatment was not as good as that of the galvanostatic treatment, although the results from potentiostatic oxidation and galvanostatic oxidation were very similar.

Oxygen‐plasma‐treated polypropylene interfaces with air, water, and epoxy resins: Part I. Air and water

AbstractOxygen plasma treatment of polypropylene (PP) surfaces led to introduction of oxygencontaining functionalities, with consequent improvement of surface wettability. A combination of X‐ray photoelectron spectroscopy (XPS), static secondary ion mass spectroscopy (SSIMS), and contact angle measurements (water‐in‐air and air‐in‐water) allowed us to characterize the behavior of the treated surface in contact with air (low‐energy surface) and water (high‐energy surface).The treated surface showed the tendency to rearrange itself to minimize its interfacial energy. When contacted with air (low‐energy surface), polar groups were buried away from the polymer/air interface, while in contact with water (high‐energy surface) polar groups remained at the polymer/water interface.When contacted with air, the polymer surface layer rearranged by macromolecular motions within itself, since interdiffusion with the bulk polymer seems forbidden. These motions are thermally activated and it was possible to obtain an apparent activation energy (58.1 kJ/mol) close to those reported for other vinyl polymers.

The effects of surface treatments of fibers on the interfacial properties in single-fiber composites

The interfacial properties between fibers and the matrix contribute to the overall properties in high performance composites. Plasma treatments (Ar, O2, CF4/O2, N2/H2) have been performed on carbon fibers to improve the fiber-matrix interaction. The treatment efficiency was checked by the single-fiber technique, while the surface chemistry and morphology were characterized by X-ray photoelectron spectroscopy (XPS), static secondary ion mass spectroscopy (SSIMS), and scanning electron microscopy (SEM). The O2- and N2/H2-plasma treatments proved most effective both for introducing oxygen-containing functionalities at the fiber surface and for improving the interfacial shear strength of carbon fiber/epoxy composites. A relationship between the oxygen concentration at the fiber surface and the interfacial shear strength is demonstrated.

Flavones ofMentha piperita of variety Kubanskaya 6

acetate of (III) (CDCI3), in comparison with the spectrum of the initial (III), showed the signals of two acetoxy groups. The UV spectra with diagnostic additives showed the presence of OH groups at C5 (36-nm shift due to sodium acetate) and C~' (50-nm shift due to sodium methanolate). No bathochromic shift of the band of (III) was observed in the presence of boric acid (ortho-dihydroxy grouping absent). In the presence of aluminum chloride with the addition of hydrochloric acid, the shift of the band of (III) was 26 nm, which is character- istic for a 5 hydroxyflavone having an oxygen-containing function in position 6.

Phytoecdysones of Serratula III. Mass spectrometric study of the acetates and acetonides of ecdysterone and viticosterone e

Features of the fragmentation of the side chain of the acetates and acetonides of ecdysterone and of viticosterone E have been studied. It has been shown that the presence of an oxygen-containing function at C25 in these compounds imparts to the spectra certain distinguishing features which have analytical value.

Mass spectrometry in structural and stereochemical problems–CXCIV: The mass spectrometric fragmentations of steroidal sapogenins

AbstractThe characteristic mass spectral fragmentation patterns of the basic structure of the steroidal sapogenin, (25R)‐5α‐spirostan, have been elucidated through the preparation of analogs with deuterium labels at positions 11, 12, 14, 15, 16, 17, 20, 21, 23, 24, 25, 26 and 27. In addition, the effects of a change of stereochemistry at positions 14 and 20, of the introduction of oxygencontaining functionalities mostly in ring F, and of the incorporation of olefinic unsaturation have been determined through synthesis of many examples.

NMR spectra of cardenolides with an oxygen-containing function at C10

The NMR spectra of 12 cardenolides with oxygen-containing functions at C10 has been studied. The chemical shifts of the signals of the protons of the C18 angular methyl group, a butenolide ring, and some other protons have been discussed as functions of the structural features of the individual compounds.